STOCK TPI HORSEPOWER LIMIT ?
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From: Belleville, IL USA
STOCK TPI HORSEPOWER LIMIT ?
First of all the simple answer:
No there is no limit.
First to address those people who follow the bigger orafice size is better law (hot rodder law #1).
A hole (orafice) will not flow any air at all without a pressure differential on each side of the orafice. For instance you either increase the relative pressure on one side, or lower the relative pressure on one side = bingo you have airflow. The rate of flow (known as CFM to hot-rodders) is primarily dependant on the difference in pressure on one side of the orafice VS the other side.
This means that you increase CFM by changing pressure. With a turbo/supercharger you can increase pressure on one side and increase CFM.
(note: this happens at the intake valve, NOT the throttle-body)
On the other hand, you can decrease the pressure in the chamber AND in the intake manifold by increasing the pull of the engine (vacuum producing capacity). The simple way to do this is simply increasing cubic inches.
CFM rating on carburetors etc. are based on 1.5 inches of mercury pressure drop (same as 0.7 psi below atmospheric pressure of 14.7psi or 29.93 inches of mercury). This means that an engine has to pull .7 psi at the throttle to flow enough air to equal the CFM rating of the carb or throttle body. This would leave about 14psi to feed the intake charge past the intake valve.
So does this mean that a little 500cfm two-barrel carburetor can flow over 1000cfm on the right engine?
ABSOLUTELY
The pull (vacuum) from the engine can be increased in several ways even without an increase in cubic inches. One of the biggest ways is through exhaust tuning or using the scavenging effect of headers to create a much much lower pressure in the chamber before the intake valve openning event.
Another way to increase pull is by changing the speed of the piston (other than RPM increase) at key points in the intake stroke cycle. The max piston speed is approximately midway on the piston stroke. Selection of crank-stroke and connecting rod length both affect the maximum piston speed. A faster piston speed will create more vacuum while the intake valve is open, and also create a stronger exhaust pulse for more scavenging effect. Valve events for intake & exhaust can be set to take advantage of this
(ie: Winston Cup).
A properly matched engine will put to shame your 330hp limit and silly calculations. Check out the real world.
Now for those that are screaming "hey wait a minute, that would increase CFM so the calculation is still correct"
Wrong again.
The amount of air and fuel consumed by an engine @WOT has no direct relation to power output at the crank or flywheel.
An example is in order.
Ok take your stock 305 and put in the junk long duration cam that lets a large percentage of air and fuel right out the exhaust due to excessive overlap. this means more air & fuel consumed but less power because less is burned in the chamber.
Another example,
This time two engines with identical camshafts and everything else except for the rods, crankshaft, and pistons. Even with equal cubic inches, the engine with the longer stroke would produce more power at the flywheel because of greatly increased mechanical leverage against the crank centerline.
The same amount of air & fuel can be burned in the chamber producing the same downward force on the piston, yet huge difference in power at the flywheel.
Leverage... check it out.
The engine that runs a longer connecting rod will also enjoy a leverage increase due to the rod/crank angle difference during the power stroke. Match this rod angle to your fuel burn rate to give you maximum cylinder pressure closer to the maximum leverage angle, and bingo = you have much more power.
one example: methanol burning engines.
Once again the stock TPI does not come into play because of any perceived reduction in CFM. By the way, what happened to Hot-Rod's calculation? they are physics experts aren't they?
Now as far as power to the rear wheels (the only thing that truly matters for performance), we have not even considered the increased leverage offered by the torque converter, transmission, or rear gears. It's starting to look like the TPI has little to do as far as limiting actual performance.
The TPI was a decent design in it's time that was shaped to produce good volumetric efficiency (& ramming effect) in the lower RPM range of the engine where a street car spends most of it's time. It works extremely well in the 3000-4000 RPM range where the shift recovery normally falls on a street car. A car that is set up to take advantage of this RPM range will perform great with a TPI.
The shape of a TPI will produce a curve in torque that peaks relatively low and falls off as RPM's climb. This torque fall-off is simply the characteristics of the TPI system and should not be viewed as any sort of limit.
A 400 cube engine will still have the potential to make more power with a stock TPI than a 305 cube engine (torque at a given RPM). Yes there are deminishing returns due to this fall-off at the higher RPM's. Even though torque at shift recovery is vastly more important to quick acceleration than horsepower at the top of the gear, it is very tempting to modify the stock TPI to reduce this high RPM fall-off.
Some people have limited success by simply upgrading induction parts to a larger size, but better results are achieved by changing their shape.
Shape is also a major factor on how many CFM's flow through an orafice of given size. A good induction shape will reduce the resistance to airflow and increase the velocity of the air.. thereby increasing CFM. This is a much better way of feeding an engine than simply openning up the orafice to a larger size which usually reduces velocity and can hurt CFM at certain RPM's in some cases.
A great example of improving orafice shape while maintaining it's approximate size:
Extrude Honing.
Even with CFM and leverage aside, there is still an even bigger factor to consider which also negates the theory of power limitation of a stock TPI. That factor is air density.
Even though you put a winston cup engine under the stock TPI you will reach some kind of limit on the dyno. This can be changed by modifying air density.
A big secret to getting the most from the TPI induction is the manipulation of air density. This is why it is so common for a well tuned TPI car to run 1/2 second faster in October than it did in July with only a difference in air density, and why an overly rich (the majority of cases) TPI car can gain up to a full second going from 90F degree air to 10F degree air. I have many many many vericom tests to back this up.
For you TPI owners. There are many tricks to increase air density in the TPI system, and if you look closely at the entire TPI you will see the factory has given you provisions that make this job easier.
Look in particular in the throttle-body and plenum areas.
hint #1 for runner ramming effect:
colder air is heavier with more momentum.
hint #2 for helmholtz effect:
pressure waves travel slower in denser air.
there goes your limitations. there goes your calculation. there goes Hot-Rod physics.
Have fun.
[This message has been edited by The ODB (edited February 23, 2001).]
No there is no limit.
First to address those people who follow the bigger orafice size is better law (hot rodder law #1).
A hole (orafice) will not flow any air at all without a pressure differential on each side of the orafice. For instance you either increase the relative pressure on one side, or lower the relative pressure on one side = bingo you have airflow. The rate of flow (known as CFM to hot-rodders) is primarily dependant on the difference in pressure on one side of the orafice VS the other side.
This means that you increase CFM by changing pressure. With a turbo/supercharger you can increase pressure on one side and increase CFM.
(note: this happens at the intake valve, NOT the throttle-body)
On the other hand, you can decrease the pressure in the chamber AND in the intake manifold by increasing the pull of the engine (vacuum producing capacity). The simple way to do this is simply increasing cubic inches.
CFM rating on carburetors etc. are based on 1.5 inches of mercury pressure drop (same as 0.7 psi below atmospheric pressure of 14.7psi or 29.93 inches of mercury). This means that an engine has to pull .7 psi at the throttle to flow enough air to equal the CFM rating of the carb or throttle body. This would leave about 14psi to feed the intake charge past the intake valve.
So does this mean that a little 500cfm two-barrel carburetor can flow over 1000cfm on the right engine?
ABSOLUTELY
The pull (vacuum) from the engine can be increased in several ways even without an increase in cubic inches. One of the biggest ways is through exhaust tuning or using the scavenging effect of headers to create a much much lower pressure in the chamber before the intake valve openning event.
Another way to increase pull is by changing the speed of the piston (other than RPM increase) at key points in the intake stroke cycle. The max piston speed is approximately midway on the piston stroke. Selection of crank-stroke and connecting rod length both affect the maximum piston speed. A faster piston speed will create more vacuum while the intake valve is open, and also create a stronger exhaust pulse for more scavenging effect. Valve events for intake & exhaust can be set to take advantage of this
(ie: Winston Cup).
A properly matched engine will put to shame your 330hp limit and silly calculations. Check out the real world.
Now for those that are screaming "hey wait a minute, that would increase CFM so the calculation is still correct"
Wrong again.
The amount of air and fuel consumed by an engine @WOT has no direct relation to power output at the crank or flywheel.
An example is in order.
Ok take your stock 305 and put in the junk long duration cam that lets a large percentage of air and fuel right out the exhaust due to excessive overlap. this means more air & fuel consumed but less power because less is burned in the chamber.
Another example,
This time two engines with identical camshafts and everything else except for the rods, crankshaft, and pistons. Even with equal cubic inches, the engine with the longer stroke would produce more power at the flywheel because of greatly increased mechanical leverage against the crank centerline.
The same amount of air & fuel can be burned in the chamber producing the same downward force on the piston, yet huge difference in power at the flywheel.
Leverage... check it out.
The engine that runs a longer connecting rod will also enjoy a leverage increase due to the rod/crank angle difference during the power stroke. Match this rod angle to your fuel burn rate to give you maximum cylinder pressure closer to the maximum leverage angle, and bingo = you have much more power.
one example: methanol burning engines.
Once again the stock TPI does not come into play because of any perceived reduction in CFM. By the way, what happened to Hot-Rod's calculation? they are physics experts aren't they?
Now as far as power to the rear wheels (the only thing that truly matters for performance), we have not even considered the increased leverage offered by the torque converter, transmission, or rear gears. It's starting to look like the TPI has little to do as far as limiting actual performance.
The TPI was a decent design in it's time that was shaped to produce good volumetric efficiency (& ramming effect) in the lower RPM range of the engine where a street car spends most of it's time. It works extremely well in the 3000-4000 RPM range where the shift recovery normally falls on a street car. A car that is set up to take advantage of this RPM range will perform great with a TPI.
The shape of a TPI will produce a curve in torque that peaks relatively low and falls off as RPM's climb. This torque fall-off is simply the characteristics of the TPI system and should not be viewed as any sort of limit.
A 400 cube engine will still have the potential to make more power with a stock TPI than a 305 cube engine (torque at a given RPM). Yes there are deminishing returns due to this fall-off at the higher RPM's. Even though torque at shift recovery is vastly more important to quick acceleration than horsepower at the top of the gear, it is very tempting to modify the stock TPI to reduce this high RPM fall-off.
Some people have limited success by simply upgrading induction parts to a larger size, but better results are achieved by changing their shape.
Shape is also a major factor on how many CFM's flow through an orafice of given size. A good induction shape will reduce the resistance to airflow and increase the velocity of the air.. thereby increasing CFM. This is a much better way of feeding an engine than simply openning up the orafice to a larger size which usually reduces velocity and can hurt CFM at certain RPM's in some cases.
A great example of improving orafice shape while maintaining it's approximate size:
Extrude Honing.
Even with CFM and leverage aside, there is still an even bigger factor to consider which also negates the theory of power limitation of a stock TPI. That factor is air density.
Even though you put a winston cup engine under the stock TPI you will reach some kind of limit on the dyno. This can be changed by modifying air density.
A big secret to getting the most from the TPI induction is the manipulation of air density. This is why it is so common for a well tuned TPI car to run 1/2 second faster in October than it did in July with only a difference in air density, and why an overly rich (the majority of cases) TPI car can gain up to a full second going from 90F degree air to 10F degree air. I have many many many vericom tests to back this up.
For you TPI owners. There are many tricks to increase air density in the TPI system, and if you look closely at the entire TPI you will see the factory has given you provisions that make this job easier.
Look in particular in the throttle-body and plenum areas.
hint #1 for runner ramming effect:
colder air is heavier with more momentum.
hint #2 for helmholtz effect:
pressure waves travel slower in denser air.
there goes your limitations. there goes your calculation. there goes Hot-Rod physics.
Have fun.
[This message has been edited by The ODB (edited February 23, 2001).]
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edited - reread post "silly" was meant to apply to calculations,,, which I pretty much agree with. Yes 330 horse mark can be put to shame,, even with a STOCK TPI. You make a good point, but I feel you know as well as I do few people are going to apply the principles you reference and run a STOCK TPI. Modified sure. Still think 330 horse is a good benchmark based on dyno pulls I've seen,, especially for a 350 in which the original post referenced with an unmodified STOCK TPI - diminishing returns.
Later.
[This message has been edited by BadSS (edited February 23, 2001).]
Later.
[This message has been edited by BadSS (edited February 23, 2001).]
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nah I meant no offense,
and I respect your opinions and experience too.
Deminishing returns is a major factor to deal with and nobody wants to pay the power price of making the engine produce vacuum at full throttle.
I was trying to put to rest the myth of power limits. I will be the first one to advise someone to stop messing around with TPI and go to a good carbureted setup (for several reasons).
There are just way too many people here that want to avoid optimizing and tuning by simply bolting on some bigger (big price) induction parts and expect X- amount of horsepower gain based simply on size/CFM rating.
I mostly blame the car magazines for the misunderstandings and myths going around through the years. Unfortunately if they told the complete truth their aftermarket advertising wouldn't make them so much money anymore.
As far as the horsepower numbers go, I mostly ignore them. The torque number is the only direct measurement of force at the crank or at the wheels. So even if an induction was limited somehow to 330hp, it still would not limit the performance of the vehicle.
Please, no disrespect intended, but I did think the 330hp number was a bit silly. I did not even remember that you had said it though, as I think I've seen it posted by others as well (in that range). Consider the word "silly" deleted.
In 94 my friend Shawn built a 383 with the camshaft I use today & AFR heads, then put a completely stock TPI on it with a 92-ECM (stock chip). He had very little money in the parts and it was far from being tuned or optimized. He ran TES headers, a 3" hi-flow cat, and walker cat-back.
It weighed 3500 lbs with driver and had a stock 700R & 2.73 gears. When he first ran it, it pulled 93mph trap speed with some spark-knock. He hollowed the hi-flow cat and immediately pulled 106 mph. Then he removed the muffler and went 108mph. On my mickey mouse calculator that is 350 horsepower... still with no tuning. He never touched the TPI. It was going to cost too much money to do what he wanted with the TPI, so he swapped to a carb setup like I run today. He also swapped to Hooker full-length headers & duals to the axle. If I remember right it then went 113mph with only tuning the distributor.
I think he feels the same way about TPI as I do... that it's not really a limit, but it is a pain and we don't want to run it.
I think before one considers the idea of deminishing returns for a stock TPI, they should think about switching to a different induction system that would save them much more money and hassle.
That same year I was running high 12's @102mph with my 305TPI +peanut cam. People would swear up and down that it's impossible. Not impossible, just not as easy.
deminishing returns... point taken.
ODB
and I respect your opinions and experience too.
Deminishing returns is a major factor to deal with and nobody wants to pay the power price of making the engine produce vacuum at full throttle.
I was trying to put to rest the myth of power limits. I will be the first one to advise someone to stop messing around with TPI and go to a good carbureted setup (for several reasons).
There are just way too many people here that want to avoid optimizing and tuning by simply bolting on some bigger (big price) induction parts and expect X- amount of horsepower gain based simply on size/CFM rating.
I mostly blame the car magazines for the misunderstandings and myths going around through the years. Unfortunately if they told the complete truth their aftermarket advertising wouldn't make them so much money anymore.
As far as the horsepower numbers go, I mostly ignore them. The torque number is the only direct measurement of force at the crank or at the wheels. So even if an induction was limited somehow to 330hp, it still would not limit the performance of the vehicle.
Please, no disrespect intended, but I did think the 330hp number was a bit silly. I did not even remember that you had said it though, as I think I've seen it posted by others as well (in that range). Consider the word "silly" deleted.
In 94 my friend Shawn built a 383 with the camshaft I use today & AFR heads, then put a completely stock TPI on it with a 92-ECM (stock chip). He had very little money in the parts and it was far from being tuned or optimized. He ran TES headers, a 3" hi-flow cat, and walker cat-back.
It weighed 3500 lbs with driver and had a stock 700R & 2.73 gears. When he first ran it, it pulled 93mph trap speed with some spark-knock. He hollowed the hi-flow cat and immediately pulled 106 mph. Then he removed the muffler and went 108mph. On my mickey mouse calculator that is 350 horsepower... still with no tuning. He never touched the TPI. It was going to cost too much money to do what he wanted with the TPI, so he swapped to a carb setup like I run today. He also swapped to Hooker full-length headers & duals to the axle. If I remember right it then went 113mph with only tuning the distributor.
I think he feels the same way about TPI as I do... that it's not really a limit, but it is a pain and we don't want to run it.
I think before one considers the idea of deminishing returns for a stock TPI, they should think about switching to a different induction system that would save them much more money and hassle.
That same year I was running high 12's @102mph with my 305TPI +peanut cam. People would swear up and down that it's impossible. Not impossible, just not as easy.
deminishing returns... point taken.
ODB
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Damn dude,,, tried to pull it before you replied to it. Sorry I edited,, I hate when folks do that after a post. Bad day at the office,, thought about it on the way home tried to pul it. I think we're pretty much on the same page.
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ok so ODB, you are running carb because it's simpler and cheaper to modifie? what about if $$ and easyness of mods wasn't an issue, I have the feeling you would still use TPI. would you?
Also, isn't that true that TPI gets better gas milage?
I just need to know...and how can the ford guys get so much better results than us with TPI? would you assume it's because the market is better for EFI fords fare as pricing and parts develeopement (good ford efi intake cost 500$ vs at least 800 to 1200 for TPI)??
Also, isn't that true that TPI gets better gas milage?
I just need to know...and how can the ford guys get so much better results than us with TPI? would you assume it's because the market is better for EFI fords fare as pricing and parts develeopement (good ford efi intake cost 500$ vs at least 800 to 1200 for TPI)??
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heeh, yeah I just saw that you misquoted me.
I said 330hp limit & silly calculations.
I was already appologizing..
man give me credit!
Ok let's just forget it then
I also have old-timerz
I said 330hp limit & silly calculations.
I was already appologizing..
man give me credit!
Ok let's just forget it then
I also have old-timerz
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From: Belleville, IL USA
<font face="Verdana, Arial" size="2">Originally posted by mirage2991:
ok so ODB, you are running carb because it's simpler and cheaper to modifie? what about if $$ and easyness of mods wasn't an issue, I have the feeling you would still use TPI. would you?
Also, isn't that true that TPI gets better gas milage?
I just need to know...and how can the ford guys get so much better results than us with TPI? would you assume it's because the market is better for EFI fords fare as pricing and parts develeopement (good ford efi intake cost 500$ vs at least 800 to 1200 for TPI)??</font>
ok so ODB, you are running carb because it's simpler and cheaper to modifie? what about if $$ and easyness of mods wasn't an issue, I have the feeling you would still use TPI. would you?
Also, isn't that true that TPI gets better gas milage?
I just need to know...and how can the ford guys get so much better results than us with TPI? would you assume it's because the market is better for EFI fords fare as pricing and parts develeopement (good ford efi intake cost 500$ vs at least 800 to 1200 for TPI)??</font>
I have recorded 33mpg highway on an 88 T/A with 305TPI with stock cam & stock exhaust.
The camshaft and exhaust actually play a much bigger role in fuel economy than using EFI or Carburetor.
When a good tuner gets control of the EFI, then yes it can make some more power and miles per gallon. The electronics also offers more versatility with dynamic tuning and support of boosted systems. It is far too expensive for me to do what I want with EFI though.
a good example:
Randy Eakins from Mo. is one of my local heros here. His corvette has a 400cid chevy and one big turbo with 15psi. He runs a custom EFI intake and the Fel-Pro EFI controls. The car is very mild and runs mid 7's @180 mph on gasoline.
If money were no object I think I might want something similar to that. I'd have to factor in about $10,000 for parts doing everything myself, and probably go through two engines during the tuning process.
Realistically it's not going to happen for me. I want other things more than I want the EFI.
Another issue is that I'm trying to base my future business on carb tuning & intake mods to give the budget racers a real source to turn to for performance to equal EFI.
It would look a little fishy if I were selling carburetors, but I ran EFI on my own car.
As far as ford EFI, it is really no better at all. The ford systems are just packaged a little better as a whole. I'm not sure which ford systems you are referring to. Personally I would never run a ford EFI even if it was given to me. I also run a carburetor on my mustang.
ODB
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<font face="Verdana, Arial" size="2">The amount of air and fuel consumed by an engine @WOT has no direct relation to power output at the crank or flywheel.
An example is in order.
Ok take your stock 305 and put in the junk long duration cam that lets a large percentage of air and fuel right out the exhaust due to excessive overlap. this means more air & fuel consumed but less power because less is burned in the chamber</font>
An example is in order.
Ok take your stock 305 and put in the junk long duration cam that lets a large percentage of air and fuel right out the exhaust due to excessive overlap. this means more air & fuel consumed but less power because less is burned in the chamber</font>
<font face="Verdana, Arial" size="2">Another example,
This time two engines with identical camshafts and everything else except for the rods, crankshaft, and pistons. Even with equal cubic inches, the engine with the longer stroke would produce more power at the flywheel because of greatly increased mechanical leverage against the crank centerline.
The same amount of air & fuel can be burned in the chamber producing the same downward force on the piston, yet huge difference in power at the flywheel.
Leverage... check it out.</font>
This time two engines with identical camshafts and everything else except for the rods, crankshaft, and pistons. Even with equal cubic inches, the engine with the longer stroke would produce more power at the flywheel because of greatly increased mechanical leverage against the crank centerline.
The same amount of air & fuel can be burned in the chamber producing the same downward force on the piston, yet huge difference in power at the flywheel.
Leverage... check it out.</font>
587 Hp that I'm putting in my car now, but the 377 with the bigger bore has much more airflow and RPM capability making it have more potential for overall peak HP numbers.
------------------
82 Z28 350, Ported #882 Heads, Performer RPM cam and intake, hedman headers,650 Demon carb,
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET: 12.52@107.2
Future plans: Dart headed, Roller cammed 383 in early '01
89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing
Mid Atlantic F Body -82 Z28 Page
R.I.P. Dale Earnhardt #3
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Damn ODB u should write a BOOK!! 
just kidding
------------------
92' camaro
New 305 block TPI conversion, Forged parts all around,Edelbrock intake,ported plennum,ported corvette alluminum heads, accel cam,52mm throttle bodie, SLP runners,ford SVO 19lb injectors,fuel regulator,cloys timing chain, comp alluminum roller rocker arms and pushrods MSD 8.5 mm wires, bosch plattinum plugs, hypertech cap & rotor and coil, Edelbrock TES headers, free flowing catalytic converter and a 3 inch force II flowmaster exhaust system.
Soon to come!!!
Procharger system 12lbs o boost.
Favorite quote: "where ever u go, there u are"
Other car;
1971 plymouth Duster
Mods:340,edelbrock victor jr. intake, 650 4 barrel holley, heddman headers,40 series dual flowmasters, cold air intake,4:10 gears, just got a new paint job and cragar rims with 315 tires in the back.
:Yeah its not a chevy but damn how many 71' dusters have u seen in the streets.
just kidding
------------------
92' camaro
New 305 block TPI conversion, Forged parts all around,Edelbrock intake,ported plennum,ported corvette alluminum heads, accel cam,52mm throttle bodie, SLP runners,ford SVO 19lb injectors,fuel regulator,cloys timing chain, comp alluminum roller rocker arms and pushrods MSD 8.5 mm wires, bosch plattinum plugs, hypertech cap & rotor and coil, Edelbrock TES headers, free flowing catalytic converter and a 3 inch force II flowmaster exhaust system.
Soon to come!!!
Procharger system 12lbs o boost.
Favorite quote: "where ever u go, there u are"
Other car;
1971 plymouth Duster
Mods:340,edelbrock victor jr. intake, 650 4 barrel holley, heddman headers,40 series dual flowmasters, cold air intake,4:10 gears, just got a new paint job and cragar rims with 315 tires in the back.
:Yeah its not a chevy but damn how many 71' dusters have u seen in the streets.
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please read a bit closer.
"have no DIRECT RELATION to power output"
that means as quantities of air & fuel go up, the power does not go up in direct proportion.
The chevy 302 is one of the biggest turd engines they ever produced to be a street engine. The 302 is a race design that can't get out of it's own way at street RPM's.
Find out for yourself. Take an 88 or so stock 305TPI car with 700R-4 and 2.73 rear ratio and see what it runs in the quarter. Then swap in the 302 with everything else the same (everything). The thing would be a complete joke.
Then put in a 383 and see what happens.
When we're talking about TPI induction, we're not talking about roundy-round racing... big difference.
The airflow potential from different bore size is very minimal compared to 25% more leverage applied to the crankshaft by using a 3.75" stroke.
The main advantage of a 302 would be its ability to spin faster with less inertial losses. That would only show up at very high RPM where it could make much higher horsepower simply because horsepower is derived from RPM IN A DIRECT RELATION.
Why be obsessed with horsepower? Isn't a quicker E.T. more important? or are you one of those people that want to launch their car off the 8000+ RPM rev limiter with slicks?
"have no DIRECT RELATION to power output"
that means as quantities of air & fuel go up, the power does not go up in direct proportion.
The chevy 302 is one of the biggest turd engines they ever produced to be a street engine. The 302 is a race design that can't get out of it's own way at street RPM's.
Find out for yourself. Take an 88 or so stock 305TPI car with 700R-4 and 2.73 rear ratio and see what it runs in the quarter. Then swap in the 302 with everything else the same (everything). The thing would be a complete joke.
Then put in a 383 and see what happens.
When we're talking about TPI induction, we're not talking about roundy-round racing... big difference.
The airflow potential from different bore size is very minimal compared to 25% more leverage applied to the crankshaft by using a 3.75" stroke.
The main advantage of a 302 would be its ability to spin faster with less inertial losses. That would only show up at very high RPM where it could make much higher horsepower simply because horsepower is derived from RPM IN A DIRECT RELATION.
Why be obsessed with horsepower? Isn't a quicker E.T. more important? or are you one of those people that want to launch their car off the 8000+ RPM rev limiter with slicks?
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From: Daytona beach, FL
so ODB, you think I'm waisting my time with TPI stuff? Frankly, I'm disapointed on the new intake I have put on...thank God I got it used...I ran so sh**y 2 weeks ago I came very close to either sale the darn thing or drop it from a cliff...maybe you can help me, all I want is a 13.7 consistant and on radials...my best was a 14.6 with a 2.0 60'prior the new intake...I'm about to change gears (3.73's to 3.23) and see what it'll do, but heack, if a carb still gets me 25mph on the interstate then I'm all about that...so can you give me a hand?
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85 Z28, 355, edelbrock base, SLP runners (old style) 58mmTB, ported plenum, stock cam, fuel reg, TES headers, flowmaster, 3.73's, shift kit, MSD 6a, 305 hypertech chip (YUUUCK!) best prior intake mods: 14.6 @ 94, 2.02 60' temp: 78deg, 80% moist, on radials.
69SS, black, 3,73's, TH400, 402 BB, roller everything (solid 246@50 622 lift)+stud-guirdle, 67 Vette heads ported and o-ringed, about 10:1 cr KB pistons, should be done this summer, goals: 500hp and lots of fun
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85 Z28, 355, edelbrock base, SLP runners (old style) 58mmTB, ported plenum, stock cam, fuel reg, TES headers, flowmaster, 3.73's, shift kit, MSD 6a, 305 hypertech chip (YUUUCK!) best prior intake mods: 14.6 @ 94, 2.02 60' temp: 78deg, 80% moist, on radials.
69SS, black, 3,73's, TH400, 402 BB, roller everything (solid 246@50 622 lift)+stud-guirdle, 67 Vette heads ported and o-ringed, about 10:1 cr KB pistons, should be done this summer, goals: 500hp and lots of fun
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From: Belleville, IL USA
<font face="Verdana, Arial" size="2">Originally posted by mirage2991:
so ODB, you think I'm waisting my time with TPI stuff? Frankly, I'm disapointed on the new intake I have put on...thank God I got it used...I ran so sh**y 2 weeks ago I came very close to either sale the darn thing or drop it from a cliff...maybe you can help me, all I want is a 13.7 consistant and on radials...my best was a 14.6 with a 2.0 60'prior the new intake...I'm about to change gears (3.73's to 3.23) and see what it'll do, but heack, if a carb still gets me 25mph on the interstate then I'm all about that...so can you give me a hand?
</font>
so ODB, you think I'm waisting my time with TPI stuff? Frankly, I'm disapointed on the new intake I have put on...thank God I got it used...I ran so sh**y 2 weeks ago I came very close to either sale the darn thing or drop it from a cliff...maybe you can help me, all I want is a 13.7 consistant and on radials...my best was a 14.6 with a 2.0 60'prior the new intake...I'm about to change gears (3.73's to 3.23) and see what it'll do, but heack, if a carb still gets me 25mph on the interstate then I'm all about that...so can you give me a hand?
</font>
Yes I will help you if you plan to run a dualplane intake and Edlebrock carb. It will save you a lot of money in the long run, and i would expect better than 13's with the right exhaust & tires.
You say you have an 85 with a 355 & stock camshaft. What year & type camshaft would that be?
Member
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From: Sarasota, FL
My experience - I switched from a ported stock TPI to a ported Edelbrock TPI and saw a 8% flow gain. This comes mostly from increased runner diameter. The theory that the TPI has no power limits is sound, but that is not to say that it doesn't suck for racing. That thing will knock a 400 hp motor down to 300, but will increase torque with all the velocity that comes from small runners. The shape is not condusive to flow either. Torque is great for the street, but 1/4 mile winning hp comes from revs. Square engines are great on the street, but large bore short stroke engines usually always win high rpm contests. Longer rod length is not always better either. It breathes better at upper rpms, but stalls out at lower rpms. Next, good carb tuning can keep up with EFI, but good EFI tuning beats good carb tuning. Someone who knows engines and learns EFI can do wonders with the stock computer and customized chip.
My solution? Well, the LTR route is great for torque, but is not good for high rpm power because of shape. SuperRam is a good compromise, but $1200, c'mon. I'm either going to build some big plenum, short runner intake to fit the current base (which actually flows well) or adapt a dual plane manifold to EFI.
My solution? Well, the LTR route is great for torque, but is not good for high rpm power because of shape. SuperRam is a good compromise, but $1200, c'mon. I'm either going to build some big plenum, short runner intake to fit the current base (which actually flows well) or adapt a dual plane manifold to EFI.
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Joined: May 2000
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From: Daytona beach, FL
ODB, for the cam, I wish I knew, my friend from whom I baught the car doesn't remember the specs, he did say it was a roller (which I know it's true aftert pulling the intake) and that it's from GM....he ask GM for the "biggest TPI cam"...what ever that means...it idles like stock, and won't go past 5000rpms, maybe 5200 on a cold day...but judging by the performance, I'd say it's your basic 203/403 lift cam...and also I kind of wish I had changed the cam to better match the new intake....but if you can get me in the 13's with dual plane intake and a carb with my stock cam and heads (oh yea, they are not L98, but 882's) and still keep about 20 to 25 mpg, I'm all about that!
Member
Joined: Jul 1999
Posts: 496
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From: Chicago, IL
Car: 89 IROC-Z
Engine: LB9
Transmission: 700-R4
ODB, Basett, and others,
It doesn't seem like you all are in conflict at all. But I have some questions - I already posted a few on the exhaust and brake boards. I have an 89 LB9 Iroc (700R4, 2.73 posi, rear drums, etc.) I've got a full 3" exhaust (no cat) after the manifolds (headers on the way) decent HR4 tires, perfomance suspension parts, tb bypass, afpr, gutted maf, minor weight reduction, yatta yatta. I plan to do some really trick stuff with the exhaust and intake. I plan to have a shop hone out my tb to 51.5mm or so - is there any better shape than "round" for this piece? I'm fairly sure trapezoidal is out of the question I will also port my plenum soon and may have a shop fab up some bigger runners or maybe even a special plenum/runner combo. My goal is an N/A daily driven Iroc that gets 25-30 highway mpg and will go high 11's/low 12's under good track conditions. Oh, I also plan to ditch the 305 eventually unless I can somehow beyond hope get my current motor to hit those numbers....this is just type to fill up space so that while you're laughing you don't miss anything important... 
Well, thanks for any replies and thanks for all the good tech info you guys!
------------------
"We lost Dale. This isn't fun anymore"
R.I.P. #3
"The inevitability of death serves as the most clear evidence that to truly live, one must constantly court death, flaunt death, smack death around, and basically grab death by the throat and dare it to come too soon."
- Me
It doesn't seem like you all are in conflict at all. But I have some questions - I already posted a few on the exhaust and brake boards. I have an 89 LB9 Iroc (700R4, 2.73 posi, rear drums, etc.) I've got a full 3" exhaust (no cat) after the manifolds (headers on the way) decent HR4 tires, perfomance suspension parts, tb bypass, afpr, gutted maf, minor weight reduction, yatta yatta. I plan to do some really trick stuff with the exhaust and intake. I plan to have a shop hone out my tb to 51.5mm or so - is there any better shape than "round" for this piece? I'm fairly sure trapezoidal is out of the question
I will also port my plenum soon and may have a shop fab up some bigger runners or maybe even a special plenum/runner combo. My goal is an N/A daily driven Iroc that gets 25-30 highway mpg and will go high 11's/low 12's under good track conditions. Oh, I also plan to ditch the 305 eventually unless I can somehow beyond hope get my current motor to hit those numbers....this is just type to fill up space so that while you're laughing you don't miss anything important... Well, thanks for any replies and thanks for all the good tech info you guys!------------------
"We lost Dale. This isn't fun anymore"
R.I.P. #3
"The inevitability of death serves as the most clear evidence that to truly live, one must constantly court death, flaunt death, smack death around, and basically grab death by the throat and dare it to come too soon."
- Me
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From: Belleville, IL USA
I'm not laughing at all because I know you can do it. I will tell you what I've done in the past and give you ideas for a new intake design to try since you're going to be doing some fabbing anyway.. nothing major though.
<font face="Verdana, Arial" size="2">The chevy 302 is one of the biggest turd engines they ever produced to be a street engine. The 302 is a race design that can't get out of it's own way at street RPM's. </font>
<font face="Verdana, Arial" size="2">
The engine that runs a longer connecting rod will also enjoy a leverage increase due to the rod/crank angle difference during the power stroke. </font>
The engine that runs a longer connecting rod will also enjoy a leverage increase due to the rod/crank angle difference during the power stroke. </font>
BTW, I'm not a 302 zealot, just trying to learn something.
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From: Belleville, IL USA
they aren't much different, and the rod length is good, but no where near the difference that stroke length makes. The final mechanical leverage ratio is determined by the stroke.
The ford 302 is also a turd engine that needs a light car, low gears, long runner EFI, and headers to even run halfway decent as a street engine.
Imagine the 5.0 liter mustang GT with an automatic transmission, then add 200 extra pounds to equal the fbody, then put on log-style exhaust manifolds & Y-pipe to single exhaust. Then put in the 2.73:1 rear ratio, and see how it fares in the quarter mile against the chevy 305 in the same trim.
If you have half a day to kill as you watch the short-stroke wonder muscle its way down the track you will see exactly what I'm saying as it applies to a street car.
Giving away leverage is like trying to use a weedwacker engine to power your riding lawnmower. No matter how good the weedwacker is designed, or how much high RPM horsepower it makes, it would be a joke trying to power a riding lawnmower.
If you give away leverage inside the engine, then you just have to make it up somewhere else (usually gears & high RPM). That's why the 302 chevy cars run 5-series gears and turn over 8-grand. In street trim (from factory) they could NOT get out of their own way..
and that cannot be blamed on the polyglass tires either because the cars pulled no trap-speed to show any power. They spun, hooked & then bogged.
The ford 302 is also a turd engine that needs a light car, low gears, long runner EFI, and headers to even run halfway decent as a street engine.
Imagine the 5.0 liter mustang GT with an automatic transmission, then add 200 extra pounds to equal the fbody, then put on log-style exhaust manifolds & Y-pipe to single exhaust. Then put in the 2.73:1 rear ratio, and see how it fares in the quarter mile against the chevy 305 in the same trim.
If you have half a day to kill as you watch the short-stroke wonder muscle its way down the track you will see exactly what I'm saying as it applies to a street car.
Giving away leverage is like trying to use a weedwacker engine to power your riding lawnmower. No matter how good the weedwacker is designed, or how much high RPM horsepower it makes, it would be a joke trying to power a riding lawnmower.
If you give away leverage inside the engine, then you just have to make it up somewhere else (usually gears & high RPM). That's why the 302 chevy cars run 5-series gears and turn over 8-grand. In street trim (from factory) they could NOT get out of their own way..
and that cannot be blamed on the polyglass tires either because the cars pulled no trap-speed to show any power. They spun, hooked & then bogged.
Member
Joined: Oct 2000
Posts: 385
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From: San Antonio, TX
Posted by mirage2991
mirage,
you should install an exhaust cutout, BUT RIGHT BEFORE the catalytic converter. This mod alone is worth 2 tenths on my car (very similar to your, except I have a good size cam). The 58mm TB is hurting you, just like it is hurting me by at least a thenth (maybe more in your engine with stock cam). I really don't like the Edelbrock headers, they look very restrictive to me. Hedman or Hooker headers are definately better, but the TES are still better than stock manifolds. I don't know much about programming, but I guess the 305 chip might be hurting performance as well. Your gears should get you off the line really quick; I say that with a stock or no bigger than 52mm TB, an exhaust cutout, timing set at 7-8* (whatever works best) a stock or custom 350 chip and good traction; you should definately see 13.8 at something like 98-100 MPH. If that doesn't happen, either your engine is hurt (pistons, compression leak, etc) or you live in Mt. Everest where air is really thin.
Rick
------------------
'88 GTA 350
Headers, catback, free mods, Xtreme energy cam, intake pieces and 2100 RPM TQ
13.39@102.50 MPH
1.90 Sec ------- Best 60FT
104.23 MPH -- Best Trap Speed
AIM HIGH!
<font face="Verdana, Arial" size="2"> so ODB, you think I'm waisting my time with TPI stuff? Frankly, I'm disapointed on the new intake I have put on...thank God I got it used...I ran so sh**y 2 weeks ago I came very close to either sale the darn thing or drop it from a cliff...maybe you can help me, all I want is a 13.7 consistant and on radials...my best was a 14.6 with a 2.0 60'prior the new intake </font>
you should install an exhaust cutout, BUT RIGHT BEFORE the catalytic converter. This mod alone is worth 2 tenths on my car (very similar to your, except I have a good size cam). The 58mm TB is hurting you, just like it is hurting me by at least a thenth (maybe more in your engine with stock cam). I really don't like the Edelbrock headers, they look very restrictive to me. Hedman or Hooker headers are definately better, but the TES are still better than stock manifolds. I don't know much about programming, but I guess the 305 chip might be hurting performance as well. Your gears should get you off the line really quick; I say that with a stock or no bigger than 52mm TB, an exhaust cutout, timing set at 7-8* (whatever works best) a stock or custom 350 chip and good traction; you should definately see 13.8 at something like 98-100 MPH. If that doesn't happen, either your engine is hurt (pistons, compression leak, etc) or you live in Mt. Everest where air is really thin.
Rick
------------------
'88 GTA 350
Headers, catback, free mods, Xtreme energy cam, intake pieces and 2100 RPM TQ
13.39@102.50 MPH
1.90 Sec ------- Best 60FT
104.23 MPH -- Best Trap Speed
AIM HIGH!
Thread Starter
Banned
Joined: Jan 2001
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From: Belleville, IL USA
<font face="Verdana, Arial" size="2">Originally posted by I ROCK:
I already posted a few on the exhaust and brake boards. I have an 89 LB9 Iroc (700R4, 2.73 posi, rear drums, etc.) I've got a full 3" exhaust (no cat) after the manifolds (headers on the way) decent HR4 tires, perfomance suspension parts, tb bypass, afpr, gutted maf, minor weight reduction, yatta yatta. I plan to do some really trick stuff with the exhaust and intake. I plan to have a shop hone out my tb to 51.5mm or so - is there any better shape than "round" for this piece? I'm fairly sure trapezoidal is out of the question I will also port my plenum soon and may have a shop fab up some bigger runners or maybe even a special plenum/runner combo. My goal is an N/A daily driven Iroc that gets 25-30 highway mpg and will go high 11's/low 12's under good track conditions. Oh, I also plan to ditch the 305 eventually unless I can somehow beyond hope get my current motor to hit those numbers....
</font>
I already posted a few on the exhaust and brake boards. I have an 89 LB9 Iroc (700R4, 2.73 posi, rear drums, etc.) I've got a full 3" exhaust (no cat) after the manifolds (headers on the way) decent HR4 tires, perfomance suspension parts, tb bypass, afpr, gutted maf, minor weight reduction, yatta yatta. I plan to do some really trick stuff with the exhaust and intake. I plan to have a shop hone out my tb to 51.5mm or so - is there any better shape than "round" for this piece? I'm fairly sure trapezoidal is out of the question
I will also port my plenum soon and may have a shop fab up some bigger runners or maybe even a special plenum/runner combo. My goal is an N/A daily driven Iroc that gets 25-30 highway mpg and will go high 11's/low 12's under good track conditions. Oh, I also plan to ditch the 305 eventually unless I can somehow beyond hope get my current motor to hit those numbers....</font>
I'm with you on these mods. I will say to save your money on the throttlebody unless you step up to a 383.. then just buy the big one.
There are much bigger fish to fry with the TPI than a little diameter increase at the TB. The two round holes are actually pretty efficient in shape. Two small holes reduce the strength of reversion past the TB. One bigger hole or two-bigger holes allow much more reversion.
Extending the divider is a bigger issue for tuning the pulses.
I highly suggest swapping to a newer 1992 ECM and running a MAP only. This will make your life much easier, and give you huge leway in designing your intake and induction tubing.
You then may use a helmholtz taper or play with radius & pipe length on your intake feed tube.
When you get tuned pulses, reduced reversion, and control over the air density, then the actual size of the throttle blades will play little part in limiting the engine. It becomes a different story with a 383 or larger though. In that case I would just switch to a stock LS1 throttle body and adapt it.
To get the most out of a stock TB you can still narrow the throttle shafts, and grind the throttle stop for full 90* opening. The biggest improvement would be to radius the entry though. This means using a much larger air feed tube. (hence the need for no MAF).
So far I've just barely touched on what can be done, but email me for more info. I want to avoid a lot of arguing on here. Get ahold of me before you port your plenum or fab runners.
ODB
daodb@yahoo.com
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Joined: May 2000
Posts: 157
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From: Daytona beach, FL
Raptor, I'm not running any cats at all, just a 3" pipe (well more like 2.3/4) down to a flowmaster. I don't think the engine is "hurt" it has 38,000miles on it, 6 pass down the strip, mostly highway miles, it pulls really good down low, it just doesn't have any top end past 4800 (won't go past 5k). On a cold day, I can get 2nd up to 5200, but I think I get better results shifting at ring on 4700.
I want to swap ECM and go either 86 and up or map, I'm ECM hunting right now. In any case, I'm still changing gears and puting my disc break rear that has 3.23's in it. I could atempt to re-install the stock TB and see what it does. And like I say I have the sh*tiest heads on that motor anyway. (882's). If a stock 90 Z28 can run 13.8, with no mods but a chip and K&N, then so can I...darn it!
What I mean by old style SLP runners is that 2 of the runners, I think driver side back and passenger side front have no deviders in them, while in the newer castings, SLP has all the runners with deviders. I did massage them a bit and port mtached them to my edelbrock base and to the plenum (well I need to massage the plenum a bit more). I did notice a serious problem hooking up, even by being gentle (to read "launch like a grany") but didn't see no MPH imprvements (but 0.18mph) so that mean no power increase at all...and for 3 days worth of work I'm very disapointed. beside that the car runs great, no troubles, no nothing, she just doesn't wanna run the times it should. Oh and I get really agravated when my friend and his 5.0 with also sh*ty heads and a small cam (208 and 520 lift) pulls high 13's all day long...good thing he is my friend! lol. ALL I want is 13.7 consistend on radials...now how hard can this be?
I want to swap ECM and go either 86 and up or map, I'm ECM hunting right now. In any case, I'm still changing gears and puting my disc break rear that has 3.23's in it. I could atempt to re-install the stock TB and see what it does. And like I say I have the sh*tiest heads on that motor anyway. (882's). If a stock 90 Z28 can run 13.8, with no mods but a chip and K&N, then so can I...darn it!
What I mean by old style SLP runners is that 2 of the runners, I think driver side back and passenger side front have no deviders in them, while in the newer castings, SLP has all the runners with deviders. I did massage them a bit and port mtached them to my edelbrock base and to the plenum (well I need to massage the plenum a bit more). I did notice a serious problem hooking up, even by being gentle (to read "launch like a grany") but didn't see no MPH imprvements (but 0.18mph) so that mean no power increase at all...and for 3 days worth of work I'm very disapointed. beside that the car runs great, no troubles, no nothing, she just doesn't wanna run the times it should. Oh and I get really agravated when my friend and his 5.0 with also sh*ty heads and a small cam (208 and 520 lift) pulls high 13's all day long...good thing he is my friend! lol. ALL I want is 13.7 consistend on radials...now how hard can this be?
Joined: Jul 2000
Posts: 6,530
Likes: 94
From: Aridzona
Car: `86 SS / `87 SS
Engine: L69 w/ TPI on top / 305 4bbl
Transmission: `95 T56 \ `88 200-4R
mirage,
Part of your problem is the cam. Factory cams have an odd exhaust lobe closing ramp that kinda halfass tries to induce an EGR function.
I would first step up the cam & do some porting of the base.
As already stated, the 58mm is overkill and isn't helping. Have you seen the L98 TB on the GM Ram-Jet 502? 502hp says you have too much TB for a 355. (Maybe the 502 doesn't have enough TB, but anyway...)
You aren't wasting your time w/ TPI stuff The mileage won't require tons of time to get, as it will w/ a carb.
Definitely consider further porting of the base if you haven't already.
Why are you changing for 3.23's if your goal is 1/4 mile times? IMHO, you're wasting your time; the incremental mileage gain doesn't offset things. For goodness sake, say you have overdrive. Ah... for disk brakes? Get the 3.73's put in the disc rear.
But really... you change cams from a factory GM TPI cam and you're going to gain 4/10, I would think, no problem.
Cam, Cam, Cam!!!!!!!!!!
------------------
jmd
L69 / T5
Part of your problem is the cam. Factory cams have an odd exhaust lobe closing ramp that kinda halfass tries to induce an EGR function.
I would first step up the cam & do some porting of the base.
As already stated, the 58mm is overkill and isn't helping. Have you seen the L98 TB on the GM Ram-Jet 502?
502hp says you have too much TB for a 355. (Maybe the 502 doesn't have enough TB, but anyway...)You aren't wasting your time w/ TPI stuff The mileage won't require tons of time to get, as it will w/ a carb.
Definitely consider further porting of the base if you haven't already.
Why are you changing for 3.23's if your goal is 1/4 mile times? IMHO, you're wasting your time; the incremental mileage gain doesn't offset things. For goodness sake, say you have overdrive. Ah... for disk brakes? Get the 3.73's put in the disc rear.
But really... you change cams from a factory GM TPI cam and you're going to gain 4/10, I would think, no problem.
Cam, Cam, Cam!!!!!!!!!!
------------------
jmd
L69 / T5
Last edited by jmd; Feb 18, 2014 at 09:47 PM.
Member
Joined: May 2000
Posts: 157
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From: Daytona beach, FL
well, my reasoning for the 3.23's is that I'll hook up a bit more, and it won't put me out of the power band. Also, seing a 90Z28 with 3.23', no headers, cat back and chip turning 13.9 with stikcy tires really agravates me...even if I did pull a 1.9 or 1.8, no way the car would go faster than 14.2...also, the steapest gear doesn't mean you'll be better off...my friend is the prime exemple (see above posts...)...also, before I spend $$ on that rear, I want to try it out...if 3.23's don't help, then I'll stick my 3.73's in it...it's not like I'm thrawing away those gears...I'm keeping all that...just the old rear and that nasty bearing is going "bye bye"...not the internals...
Cam, indeed, I wish I had done it while doing the intake....oh boy I wish I did, a nice LT4 hot cam, something with like 214 or 218 duration and some 480 lift...keep it on the mild side, just so I can run 13.7 13.5 all day...after all it's my daily driver...
but like I said, the rear is going in this saturday...I'll let you guys know the pros and cons...also, one more thing I'm gonna check out, the fuel pump...it's not holding pressure, and no it's not my injectors, it did it with the old ones and the new ones...I got to check it out at WOT see what pressure it holds....
Cam, indeed, I wish I had done it while doing the intake....oh boy I wish I did, a nice LT4 hot cam, something with like 214 or 218 duration and some 480 lift...keep it on the mild side, just so I can run 13.7 13.5 all day...after all it's my daily driver...
but like I said, the rear is going in this saturday...I'll let you guys know the pros and cons...also, one more thing I'm gonna check out, the fuel pump...it's not holding pressure, and no it's not my injectors, it did it with the old ones and the new ones...I got to check it out at WOT see what pressure it holds....
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From: Belleville, IL USA
I agree the TB is overkill, but I don't agree with the cam.
If you put in a big turdstick cam then yeah you will need more rear gear.
If you keep the stock cam, then the 3.23's should be great.
I saw you post about swapping heads. Generally long duration on a cam is a band-aid fix for poor flowing heads. With good heads you have less need for long duration.
Good valve lift (especially over .500) is important to make good on aftermarket heads. Easy to get the lift using rocker ratio rather than over-doing the duration.
If you go aluminum heads, then get very tight chambers and run at least 11:1 if possible. That plus high valve lift will give you very large power gains of 50hp or more, but without the bad side-effects of the long duration camshaft, or the need for more gear.
IMO
If you put in a big turdstick cam then yeah you will need more rear gear.
If you keep the stock cam, then the 3.23's should be great.
I saw you post about swapping heads. Generally long duration on a cam is a band-aid fix for poor flowing heads. With good heads you have less need for long duration.
Good valve lift (especially over .500) is important to make good on aftermarket heads. Easy to get the lift using rocker ratio rather than over-doing the duration.
If you go aluminum heads, then get very tight chambers and run at least 11:1 if possible. That plus high valve lift will give you very large power gains of 50hp or more, but without the bad side-effects of the long duration camshaft, or the need for more gear.
IMO
Member
Joined: May 2000
Posts: 157
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From: Daytona beach, FL
how bad can that 58mm hurts me? not 4 tenth!. I"m begining to thing that my 882's heads are what's the problem...what do you guys think? after all those heads were made in very early 80's, smog, and during the period of low power V8's....
(by the way, didn't mean to turn this post in a personal issue....)
(by the way, didn't mean to turn this post in a personal issue....)
mirage Id say its the valvesprings in those heads. They are probably original. I had a stock l98 cam in my 383 originally and it would run up to 5500. Those heads are killing compression and power. They make good anchors.
------------------
87z 383,afr 190's, comp hyd roller(242/248-.540/.562,114 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, tremec 5spd, , 1,3/4" slp headers, speed pro bank to bank-wb02.
"Just remember children, no man can beat you once youv'e found the cliterous." 'chef'
------------------
87z 383,afr 190's, comp hyd roller(242/248-.540/.562,114 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, tremec 5spd, , 1,3/4" slp headers, speed pro bank to bank-wb02.
"Just remember children, no man can beat you once youv'e found the cliterous." 'chef'
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