Nelz

Many people on the board have found and fixed many of the weaknesses of our cars, especially as the years have gone by and we start watching newer vehicles including some fast stock imports beat us.

My 1988 Iroc still turns heads, but in performance with the stock LB9 and T-5WC it just doesn't cut it anymore. So the logical thing to do was to correct this vehicle of all it's weaknesses. Here they are:

The Limits of the Car include:

Air:
Throttle body= 48mm = 630 cfm = 325 HP
Heads: Stop flowing at .500 lift at about 195cfm I and 110 cfm E on a 305 based on another thread https://www.thirdgen.org/forums/tech...6-airflow.html

Intake: Stock TPI runners and manifold work to make peak torque from 2000rpm-4000rpm and peak HP at 4800RPM.

Fuel:
Injectors = 19lb. (BHPx BSFC)/no. injectors x 0.8 = Injector size
Assume BSFC of 0.47 and do some algebra
(BHP x 0.47)/8 x 0.8 = 19
=BHP0.47= 19(8x.08)
=BHP= 19(8x0.8)/0.47 = 259 HP <--This is the weakest Link that will hold you back. Requires Injector and computer change.)

The 5.0 injector delivers 19lb/hr at 36PSI Stock. If I boosted PSI by 10% to 40PSI, new rate would be 20lb/hr. 20(8x0.8)/0.47= 272 hp. So I could just bump up fuel pressure and raise the limit of HP by 13 horses. THE BSFC number is a large factor and determines how much fuel the engine will consume. If it is a 0.5 BSFC then even with this mod, the max will be 256 hp and stock would be 243 HP. If it was a really efficient engine, stock limit at 0.45BSFC would be 270.22 and modded would be 284HP. Make sure I can keep the BSFC down by making the engine very efficient. The Something Old Something new engine in GM high Tech Nov. 2006 had a BSFC of 0.4.

Heads/Compression limit:
airflow @ 28in. H20 x 0.257 x # cylinders = power

Stock heads flow 195 I and 110 on E. On the intake, heads support 400HP and exhaust support 226 HP. (I may be wrong on the following calculation, but add 400HP and 226HP and divide by 2 and you get an average limit of 313HP)

Vortec Heads on the otherhand peak at 239 cfm on the intake so 491 HP on the intake and on the exhaust 151cfm so 330HP on the exhaust. Add and divide those two numbers and you get 400HP (which is what every magazine averges with those heads).

Mechanical:
Transmission =300ft.lbs TQ
Rear End= 400ft. Lbs TQ.
Cast Iron bottom end = limit is 6034 RPM assuming a safe maximum of 3500 foot per minute limit in piston speed. (Based on an old engineering textbook.) This will limit where you can shift and the gearing.


Electronic
Stock prom will compensate fuel pressure change up to 15% but after that, will skew the fuel curve enough to harm performance unless calibration is changed. (I run a MAF, speed density systems may have less room to move around.)

Weight: The car weighs 3218lbs after I lightened it (and without me in it.) With 220hp stock, I'm carrying almost 15lbs/hp. Contrast that with a 2004 z06 at 7.7lb/hp or a 2009 Nissan 370Z at 9.56lbs/hp and I either need to lighten this car by another 1000lbs to hit the magic 10/1 number or I boost hp by 110 horses.


So the cure:
Define the purpose of my car and it's intended usage based on the following principle:
"Build the car around it's intended use and maximize torque in the RPM area where it will spend most of it's time during that use.
Use that as the foundation to making the car quicker." -John Ligenfelter. (He was talking about boosting power at where the engine spends most of it's time in RPM when drag racing a stock Corvette. Which was about 4000-5000rpm.)

What then is the definition of a street engine?
-It gets relatively good gas mileage
-It is durable and maintenance free (trust me on this one, my last road trip I was stranded in a hot Iroc that needed a jump everytime I shut the motor off in a remote location where I didn't know anyone.)
-the vehicle is used mainly on the street as a daily driver with very limited drag racing use.
-Will be autocrossed
-Will be used to race on the street fom stop light to stop light.
-92 octane or less!
-real street engines are driven below 3000 rpm (almost all the time.) Stock TPI system dictates that it won't be revved over 5500 and will stop making power at 4800-5000rpm.

The IROC is a fairly heavy car (3300-3500lbs) and the gearing? What is the gearing suited for? The T5 has a limit of about 300 ft. lbs of torque. What am I shooting for then? 0-100 in less than 5 seconds would be acceptable. If it gives out at the top end at the end of the quarter mile...meh. On a street race, you never really get to go 1/4 mile anyway before the cops pull you over. Maybe 1/8th of a mile. Besides, if you look at some of the newer competition out there, most new performance vehicles are doing 0-60 in 5.5seconds or less and quarter mile times in the low 14's or high 13's.

The cheapest way to increase performance on the LB9-Increase flow to the engine via:
1. 1.6 rockers on the stock heads to increase lift on stock cam
2. headers. 1 3/4 is probably as big as you want to go on a 305.
(That should cost you about $600 and you should get an extra 20HP right there-to 240HP without hitting the limit on the T5W.C torque capacity and without doing anything more. See below for more explanations and then it can start to get expensive.)
3. The MAF will take care of compensation for fuel and lift on cam to about this point. Then you need to increase fuel pressure to get the maximum out of your 19lb. injectors (anywhere from 250-270HP.). This is where your adjustable fuel pressure regulator comes in.

(In total that should cost about $9,00-1,200 for parts-you supply the labour) and get you into the LB9 limit of 240HP on stock stuff with stock injectors and no other mods. You should expect about a 15.00 run from 15.5's stock (an ideal car in a perfect world would run 14.05 with no drivetrain loss and no traction problems with this setup). You may or may not have to reprogram your computer at this point, but the MAF system should take care of compensating right now.

Then get suspension to hook with tires. Tubular control arms, poly suspension bushings, torque arm etc. etc. (I just spent about $2,000 on suspension and rebuilding the front end with Moog stuff and am still missing the torque arm.) But that should help you launch out and will help you corner if you do the front suspension work too.

Unfortunately, with the LB9's, if you want 325HP, which is about the limit on all Motor TPI (yeah-I can hear it now, most of you guys did it with NOS, another power adder, or no TPI-ie. Carb and spinning the motor to 6000+ on a 305) you have to stuff as much torque between where the TPI is strong, 2000-4000. You'll need heads that flow very good in that range like Vortec L31 truck heads, a cam that works in that range-pick one from any brand, or a smaller cam than the one used in this article http://www.popularhotrodding.com/eng...cks/index.html because you won't be spinning your motor up to 6500 on a TPI-the manifold and runners just choke everything up to 5000rpm. And most importantly, you'll need headers-big headers. They used 1 3/4. An open exhaust would make about 400ft. lbs of torque @3000 on a 305 TPI according to desktop dyno. But then, you run into the T5 issue again. And you run into the injector sizing issue and the related computer reprograming issue here as well and quite possibly you'll need a bigger 52mm throttle body here as your 48mm throttle body will quit at above 325HP. And with the T-5 issue, you'll require a T-5 with stronger gears and synchros or a T56 or aftermarket transmission. And Cam and Springs and on and on it goes...

Unfortunately, the more power you make means the more weaknesses you have to cure in the design of the car, which in turn means you need more time, money, and know how.

okfoz

Nels,
THis is VERY interesting... I appreciate the work and effort you put into this...

Welcome to the boards...

JOhn

Guest

Nice theory, but its far from factual. The intake base is the biggest problem to deal with. The factory TB is good to at least 400HP NA.

That is only if:
The assumed BSFC is correct.
You are only running 80% duty cycle (nobody does).

The injector flowrate is at 43.5psi, not 36.

Do you mean on any engine or just a 305? I'm certain you're wrong though even if you're referring to only 305's.

Nelz

You have the right to disagree with me, becaues there's always stuff I don't know enough of. However you don't provide a good explanation on your post of why I'm wrong.


I would agree with you in regards to the intake base, Ray T. Bohacz flowed the intake manifold base in Hot Rod a few years ago and came out to 222.45cfm. With the stock intake runners, it flowed about 198.72cfm.

As for the throttle body itself...check out this link:


http://www.revtronix.com/techinfo/calculators/throttlebody.php

The stock 48mm throttle body will stop at about 313HP - Naturally asperated.

According to the Chevy TPI Fuel Injection Swapper guide, you would need a 52mm throttle body that flowed 750cfm to get around 400HP.

Well, it's just a math formula and the recommended is 80% duty cycle. For more information on injection sizes and supported HP with different fuel pressure rates, I would visit:
http://www.hobracing.com/tech/normalisation.asp

-The only true way to know what you're flowing is to test your fuel pressure
regulator. According to the TPI Swapper guide, the 305's used 19lb. injectors at 36psi and the 350's deliver 22lbs/hr at 43.5psi. But again, the only real way to know is to test your stock fuel pressure regulator and find out.


If you read that paragraph from the beginning, I was speaking of a 305 LB9 (and meant the limits of the stock stuff and how to reach those limits) with a naturally aspirated motor-no blower, nos, turbo. The reason I came to this conclusion is because the MAF becomes a restriction at 325HP, the heads limit you to about 300-325HP unported, the TPI runners and throttle body limit you to this much, the injectors you'll have to replace, and the TPI system limits how high you can rev, so you're not going to see 400HP at 5500-6500 RPM with a TPI 305. You are stuck at under 5000-5500 RPM. I'm not saying that you can't go higher, but realistically, to get the stock TPI LB9 to reach it's limit in terms of air flow capacity, you've got a lot of work.

The best Chevy 305 buildups I've ever seen where here, and they all did it with Carb or throttle body. Not TPI. As a TPI LB9owner, I have to take into account the weaknesses and strengths of the TPI system. I'm not tearing this engine apart, the machining costs are not worth it.



http://www.chevyhiperformance.com/tech/engines_drivetrain complete_builds/0706ch_small_block_bolt_ons/index.html



http://www.goingfaster.com/spo/carcraft325hp305.html



http://www.popularhotrodding.com/enginemasters/articles/chevrolet/0667_phrs_305_chevy_engine_blocks/index.html



http://www.hioutput.com/tech/400hp/400hp.html

What I've learned in life is...set realistic expectations based on hard data
and facts and reach those limits. If you miss or exceed those limits, obviously you missed something in your original assumptions. This is my humble opinion of where the limits are on a MAF equipped LB9 f-body and the cheapest way to make it go fast without tearing the motor apart and
rebuilding the bottom end and dealing with the limits of the T5-because you will break it. (Otherwise, I would dump in a 350 with Lingenfelter stuff and a T56 ) And if you think I'm wrong, don't just say I'm wrong without adding a reason to it-that's just useless. This isn't a flamer post. It's a post about how to make the car fast enough to run with the new stuff out there
without resorting to taking the easy way out-Add a 350cu. in or bigger motor aor some other power adder) and strengthen the driveline for it. At the same time remembering you can buy newer cars like a 2008 Cobalt SS that will run 13's in under 25K.

Guest

Ok, if I use the standard data points and get it to 313HP NA, its only flowing 230 cfm @ 1.6kpa according to that calculator. Its pretty well known the stock TB flows in the 600+ range at 1.5kpa. Doesn't give me any faith in that calculator at all.
https://www.thirdgen.org/forums/tpi/...-injector.html
https://www.thirdgen.org/forums/tpi/...er-better.html
https://www.thirdgen.org/forums/tpi/145520-airflow.html
http://dtcc.cz28.com/flow/index.htm

Its well known the stock 305 injectors flow 19#/hr at 43.5psi. I'm not going to search this and post 1,000 results, I will let you do that. Look up rich at cruizin and see what results you get. This link also has proof tested in a lab.
http://dtcc.cz28.com/flow/index.htm
Additionally, the fuel pressure regulators are the same 305 and 350. If you have a TPI and a fuel pressure gauge, you can disconnect your FPR vacuum line and verify it for yourself.

Its easy enough to make well over 400 at the crank with a MAF. Been there, done that. I've seen the 300, 325, and 350 numbers thrown around and I know many people who went way past that on a stock MAF.

I dont think so. 331 at the wheels through stock runners. 415ish at the crank.
https://www.thirdgen.org/forums/tpi/...o-results.html

Depends on your definition of work. Stock runners, ported Edelbrock base, stock plenum except EGR walls removed, 58mm TB (that I can assure you added nothing to the power curve, wasted money) and the best pass at the track was with a 6800RPM limiter in the MSD box. Its a 350, but who cares. A 305 would do that easy, and would want more built the same. The only thing a TPI with stock runner length does fairly consistently is drop off at somewhere between 4800RPM (stock) and 5400 (modified). If you were to siamese the base (an extremely simple way to eliminate the TPI RPM wall from the equation on a 305), the engine itself will become your RPM limiter. Just keep in mind RPM=Ruins Peoples Motors so if you venture into the higher RPM realm, build accordingly. I would not advise over 6k on factory rods with factory bolts.

You havent searched much then, or you want something really out of the ordinary. There's a few I can think of posted here that were in the 12's NA. Then you have a boosted car running 10's, and mine is somewhere mid 12's with a stock motor and lots of extra air pressure. Look up Tim Burgess for a good NA combo. Willie has a nice boosted setup (I'm sure it'd run quite well NA from his past NA results) and you might want to look up Preston Smith. There's also Fast355 that mostly built TBI stuff but has gotten some good results on his TPI swap as well.

The same basic power modifications used for the past 40 years work fine on TPI engines, the main difference being the restriction inherent in the TPI itself. Most of the problem in raw power numbers is the base itself, but on a 305 its a lot less of an issue than it would be on a 350 or bigger. Still, its the first thing to look at. The runners, TB, and injectors are going to get you well past the 300 mark and you should be able to get 400 at the crank before those items start becoming an issue. I'd be a lot more concerned with the factory heads and especially cam, and getting the base to flow well enough to support that kind of HP.

As far as the right/wrong thing, posting up links to internet sites and books with questionable data or information isnt supporting any claims. There are multiple users here that have actually done the work and posted up actual real world results. If you're quoting magazine articles and a guy whos never tried anything he writes novels about, you havent read anything worthwhile yet.

This post should not be here, it really should be on the TPI board.

Nelz

350 build up's don't apply that well to 305's becaues the 350's breath better with a bigger bore. We agree that the TPI is the restriction from 4800rpm-5400rpm and 6000rpm is the limit on stock bottom end. I would agree on one of your engine TPI posts, work on headers, intake base, heads and cam in that order. The 350 has a different air capacity volume and has more cubes. You're right, the 305 will want more air, fuel and compression to get the same and on a stock TPI, it can't because you're right, a 305 doesn't have the RPM to do it.

The proof is on this thread regarding the LB9's.

https://www.thirdgen.org/forums/tpi/...tpi-305-a.html

Most LB9's on NA run high 14's to 15's. I see a turbo on Preston's Iroc. And again, it's bored out to 4". (350.) They talked about another 305 stroked to 335cu. in. mw66nova's car is fast for a 305, but it's carbed and spins up to 6500. Another guy is using twin turbos. Many are on NOS. I completely agree with Orr89RocZ, "theres lots to be had but no one really builds 305s. its cheaper and faster to do a 350."

You're moving beyond the main point and using examples of TPI engines that are bigger than 305 or using power adders.

Why waste that much money on an LB9. freestylzz had the basic bolt on's and only ran 14.9's without opening up the block.

David 91RS/Z28's car used L98 corvette heads, cam and gears!

chikn305's car deleted the stock TPI system for a TPIS big mouth base with larger runners to spin his 305 LB9 higher, gears and nitrous.

TunedPort 335's car had a 335cu. in. He paid to build up and strock a 305 bottom end. (It's interesting, but you could have bought a 350.)

GregWestphal's car seems to be what you would expect with a TPI with headers and regular bolt on's.

They were all very interesting LB9 build ups. But for many people to get to where they wanted (sub 14's) they needed power adders-i.e NOS, turbo, more cubes-335cu. in, or non stock TPI's to spin the motor higher-above 5000rpm.

This shouldn't be in the TPI section because it was originally meant to look at the entire weakness of the vehicle and where the limits are in relationship to the LB9. Driveline problems in relation to the stock T-5 and rear end in relation to the LB9. And not to expect much from your LB9 because it's hit those limits stock and on upgrading the LB9 to match the limits of the driveline, you'll require further cash, time and know how.

Pyroviking

iTrader: (4)

Very interesting and thought provoking conversation, guys. I'm looking forward to following this thread.

Cheers!

89ROC-Z

iTrader: (7)

Subscribed.
This is very intersting as its the same setup that i have.

Fast355

iTrader: (2)

The NA TPI 310 (.030" over 305) in my Van has produced this time slip. With 3.08 gears and only a 2,600 rpm stall converter.

jwscab

just a clarification, on the injector size and fuel pressure. I believe the TPI swappers guide was giving advice based on the initial year TPI 305(85'). This system did use a lower system pressure. 86 and up went to 43psi.

Guest

Preston's car has always been a 305. If you think its a 350, you havent read about it. It was previously a 3.736 bore with a supercharger and ran 10's. I'll bet if you removed that, his car would still run mid 12's NA, much the same as Tim Burgess' car. If you want something that works, follow them.

Nelz

Ok, so Preston's car is still a 305. From that post it mentioned a 4" bore. 4" bore x 3.48" stroke = 350. Ok, say it's not a 4" bore but a stock 3.736 stroke. Turbo is still one way to go on an LB9...but it's still a power adder.

Tim had a very impressive setup. Made the LB9 spin up a little higher and got into high 12's, low 13's with some gearing help. Tim had a very impressive setup. But I'm not willing to spend the type of cash Tim did. Reading about Tim's setup, he maxed out the capabilities of a stock shortblock LB9 and probably replaced the stock T5 and rear end for a reason-all good ones.

To me, I'm not willing to go to the extent he did. The car itself-with the transmission and rear end limits, well....that's as far as I want to take an LB9 becaues then it cost more $$$$ to buy a new tranmission, or I can just buy the g force gear kit and spend a weekend to re and re the T-5 to handle 500# of tq for $500, and then the rear end becomes the bottleneck in strength at 400#TQ.

My whole thought was to not touch the bottom end, because if I did and have to pull the motor out, then it would just make more sense to drop in another 45 cubes or more. If I had to machine a 305, the labour costs are the same to machine any other block-so add cubes!!!!

You're right, I could NOS it with a 150hp shot or turbo it like Preston's...but there's just something about NA engines that get me.

From a cost benefit point of view, on an LB9...limits are:
Stock Prom
Stock injectors, when you bump up fuel pressure, after a certain point you need to burn another Prom. Under a certain limit, the MAF and stock prom will compensate.

Do i really want to spend another $300+ on prom burning and a week rewriting fuel table values? Not in particular, but I will if I have to.

Ok, if that's out of the equation, what else can I do to make the car,faster what can I expect, where can I be disappointed and can I live with it?

Hmmm....

Let's see. Strengths of car= engine good from 2000-4000rpm. No HP after 5000rpm. Injector and stock Prom limits of 250-280HP. T-5 breaks around 300#Tq. Rear end breaks around 400#TQ.

250HP on a 3300lb car good for 14-15s 1/4 mile pass.

Stock LB9 has 220HP and 300l#TQ.

What can I do without opening up the bottom end and buying a new PROM?

-1-5/8-1-3/4 headers $200-900 for a 20-40HP gain
-Heads-port stock, or buy better heads $100-1000 for a 20-50HP gain
-Add lift. 1.6 rocker for $100-200 for 10HP or new roller lifter for $300+ and springs, retainers, keepers for another $150 for 20-40HP gain.
-Adj. Fuel pressure regulator + gaskets = $75-100 for 5-10HP
-Roller Cam $300 add $150-200 for springs and keepers

MODs to increase airflow at upper range
-Hi Flow runners-$300 to gain another 300RPM
-Hi Flow TPI base $400 or spend a week grinding for 2-3HP according to TPIS...not worth it.
-Air Foil- 6HP at 5000rpm according to TPIS. Cost=$50. Potentially worth it.

Mods to avoid
-New Prom or Computer $300-600 (TPIS is charging that much now a days)
-8 New Injectors $200-300

What does the engine really need?
Airflow requirements of engine.

Cubic feet = CID/1728
Cubic feet x RPM/2 = Ideal CFM
Ideal CFM x .8 = actual CFM of engine.

So... 305/1728 = 0.1765 x 5200 RPM (max on a TPI car)/2 = 459 cfm in an ideal situation. Realisticly 459 x .80 = 367 cfm is all the air a 305 will cycle through at 5000rpm.

So the intake side of the TPI is near good enough.

Why?
According to TPIS:
stock air filter lid and clearner flows 648 cfm.
MAF flows 529 cfm stock and 711 cfm with screens removed
48mm throttle body flows around 630cfm.

Where does that leave us stuck?
Intake base flows about 211 cfm.
Heads stock 14102187 or 14101081:
https://www.thirdgen.org/forums/tpi/...formation.html
Intake flow about 158-181 cc's stock @ .400
Exhaust on the exhaust valve flows 107-133cfm on exhaust stock @.400

Ok, heads a restriction, exhaust a restriction, intake base and runners a restriction-but not as bad as heads and headers. This is where I'm dumping my money.

Port or buy new heads $100-1000 (Cartridge rolls, carbide cutter and grinder on low end of this budget)
Headers $200-1000
Cam + Kit $300-600
1.6 roller rockers if i just want more lift from stock peanut cam $300 because this is the lift I would get with 1.6 on my stock cam
https://www.thirdgen.org/mods3

240-280HP, no replacing my T-5 or rear end so good enough. Plug it into an E.T calculator and what do I get? 14-15s. run on a relatively stock LB9 TPI engine without pulling out my LB9 from the engine bay or re-burning the prom. $ outlay $300-2,600 (assuming just porting the heads and 1.6 roller rockers on the low end). Am I disappointed that I didn't go into 13's? No, because I expected to go high 14's.

Did I waste money on stuff that won't give me the greatest hp/$ advantage? No.

If I want to go into 13's, ok, fine MadMax. NOS me. Chip the computer for it, spend $600-1000 on the kit and computer and the whole thing for a 150hp shot of laughing gas. 220+150=370HP, good enough for 13's on a 3300lb car.

okfoz

IIRC TRAXION had the killer setup, Normally Asperated, 30Mpg, and 12's in the quarter with a stock bottom end? correct me if I am wrong...

John

Azrael91966669

my 1.6 roller rockers where worth 16 rwhp and 12 tq

my TES headers that i picked up for 75 bucks where worth 14 hp and 20 tq along with a flowmaster muffler

but i had the stock Tbi exhaust before that

rear end gear swap real seat of the pants differance one biggest increases for cost
i went from 2.73 to 3.23 i did that when my car was still tbi went from running 16.9 to 16.1 just from gears still slow but it made a huge differance when driving that tbi really needed gears

adding tpi with stock tbi exhaust it dropped down to 15.6 not bad for just a speed density tpi swap

headers got me down to 15.4 with almost no traction off the line
roller rockers said i had more hp on the dyno but ran 15.4 still but in warmer weather so maybe thats why



gm should have used a differant engine code for peanut cammed lb9s vs the l98 cammed ones they are to completely differant animals .
an 90-92 tpi 305 seems to be a much better motor because of the cam

i just swapped one in after my lo3 spun a rod bearing and it feels alot more powerful

if your gonna do bolt ons for a 305 lb9 do like i did
i spent 100 bucks on 1.6 full roller rockers
100 on a used posi with 3.23 gears on it
75 on a set of used edelbrock Tes headers because apperently nobody likes them they do there job made the car faster and sound alot better cant ask for anything more

i may have only spent 275 bucks for the mods but they made real differance

if you spend your money wisly you can compete with far newer cars
there are a lot of cheap ways to fix weaknesses in these cars

hellz_wings

iTrader: (2)

So.. Correct me if I'm wrong but the stock 19lbs injectors on a 305 limit the hp to 259?? Would that mean that installing bigger injectors and burning a new prom would fix that problem??? Also maybe replacing the stock fuel pump with a bigger one.. 190lph or 255lph.. Which one is better they are about the same price... Might as well get the bigger one no? To me this seems like the biggest HP restriction so far.. the fuel!

TA

iTrader: (1)

This is the problem with the TPI cars, there is no one or two "magic bullets" that you can change and suddenly gain a ton of power, the whole system is tuned for bottom-end power. To get high-end power requires components that are a mismatch for the stock stuff designed for low-RPM use (exception is good heads) so changing to high-perf components piecemeal often will produce little performance gains until you have all the other components in place to re-tune the powerband of the entire system. Once that is done properly, very good results can be had, but the pieces and parts method just never seems to bring the desired results.

TA

hellz_wings

iTrader: (2)

Hm ok but I have done almost every mod to the TPI that I can think of in terms of air restriction... Also my ignition components are all new and performant... now it all comes to re-doing the fuel system and tuning the chiip (which i have all the stuff to do from moates.) . My question is that should I buy new 19lbs injectors or should I get a larger# injector in order to make more horsepower? My sig has all my info on mods..

Nelz

I wouldn't bother buying "new" 19lb injectors. For fun, because you may have to step up the injectors anyway, I would just tune the car for now with the 19# injectors you already have and drive it....your sig says you have ported 416 heads and cam. Since you can tune the computer, just tune it and up the fuel pressure a bit.

The injectors just become a restriction as it is not delivering enough fuel and the stock computer becomes a restriction because it cannot compensate anymore after a certain amount of fuel pressure. See this link http://www.hobracing.com/tech/normalisation.asp.

Although the 19# injectors with a higher fuel pressure (and this site, they seem to assume a .50 BSFC, so it's a worse case scenario-you're tuning your car right?) will atomize the fuel better according to TPIS, you're going to run into it's limit depending on how efficient the engine is. Lets say you actually bump it to 50psi. Hobs says you'll get a fuel flow of 20.3. 20.3(8x.8)/.44 = 295hp assuming you can tune and get the car to run at .44 bsfc. Bump up to 55psi and you get 21.2(8x.8)/.44=308.36hp. Bump it up to 60psi (this is probably streching it) and you get 22.2(8x.8)/.44=323hp. If the engine is more efficient than that well...355hp is kinda at the limit then-but it would have to be so efficient that it will pull a .40 bsfc #. Since the stock computer is no longer the limit and you're tuning the car, you may be able to get away with bumping up the fuel pressure and just tuning the crap out of the car and saving yourself the cost of new injectors.

Besides...if you lock up the injectors, you can step up your injectors then. I'm just concerned that if you mis-tune it, you'll lean out the engine enough to blow it up....always the problem so be careful when you tune it.

Alain2

I just want to confim that the stock fuel pressure is NOT 36 PSI.

I just installed a AutoMeter gauge on my stock 1991 305 TPI and I got 45 PSI STOCK.

I trust Autometer, but I'm wondering if I have a 1.5 PSI error? Or maybe my stock FPR is off 1.5 PSI?

89ROC-Z

iTrader: (7)

Dumb question, but how do you install the gauge and run the lines? Does the line just screw on the fuel rails?

Fast355

iTrader: (2)

I agree with you... The stock regulator on my 1986 305 TPI fuel rail in my Van runs at 46 PSI. The diaphram has been replaced but it is otherwise untouched.

Alain2

It is pluged on the stock fitting of the fuel rail.

89ROC-Z

iTrader: (7)

^^Thanks man! I'll deffinatly have to get a pillar pod and do some gauges.

hellz_wings

iTrader: (2)

Going back to my old question...

So the 19lbs injectors can technically go to 355hp? That's great... It's 101hp up from where I am at now... I am sure there will be other restrictions before I get that far anyway.

So at what pressure is the max output on a TPI? How would I go about changing the pressure (I have a Billet AFPR installed)... My mechanic actually lowered the fuel pressure than what it was before and said it made more power on the dyno. I found that odd since everyone seems to be making more power by adding fuel pressure...

In the meantime I will tune the car by adding more fuel and timing as much as I can without making it knock and maintaining INT's and BLM's as close to 128 as possible.

Thanks,
-Marc

83 Crossfire TA

iTrader: (2)

Old thread but I ran across it and I feel that there are a few things that need to be added/clarified:

- Most injectors are rated at 3bar (43.5psig), for example, ford 19's are rated at 3bar, but are run at a lower pressure in the car, that means that they'll flow 19lb/hr at 43.5psig.
- GM port regulators are not adjustable and are designed to maintain 42-45psig at the rails... a few lbs here and there doesn't make enough of a difference for the ECM not to figure it out and adjust accordingly, typically gasoline quality makes a bigger difference.
- Most 80's GM FI setups (definitely TPI and TBI) run fastest (that doesn't mean that they don't run rich in part of the fuel curve like this) with a little more than stock fuel pressure. I've found that most TPI cars run fastest with 52-54psig, and TBI at 13-15psig fuel pressure (of course, the same gains could be had at any fuel pressure setting and a chip burned to add fuel where it needs it)
- Stock TPI intakes have tuned length runners which have a tuning effect at between 3000-3600rpm. The don't really work below that or above that (that is where the harmonic peak is, above and below that is a harmonic trough that it actually makes less power than it would if there was no harmonic tuning, meaning almost any intake will make more power below 3000rpm). The stock parts tend to run out of breath at around 4600-5000rpm on a 350, and 5000-5500rpm on a 305 (the reason that this tends to be a little above what you usually see in these cars is that the exhaust also tends to limit their top end).
- LB9+5 speed (non peanut cam) will run mid/low 13's with a good driver with a decent cold air intake, headers, exhaust, mid/high 3 series gears and sticky tires. If you have that combination and can't break into the 13's, you're doing something wrong, your car is too heavy (above say the mid 3xxx range) something is broken and/or needs tuning or you need some practice driving.
- Preston's turbo car's engine has about as much in common with a factory 305 as any other heavily worked aftermarket small block. It was not a 305 block, it was a 4.000" bore block overbored .025" (4.025" bore as opposed to the 305's 3.736" bore, you can't get there from here), custom pistons, 6" rods (factory rods are 5.7" for most small blocks, 5.6" for factory 400small blocks), tfs heads... I don't believe that there are any rotating assembly/bottom end parts that would even interchange with with a 305 with the exception of some bolts.

83 Crossfire TA

iTrader: (2)

Oh, and to answer the last question... yes, on a well tuned, well matched combination 19pph injectors are big enough to feed 355hp, but if everything isn't perfectly matched you'll have issues unless you bump the fuel pressure some.

hellz_wings

iTrader: (2)

I am in the process of tuning my car ... I've done tons of runs out of it... 14.2 was the last one i got on my 305, i have everything i need to tune it, i've run datalogs, i just need the time now. Hopefully i'll get on that soon. I may need a new throttle body because mine lets air in at idle, not a big deal, but if i'm tuning for precision, all these parts have to be 100% working. At first i'm going to tune the AE first and then work my way around the RPM tables. As for fuel, the whole point of tuning is to see how much fuel I can add, while adding spark, to gain as much power as possible WITHOUT detonating/pinging, right?

83 Crossfire TA

iTrader: (2)

Maximum advance without pinging does not always equal maximum power...

hellz_wings

iTrader: (2)

So I'm probably going to stick with the 19lbs injectors for now, and tune it with this until they blow up or they reach their maximum potential, either way, i gotta start somewhere!
Thanks!

Nelz

Um....let's not get hasty here! You just rebuilt that thing a few years ago based on your webpage ---2years ago??? Do us all a favor and DON'T blow up your motor for our entertainment YOU HAVE BEEN WARNED!

If you're still running the original Lingenfelter Accel base (and not the edelbrock outsourced one-does your base actually have ACCEL cast into it?), with the ASM LTR and 52mm TB, you might be able to rev that thing up to 6000rpm with a set of beehive springs. (You're running ported 041's?) I just don't know what your cam specs are.

IF you are planning to tune it, do us a favor and buy the dyno time and WB02 and don't lean out your motor until it blows up! (It sucks every time that happens!...and although some people may find it amusing, you've got a pretty nice set up.) And low 14's are pretty alright on a 305 car.

Nice ride! It would be a shame to have to rebuild that thing so soon!

TxTtopZ

Speaking of ported 416's, I have just got a quote of $700.00 to get the heads reworked (ports ,bowls ,studs, valves) how much better is the 305 with this done? Is it worth it? I am also looking into vortec heads but cannot find any post that actually has a milled 062 or 906 head on a 305.

Nelz

Don't bother. Go with Vortecs. Especially with TPI. See this article.

http://www.popularhotrodding.com/eng...cks/index.html

Scoggin Dickey has them ready made for .600 lift or the Edelbrock Aluminum versions (not the E-street if you're looking for .600 lift-the E-street) or EQ lightnings or I think even the Dart Platniums or RHS and Canfields are similar to Vortec in chamber shape. Or even get bare Vortecs and get the machine shop to machine them for beehive 26915/26918 springs. (talk to your machinist first, but you may still have to change valve guides to bronze, install screw in studs, machine valve guide boss down, enlarge push rod hole to 1.5", and still end up buying self aligning rail type rockers. Comp 1.6 magnums roller tip rockers work with 26915 beehives, but not the "new" improved 26918 beehives because open load on the "new" improved 26918 springs have open pressure of 367lbs where magnums only guarantee non-breakage at 350#. I still haven't heard back from Comp's e-mail tech support line on this in over 2 weeks)

hellz_wings

iTrader: (2)

When I bought the car, the guy I bought it from did all the engine work, but I don't know the cam specs and he doesn't have any of the information anymore, so I just know that it was an 86 block, I don't know what heads it had, but I did some research and I believe that they were the 416 heads, correct me if I'm wrong please. He said that the whole bottom end was done over (bored 0.030, forget internals, "oversized cam" was all i got with no specs, ported and polished heads, etc.). So I'm sure more was done to it but unless i dig in there, there's no way to find out what exactly was done, including the cam specs.

My intake manifold does indeed say Accel on it, it was very expensive too. I have AS&M longtube runners, and my throttle body is stock with an airfoil but i'm getting a rebuilt 52mm one (but that's just cuz mine has a worn out shaft, so might as well get 52mm). I have dyno'd it before and it make power up to 4800RPM but that was with some check engine codes so i'll do it again soon to see now that everything is running properly.

My last run I got 14.2 but that was bald tires, I'm positive i will get into the 13's with the new Firehawk Indy 500 Wide Oval tires I just put on, they grip like a ****.

I have thought of getting a WB02 but I didn't think I needed it to tune.. I know that you can tell you air/fuel ratio better with a WB02 than the ECM, but I thought just by getting readings from the ECM it would be enough (like getting BLMs and INTs at 128, etc.)?

The biggest upgrade of all though, was going from 2.73 open to 3.73 posi, all these bolt on upgrades just gave it a bit of oomph every time, which added up to 271 fwhp.

TxTtopZ

Yeah, thats kind of where I was going with that. I am looking for an actual user somewhere other than a magazine. I think EQ vortecs are the best bang for the buck head, period. After careful consideration about engine swaps, pro and cons and expenses I have come to the realization that I am going to have to use the 305 for a while. I am not that bummed because I am just looking for high 13's at this point. Shouldnt be too hard, especially with the EQ vortecs, and an XE256 or XFI260 H13 cam.

TxTtopZ

I think my car came with 3.23 gears stock. Its an 85 Z28 with an LB9 and I know its limited slip for a fact (sorry Duval medical center) lol... and I have those same tires on my car, the Indy 500 Firehawk's..new. Yes! they grip pretty well! They put out some decent smoke too ;

Nelz

1. If you really want to know, take off the valve cover and find the casting number.
2. As for figuring out the cam, I remember John Lingenfelter wrote a section on how to figure out Duration and Lift of an unknown cam using a degreeing kit without tearing the motor down. (It's in his John Lingenfelter on modifying SBC's book. he mentions it on pg. 100 and details it in the blueprinting section.) http://www.ls1tech.com/forums/genera...known-cam.html has a similar method.
3. You've got a lopey idle so it sounds like it's got a fair bit of overlap, but it's hard to tell until you determine the cam.
4. Unfortunately, if someone else rebuilt it, you never really know what you have. It may NOT have a forged bottom end and you would never know without doing a teardown yourself to find out. (I remember there was something specifically different about the 305 crank that caused it not to interchange with a 350 without a lot of balancing.) But I've also never heard of someone making a specific forged 305 crank-I have heard about the powerhouse 335 305 stroker kit though!
5. You need a WB02 to tune A/F. Go to the D.I.Y tuning section and reread everything there. It makes it a lot easier.

TxTtopZ

Everything they make for a 350, they make for a 305. Forged anything and everything. Scat makes a crank for sure, JE makes pistons for sure, if you look at the sprints it a whole nother world for 305's. I hate telling people to do a search but... Also is the 334 crank forged? I thought it was cast?

hellz_wings

iTrader: (2)

I've heard of the 305 stroker build too... it's a cool idea, but i haven't seen dyno numbers to show how much power it'll actually make.

Which side of the head will have the casting number and where would it be? I definitely want to find this this out.

Where would I find this degreeing kit? I don't think this is a standard practice so I imagine it must be hard to find one.

The old owner said the cam was a GM cam. But then again, everything I know about the internals is based on what he 'said' or wrote in the ad.

Ok, so definitely getting a WB02 since I am going to dive into serious tuning very soon.. I'll re-read the DIY PROM board stuff and go from there.. I did spend almost 500$ CAD on tuning stuff so I don't want that money to go to waste!

TxTtopZ

The heads are the exact same, so under the easiest valve cover (driver side). The pointer points to the tape on the balancer, this is basically like finding TDC when installing a cam. I would get timing tape if your balancer has no marks. I know of one member who has a 334 and I think he gained 20HP or so but dont quote me on that.

83 Crossfire TA

iTrader: (2)

WOA!!! Don't discourage him like that...

But if you're going to do it make sure it's dramatic and have a video camera running

hellz_wings

iTrader: (2)

lmao i'll try NOT to go that far haha.. and there's about 5000 miles on the engine rebuild now, it runs like a champ! I'm willing to take a few risks but i usually take my time with these things so if i go slow i think i should be fine!

1bad91Z

iTrader: (1)

Just wanted to add my ...

GM uses that same stock 48mm TPI throttle body on their Ram-Jet 502 BBC crate motors that make 500 plus HP at the flywheel...

NY3RDGEN

You sure about that. My friend just got one in his truck. ( RJ 502) and i was looking at it last weekend. and the throttle body looked huge.

And since theres a bunch of 305 and 350 vs 305 guys here now. Let me ask. How fast do you think my car can go if properly dyno tuned?
BTW, I have the 2032 Compucam with 1.6rr's rest in sig ??

hellz_wings

iTrader: (2)

I heard stock throttle bodies go up to a pretty high HP number (more than enough for a NA 305 motor no matter what upgrades or bolt ons).. But after 24 years of pressing the throttle, the shaft becomes loose and lets air in causing minor unstable idle at times and the only replacements are 52mm or higher.. Unless they make replacement 48mm shafts for under 150$? Doubt it tho.. Gm one is probly 450$ lol.. And that's if they still sell em'!

TxTtopZ

Its hard to say. Most 305's with a power adder get in the low 12's. I would really like to see just 1 real 305 get into the 11's before the owner decides to go to the "bigger brother". I am sure StreetLethal is there with a turbo and You have that chance i'd say.

Oh and I found going to vortec heads is not cost effective and actually goes against the original outline of this post. To get the heads new, that are already machined for higher lift, or to get some cheap, machine them and buy the valvetrain parts is about $650.00, (these are cheap side quotes) plus the lower intake to match is another $400.00. It seems the real answer based on others' accomplishments is to do some porting work myself on the 416' since I already have an air set up.

hellz_wings

iTrader: (2)

Which head casting came on the 86 iroc 305 tpi's?

TxTtopZ

The same ones i have, which is the 416. If you have perimeter style bolting on the valve covers, it's got 416's. If its got center style, its the 081's.

hellz_wings

iTrader: (2)

ahhh. i have center bolt valve covers, so it must 081's then... it's the 'original engine' but just modified completely.. cool! thnx

TxTtopZ

From what I have gathered, the 081's flow a little better than the 416's. Some say they are the same, save for the bolting style but if you look at some sprint car websites where the 416's are popular, they all seem to say the 416's flow a little less. This seems to be backed by sprint car machine shops.

hellz_wings

iTrader: (2)

ah.. cool then, i guess.. Either way I know my heads were ported/polished and rebuilt, along with the engine, about 8000 miles ago.. So they must flow pretty well!