musclecar70sfan

iTrader: (1)

Hey guys, well I guess it's an inferiority complex kicking in or something but I can't stand seeing my 91 Trans Am LB9 getting whooped so easily by a lot of things out there. So I wanna save up cash for an L98 swap for the wintertime; maybe sooner if I get lucky. Reason I wanna stay TPI over LT1/LS1 or anything else is because of the easier plug-and-play plus factory looks. If I'm not wrong, all a 350 requires is a different knock sensor, bigger fuel injectors, a computer flash, and maybe a few other minor things. I've seen a ton of SBC 4 bolt 350s and even actual L98s for sale nearby that aren't crazy expensive (I saw an L98 PLUS trans for sale for $1000 OBO out of a wrecked C4). So I know that when it comes to dumping money into a 305 car, a 350 swap is the way to go. For starters, what would it take to reach a 0-60 in the mid-high 5s (I'm thinking that might equal around 13s in the 1/4?) with a naturally aspirated L98? What kind of rwhp/tq would those numbers require with lets say highway-friendly gears (maybe 3.23s)? Thanks!

vetteoz

iTrader: (13)

A TPI is only a TPI because of the intake.Once the intake is gone it is just a regular SBC.
Buy the best 350 you can and put a HSR on it. Still PnP with TPI wiring
You will be miles ahead

Rolling Thunder

Im going to take a guess and just figure your car weighs about 3500 lbs with a driver. This means to get a car down into the 13s it would take around 300 hp at the wheels. This is pretty doable with a TPI intake on a 350. As far as what it would take to get 300RWHP out of a 350 TPI you pretty much need to do all the standard stuff you would to any SBC cam exhaust the heads may be good enough depending on what heads you end up with and even though you want to keep the TPI set up you should upgrade the base and runners. I think the gears you picked would be fine for TPI as TPI generates a lot of low end torque so it doesn't benefit from steeper gears like other cars do. The other key to this equation is traction. A well worked 350 TPI can generate around 500 foot pounds of torque which can help provide great 0-60 times but only if you can put it to the ground. All and all I think your goals are pretty reasonable just have to do all the standard stuff you would with any car.

bbtaz97

iTrader: (3)

ya you can def get a 13 out of a 350tpi motor with the right setup for sure..

even with the stock cam and heads ill venture to say. headers and exhaust are a must along with a good tranny and converter ( i have 2400 rpm) and rear gears ( i have 342) .. the stock intake in crap unless its worked over and runners are crap . those will majorly limit your upper rpm power. it will also help if you have some suspension work to get the power to the ground . also don't discount weight reduction as a helper to your quest for the 13's . good luck...

RED86Z28

TPI is fine but dont get hung up on the L98.

musclecar70sfan

iTrader: (1)

Yeah I wanna keep the under-hood appearance factory looking (for the most part) as well so I was thinking of getting either siamesed or larger diameter intake runners for the TPI. I meant to add... I'd like a car that is still practical to drive daily during warm months, since that's what I'm doing with my LB9 right now. How much money do you think I would have to sink into a stock L98 to achieve my goal? Maybe I can get away with $1,500 if I look in the right places? I wonder what a 383 conversion would require....

musclecar70sfan

iTrader: (1)

Oh I know... and HSR stands for Holley Super Ram right?



I'd be REALLY happy if I can put 300 hp down onto the asphalt... might take care of those annoying WRXs and possibly STIs assuming I can hook up lol.



Thanks! I don't wanna reduce too much weight since that will probably require pulling stuff that might come in handy considering that this car is my driver for the non-winter months. I already pulled the AC and I'm regretting that.

Rolling Thunder

Holley Stealth Ram actually.

Abubaca

iTrader: (3)

Before you do anything, sit down, take a deep breath and REALLY be honest with yourself about what you want. Speed? Fun? Driveability? Budget?

Right now, I have a stock TPI intake on my L98, with a ZZ4 cam, bolt ons, and a full exhaust. Full aftermarket suspension, and a T5. Lemme tell you that my car is downright FUN to drive!!!!!! ...but at the end of the quarter mile, quite honestly it's not really all that fast. When I had the Automatic and 2400 stall, I was faster than my buddies stock LB9/T5 car, but not by a huge margin, and his was actually MORE fun to drive, and got better mileage. In a straight out drag race I was faster, but who cares? Maybe you, I dunno, but I want to ENJOY the driving more than I want to be fast. ....and of all the mods I've done, easily the 3 best were the shocks and springs on the corners, then the 2400 stall, and then eventually, without out a doubt number one being the T5. None of which actually involved cubic inches or horsepower.

I also have another buddy with an automatic LT1 TA, with bolt ons and a supercharger. He's got more than a few kill stories to his name, but dear lord the car is boring to drive. The supercharger brings on power very smoothly. The small cam idles smoothly. The stock automatic shifts smoothly. UGH!!!! Borrrr-ing! ...but it'll smoke my car anyday!!!!!

If I were you, I'd look into a higher stall TC, or a manual swap. Maybe some shocks and springs, and maybe a deeper gear ratio. BUT of course, it's all up to you. The FIRST mods I made years ago were to the motor. In hindsight, they should've been last.

Stephen

iTrader: (12)

Just remember......

If you use a Corvette engine, you'll have to swap all your accessory mounts over/ The way the Corvette stuff is mounted, it won't fit in your F-body.


Some of the accessories themselves might be useable, but not the mounts/brackets themselves.

So it is very far from impossible, but possibly not as easy as you might have suspected either.

BigWhiteGTP

Get the L98, give it a full tune up, new cap, rotor, plugs and wires, maf relays, etc....the works.

Then, cone filter, bump timing up a couple degrees, good 1-3/4 headers, 2400+ stall, 3000 would be pretty good for future mods, trans go shift kit, governor recalibration to increase shift points a few hundred rpms higher, and Mickey Thompson ET street drag radials and BAM!!! Mid-low 13's

Stephen

iTrader: (12)

Cone filters might increase the amount of air someone can get, but also equals noting but incoming hot air. Hot air = less oxygen.

BigWhiteGTP

Increasing air flow period. The stock filter housing blows.

musclecar70sfan

iTrader: (1)

Definitely... and I might fab up a little heat shield to keep that air cooler.

Stephen

iTrader: (12)

More air does you no good, if it has less oxygen in it.

musclecar70sfan

iTrader: (1)

Yeah but I sure that a nice big cone will be better than the little 3 inch (if even that) opening in the stock housing. And I'll make a heat shield with some sheet metal or something. Anybody know the part number for a K&N cone that'll fit the stock air intake tube? I'd like to do this little mod with my LB9 right now actually.

Stephen

iTrader: (12)

Yes, the stock intake is on the restrictive side, but how is 1 3" inlet of cold condensed air (CAI) less restrictive that a 3" exhaust pipe of hot expanding gases?

Ditch the cone filter & build your own CAI out of PVC pipe, if you want it done as cheap as possible. As for the filter location in the last 2 pics.....Put a splash shield under it, if your car ever sees rain (this one doesn't).

BigWhiteGTP

?? A different size air filter in the same location as the stock one will do nothing to change air temperature. So a bigger cone in place of the crappy stock housing will increase airflow.

Back on subject co-founder.

Stephen

iTrader: (12)

Filter & air intakes directly relate to "350 TPI potential", so we are are still completely on subject.

I never said SQUAT about air temp & stock housings. Open filters get more hot air than stock intakes wit filters. That cannot be denied.

You are apparently completely misreading everything I have said. Extra hot, underhood air, lacking oxygen, will NOT do better than cold, more oxygen rich air. And that is an absolute FACT. Oxygen is what power, not merely volume.

You can increase the volume all you want. But if there isn't OXYGEN in it, so won't do you any good.

built91Z28

To test this, take an empty plastic bottles. The new real thin plastic bottles that water comes in work perfectly. During the hot part of the day, open the bottle and let it sit for a min. Now put the lid on and turn the AC on in the car. Put the bottle in front of the AC. It will only take about 20 seconds and you will see the bottle being sucked in on itself. This is because the cold air is much denser than the hot air. There is more oxygen per cubic foot than hot air. What the bottle thing will show you is how much more cool air you can fit in a given space than hot air.

musclecar70sfan

iTrader: (1)

Ok guys I appreciate the advice but let's not get this thread closed lol. I can see where both of you are coming from. The intake that Stephen is showing looks very cool.... I can even see a ram air possibility coming from that. But yes I'd have to build the splash shield since I drive my car a lot (put 700 miles on it in 8 days!).

Anyway, I was thinking that once I get my hands on an engine, I'd consider the Vortec heads since everyone seems to like them and they were available on some factory GM cars... and they appear to be cheap which will be crucial to this build assuming I pull it off. I know that they'd require a Vortec TPI manifold as well. Good choice?

And Abubaca, to answer your question, I'd love some of each! I want a car that is respectable in the 1/4, is capable of killing some mustangs and most r*cers (and some WRX's... Gawd those things **** me off), and that is still practical to drive daily. All of this hopefully without costing me an arm and a leg to build. I'm sure it'll be oodles of fun to drive... I actually already get a kick out of driving it with its stock LB9. But I have faith in the 350, and it doesn't seem like they need much to really scream. If I can put 300 hp down at the wheels... I'll be very happy. What's the amount of power lost from the crank through the rest of the drivetrain anyway? Is it something like 20%?

And a 383 stroker kit is sitting in the back of my mind... I've seen a forged set with rods, crank, and pistons that can handle 500 hp for about $600. I'm not looking for that power now but I figured it might create a solid foundation for something like forced induction farther down the road. Is that a good price?

RED86Z28

If things were that easy we would all be in the 12s.

Abubaca

iTrader: (3)

Musclecar- I wouldn't go the Vortec route if you plan in keeping the TPI. The edelbrock manifold is very restrictive compared to the "non" vortec aftermarket manifold. The head itself isn't bad, but it's not a great choice for the TPI crowd.

musclecar70sfan

iTrader: (1)

Oh I see, thanks for letting me know! Would it be worthwhile to put on the corvette L98 heads? Or can I do better?

ASE doc

Just a comment on the cold air intake idea. Years ago, before I decided on the IROC, I used to day dream about building a TA. I always thought the vents at the front of the hood would make excellent cold air inlets. In fact with their location, they might even provide positive pressure at speed(ram air). This would take some engineering to be sure but how cool would it be.

musclecar70sfan

iTrader: (1)

Oh yeah! I'm sure it wouldn't be too hard to make those work... I forgot about that!

BigWhiteGTP

Pretty sure I said mid low 13's, not 12's. My bone stock GTA does a 14.4@94 here in AZ on street tires. A stall alone drops ets by .3 - .6 with drag radials, which I have. Headers, intake, shift kit and gov recal, plus timing advance should make up the difference at least. So mid - low 13's is quite possible with a good running L98. It helps to have a car running factory fresh. Which mine does.

My LT1, bone stock with drag radials did 14.3@95. Not the best time, but comparison, here in AZ stock LS1s are running 14.0s and 13.9s bonestock. With ram air intake, tune, 3000 stall, catback and long tubes it went a 13.0@102. So my GTA is already only .1 and 1mph behind my LT1 and on street tires. It's a reliable and proven mod list.

My car is not my LT1, but in my case, both were similar optioned and my L98 is a good running car. So maybe Im optimistic, but.....it's a Chevy 350 and it responds to basic mods pretty well.

Zepher

iTrader: (1)

what's your altitude at the track, BigWhiteGTP?

I find it hard to believe that stock LS1's are doing 14's while you have bolt ons doing 13.0

I drove a bone stock 2002 WS6 at the track and was able to get a 13.2 @109mph.
I probably would have hit a 12 sec pass if they didn't close the track down due to "cold weather".
I had only driven that WS6 about 40 feet, before I made my first pass, so I had no idea how the clutch would feel, and how much RPM to launch at.
the owner of the car ran a best of 13.5@107 that night.

RED86Z28

My point was its not that easy to run low to mid 13s. Cars with much more power than an L98 with headers struggle with low 13s no matter what tires are on it.

Abubaca

iTrader: (3)

Unfortunately, the corvette aluminum L98 heads (ZZ4 heads) aren't much different than the iron Camaro/Bird L98 heads. Chambers are a little smaller, and you'll get that bump in compression, but ultimately they're the same. Without porting, there's not much more than a weight reduction. So yes, you can do better. It's hard to recommend one head with all the choices out there. I'm saving for the Trick flow Super 23 heads. About $1000 to $1100 for a set. The main thing you want to shop for is an intake runner around 170 to 180. The TPI makes power down low, and won't feed a BIG head. The Vortecs "might" be the best head out there for the TPI, problem is there's no good high flow manifold!!!!!!! DOH!!!!!!! Oh, the sweet irony!!!!!

ASE doc

I hear alot of talk about TPI not being good at high RPM. Like most myths, this continues because people accept it and never actually put it to the test. In 99 when I built my IROC, the accepted wisdom was that TPI was good for 350hp max. Guess I blew that one away when mine made 417hp at 6,000. That was with a smaller SLP cam.

The ZZX cam I switched to later brought my TPI to life above 3,000 and added a solid 500 RPM to the top end. This motor revs so quick I had to set my rev limit to 7000 to stop hitting it every time I upshift from 1-2 or 2-3. And I still hits it at 7000.

As my data reports, my 355 built as shown, revs strong to 7000 and makes good power up high. If you follow the accepted wisdom and go with small runners and a matching small cam, you will get what you get. Or you can follow my recipe and see just what a TPI is capable of.

Abubaca

iTrader: (3)

Never actually put to the test? Have you read any of the posts here?

Nevermind. The problem is terminology. My dremel tool makes power over 10,000 RPMs, so what exactly is meant by "not good" at high RPMs? What is meant, although not often said because it's pretty much a given, is that TPI is "not good" COMPARED to other higher flowing intakes. And this is physics. Not people "accepting" what they're told. There's no point debating your numbers, but let's assume they're correct. Fair enough? Slap a HSR or gawd forbid a Mini-Ram on that beast and you're gonna be selling the TPI as a boat anchor by morning. SOOOO much more RPMs and HP to be had. Again, physics. Nothing to be argued here.
No one ever said that you can't do what you've done. And I bet it's a blast to drive too!! -but you can't take a naturally aspirated motor, give it a high flow intake and a low flowing intake, and expect that they're gonna perform equally. They may both perform well, as in your TPI performing well, but it's not as good as other options.

musclecar70sfan

iTrader: (1)

That's understandable... again I'm not looking for the fastest engine, just something more respectable. And please correct me if I'm wrong, but the TPI is known for making it's torque in the low end, correct? Considering that my car gets driven, I'm assuming that means better gas mileage since you'll need less RPMs to get moving. That would be pretty useful in my case.

RED86Z28

Dont count on better gas mileage.

Abubaca

iTrader: (3)

Musclecar- I wasn't implying the TPI was a bad choice. I was just pointing out to ASE that while his TPI performs great, there are better options for those who want to have their engine perform better in the upper RPM range. I personally love the look, and low end grunt of the TPI.

...and yes, the TPI makes it's torque down low. It's the ole thumb over the garden hose experiment. As the air has to channel itself through the long, small runners, it speeds up, just like when you put your thumb over the water flow on a garden hose. This "charge" of air actually helps get MORE air into the chamber, hence that extra low end the TPI is famous for. Unfortunately, there's a point of diminishing returns, and eventually, it's not able to flow enough air to support high RPMs. Makes for a great streat motor though!!!!!

musclecar70sfan

iTrader: (1)

Better than what? My stock LB9 or a 350 that makes it's power higher up? If it's the latter then I'd expect mileage to be a little better, and if it's the former I don't doubt that fuel economy would be worse.

That's what I'm hoping for!

theimpaler68

iTrader: (1)

http://www.firstfuelinjection.com/

this is the first intake. looks like stock... mostly. lots better air flow. up to 5800rpm i think. this is the way i am going to go.

plug and play with tpi computer

musclecar70sfan

iTrader: (1)

Nice! Thank you!

And I the results mentioned in this sticky seem very promising. 410 hp and 500 lb ft with the stock TPI on a 383?! That's nuts and more than enough for me! I wonder how much it would cost to build a 383 with similar specs. Now this is what I'd like to try!

https://www.thirdgen.org/forums/tpi/...feb-super.html

edit...
found the article!
http://www.compcams.com/Community/Ar...?ID=1737510521

ASE doc

The TPI is a great street motor. Even mine, extreme as it is, is very drivable. Looking at my cam numbers, you would think that I would need a 3000 stall just to pull away from a light. In fact my IROC will putt around town with the best of them.

ASE doc

The FIRST system looks like a good option. It will save you the many hours of porting that I spent on mine.

Stephen

iTrader: (12)

Problem is....Nobody seems to be able to identify WHICH heads they used. Just the brand name, but not models.

I love the idea of building the stock intake TPI they built, for my GTA.

regal301

i dont agree with that.

i swapped in a l31 and its a night and day difference over the l98

regal301

SDPC has a vortec tpi crate motor,dyno'd at 357hp and 416 ft lb

part # sd360vtpi

www.sdparts.com

theimpaler68

iTrader: (1)

muscle i would also put in roller lifters and cam. vast power difference over flat tappets. my 88 has a lo5 350 in it with roller lifters and i plan on the comp xfi268 cam to go in sooner than later.

regal301

his motor has a roller cam.

swap in a (l31) vortec 350,that gets you 250hp,then build from there

came in chevy/gmc trucks 96-00

i like the 305 for what it is..........but you will run into the cylinder fill issue and its no cheaper to build and will give you less power in the end

theimpaler68

iTrader: (1)

was referring to what ever 350 he gets. as being on a budget i bought my lo5 from a guy that pulled it from a 90 caprice police car. got it for a $100. 65k on the motor roller lifters and cam in it. i know his motor has a roller cam in it. i was also referring to camming the 350 he gets with a bigger one. instead of the peanut that comes with most stock ones. he has already stated that he is looking for a used one. we would all like crate ones but that just isn't in the cards now is it.

Street Lethal

iTrader: (16)

But it is still the cheaper alternative though no matter how you look at it. I just started on another TPI setup that I'm buidling for my '84 Trans Am w/355-SBC turbo, and I only have about two and a half hours into it. I still have much more to remove, but as of right now all sides of the intake base look like this (see below). There is simply no way the FIRST setup will flow more air into the cylinder heads than this setup will once it is all finished, and being that the OP already has a TPI setup, it will cost him less than fifty dollars to do on his own. I'm running a finished siamesed setup that I did on my 305 w/T76, and it flows better than all of them in my opinion, and its street legal unlike some of the expensive one's out there....;




To the OP, stick with your TPI setup. Here is one from a C4 w/422 small block in place of the L98, but still using the TPI, Click Here....

Rolling Thunder

After reading through some of the posts there are a few things ide like to note. First off on the 383. Although a 383s is cool and great in a lot of applications I dont know if I agree with using a 383 in this case. For starters going back to the original goal a 350 could easily meet that goal and beyond so there isnt really much use in spending the money to stroke it out. Secondly from a practical stand point we all know TPI isnt the best flowing system out there. Now even though we probably all know this lets look at what this actually means by comparing the 350 to the 383. In the low RPMs the intake flows well enough to do its job and potentially get near 100 VE or possibly even better due to the tuned runners. The 383 has the advantage here due to its size and not being limited by flow rates. This is all great and fine but as we get into the higher RPMs there just isnt enough time to flow enough air into those cylinders to fill them. So as RPMs increase less and less air is allowed into the cylinders. Actually despite the fact the motors are of different sizes they will start to draw in almost the same amount of air because thats the most that can flow through that intake in that amount of time. Again may seem obvious but think about what really happens as result. The force generated in each cylinder would be related to the amount of air fuel mixture in that cylinder times some efficiency and efficiency would be improved with a greater VE. Because of this once you get to the higher RPMs and the intake of air is limited the 350 starts to be more efficient because although the amount of air ingested is nearly the same as the 383s its VE is better so it will have the potential to actually start out performing the 383! So really considering the 350 is cheaper, fully capable of meeting your goals, and a better match for your TPI intake I cant really think of a justification for going to a 383 unless this was going into a truck that needed as much low end torque as you could get.

Second on heads. Your motor will only flow as well as the most restrictive point. Again coming back to the fact that TPI dosnt have the best flow rates in the world a good set of aftermarket heads or even worked over factory heads will not be the bottleneck it will still be the intake. Being that this is the case we should do everything possible to maximize the intakes flow rates. Now as stated earlier in another post the flow rates for aftermarket bases is different between the vortec base and the typical SBC base in the classic SBC base's favor (actually even ported factory bases do pretty well). Because of this as much as I love vortec heads you would probably be better off with the better flowing standard base (or a ported factory piece) and good non-vortec SBC heads.

RED86Z28

The myth that the vortec TPI intake is terrible has been going around for a while but the people who use it are making great power for a TPI.

regal301

got ya.............

i would skip the lo5 swap,it makes less power than his lb9 (if his car was a tbi or carb the lo5 would be good)

vortec is the way to go. tons of those motors out there.

the heads and cam have to go on the lo5 to make power