3rd Gen / L98 Engine Tech 1982 - 1992 Engine Related

Want more power out of 350 tpi?

Old 11-07-2009, 06:20 PM
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Want more power out of 350 tpi?

posting this for a friend..right now i have a 1988 iroc camaro 305 with a 5 speed tranny. i want to put in a 350 block and transfer my tpi setup over. i know ill have more hp but im looking for over 300-350..can i achieve that with the stock tpi intake? what will need to be done to get there with this setup or should i do something else..thanks
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Old 11-07-2009, 07:11 PM
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Originally Posted by dragginS10 View Post
posting this for a friend..right now i have a 1988 iroc camaro 305 with a 5 speed tranny. i want to put in a 350 block and transfer my tpi setup over. i know ill have more hp but im looking for over 300-350..can i achieve that with the stock tpi intake? what will need to be done to get there with this setup or should i do something else..thanks
Everyone is going to hound you to get something else and forget the TPI. I think it is doable for the power you want, but if you're talking RWHP, i think the T-5 trans becomes a problem (GM only put them behind 305s for this reason, 350s make too much power to warranty back in the day), unless you don't mind it going out later and upgrading to say a t56 or something. Otherwise it is recommended to use nitrous i guess. I'm sure someone who's a little more familiar will post up, but usually the main argument is that the money you will spend on upgrading the TPI intake, could be better off spent on a different intake system. Good luck
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Old 11-07-2009, 11:05 PM
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do you think swapping an lt1 would be better/worth it then staying with the tpi
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Old 11-08-2009, 12:50 PM
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bump
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Old 11-08-2009, 02:43 PM
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Originally Posted by dragginS10 View Post
do you think swapping an lt1 would be better/worth it then staying with the tpi
I'm not too well versed on LT1s but i know they are more capable than TPI set ups. If you're willing to swap, i would recommend a LSx swap, but a LTx would be a huge step above TPI. I think you can buy a lower mileage LS1 engine T56 trans combo for $2500 any day (LTx would obviously be less), and there are deals to be had on them if you wait and search a bit. But this is all just my opinion, do what you want to do!
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Old 11-08-2009, 10:08 PM
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TPI is good enough for a stock 350 engine but if you want to break into the 300hp range, you'd need a lot of upgrades on the engine and the intake would become the most restrictive part.
You can port the stock TPI intake to allow more airflow through it, you can buy a higher-flow TPI intake and runners, or you can switch to a different intake style. However, the last option would completely destroy your engine's low-end torque (which the TPI is famous for) and economy.

Btw, a 300+hp engine with stock TPI intake is possible, been there, done that.
And it spanks LT1's and LS1's from red light to red light.

Lou
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Old 11-09-2009, 12:12 PM
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Should be easy to do. I got 390's RWHP out of my 87 Vette using Ported stock heads and an LT1/4 Hot Cam Kit. I did use the SuperRam intake though, adjustable pressure reg. and 24 lb/hr injectors.
And I didn't "loose" any torque!!
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Old 11-09-2009, 12:30 PM
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Originally Posted by Z28SORR View Post
Should be easy to do. I got 390's RWHP out of my 87 Vette using Ported stock heads and an LT1/4 Hot Cam Kit. I did use the SuperRam intake though, adjustable pressure reg. and 24 lb/hr injectors.
And I didn't "loose" any torque!!
390 is a very respectful number from an L98 block, congratulations.
Though, did you mean 34 lb/hr injectors? 24# injectors would not support 390 hp unless you double the fuel pressure to 90 psi.
Did you do your own tuning or did the MAF system pick up the extra airflow with no problem? Speaking of MAF, did you have to upgrade the sensor?

Lou
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Old 11-10-2009, 10:16 AM
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Originally Posted by BigBadLou View Post
390 is a very respectful number from an L98 block, congratulations.
Though, did you mean 34 lb/hr injectors? 24# injectors would not support 390 hp unless you double the fuel pressure to 90 psi.
Did you do your own tuning or did the MAF system pick up the extra airflow with no problem? Speaking of MAF, did you have to upgrade the sensor?

Lou
This was many years ago, so could have been 34's. It started and ran on the stock tune, but was then "tweaked" on the dyno. Only increased the fuel pressure a couple of psi, no where near 90.

P.S. Could have been a "generous" dyno too. Sold it before I ever had a chance to confirm HP at the track.

Last edited by Z28SORR; 11-10-2009 at 10:19 AM.
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Old 11-10-2009, 01:41 PM
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Originally Posted by BigBadLou View Post
TPI is good enough for a stock 350 engine but if you want to break into the 300hp range, you'd need a lot of upgrades on the engine and the intake would become the most restrictive part.
You can port the stock TPI intake to allow more airflow through it, you can buy a higher-flow TPI intake and runners, or you can switch to a different intake style. However, the last option would completely destroy your engine's low-end torque (which the TPI is famous for) and economy.

Btw, a 300+hp engine with stock TPI intake is possible, been there, done that.
And it spanks LT1's and LS1's from red light to red light.

Lou

Lou can you tell me what you did exactly to get 300+hp with the stock TPI
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Old 11-10-2009, 02:16 PM
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PM sent, no need to litter this thread.
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Old 11-10-2009, 06:45 PM
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Thanks for not sharing tech info in this forum.. We have 923 guys trying to make a TPI car go fast and you can't cut and paste some text... nice.


Can somebody rename the forum "Big Bad Lou's Secret Power Forum - PM for Details



Injector note.. we have a board member here named Steve Q that ran 24lb'ers in his N/A LT1 car well into the 9's. Nothing wrong with a little extra pressure. I recalll him saying 75+psi. I ended up buying them when he parted it out.

Intake note... Nitrous doesn't discriminate. TPI, LT1, Hogan Sheetmetal... Nitrous politely enters ANY intake design and proceeds to get the job done.
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Old 11-12-2009, 11:18 AM
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Dan's secret recipe

300 RWHP from TPI: (from memory so it might not be totally perfect)

1) Good, ported heads, preferrably aluminum, shoot for 10:1 to 10.5:1 compression ratio, set up to handle a valve lift of .575". Target airflow: 260 cfm intake, 235 cfm exhaust @ 0.5" lift. Probably a 180cc to 190cc volume on the intake side. You need to measure your piston dome volume, your piston-to-deck distance at TDC, and your gasket thickness in order to compute the required combustion chamber volume to hit the target compression ratio, but the volume should fall around 58 to 60 cc, I'd guess.

http://www.sdparts.com/product/AFR09...Riser65cc.aspx

2) Hydraulic roller cam with 1.6:1 ratio roller rocker arms, 112 to 114 LSA, 110 degree ICL, of no more than 224 degrees duration on intake, and .540 to .550" of valve lift. Comp Cams XFI series might be a good place to look. Try to get a post 1987 block if you do this, and you'll save a few bucks by reusing your 305's lifters.

http://www.compcams.com/Cam_Specs/Ca...?csid=208&sb=0

3) You are going to need an aftermarket intake and runners. No way around it. Either replace the whole thing with a Holley Stealthram or else find a used set of SLP runners and a used base. An option would be to get some Vortec heads from Scoggin Dickey and user their TPI base, if they still sell it. Then have the plenum match ported to your new gasket set.

4) No more than 52mm on the throttle body.

5) 28lb injectors. 30 lb injectors are good for nearly 400 RWHP and you don't need that much fuel unless you are injecting for dry nitrous shots.

6) Decent headers, 1 5/8 primaries. Edelbrock TES was good enough for 400 RWHP and 12.4 second runs for me in 2005, believe it or not. All you need to do is make sure the welding flash is cleaned out of the flanges with a die grinder. Hooker also made a good budget line of headers. The Hooker Aerochamber cat-back also rocks.

ECU programming. Craig Moates makes some good programming tools. If you aren't good at it, do yourself a favor and budget $500 for a day's worth of tuning at a tuner shop with chassis dyno.

This should get you a 350 TPI that can rev to about 6000 RPM & make the 300 RWHP, perhaps even 350 RWHP.

I want to hear how it turns out.

Last edited by ws6transam; 11-12-2009 at 11:31 AM. Reason: Did some quick shopping for you but YMMV!
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Old 12-26-2009, 12:57 AM
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1990 L98 dyno'd at 289rwhp, 398 rwtq

- factory cam and heads
- edelbrock headers, mandrel pipes, dual hipo cats, 3 inch i-pipe, flowmaster 40
- under-drive pulley
- 1.6 ratio roller rockers
- Jacobs ignition system
- Arizona Speed and marine intake and LTRs, fully ported an matched plenum, intake and runners
- new wires, distributor, ign module, EGR and so on just to be sure no mickey mouse issues ******* me
- factory prom, its an SD car so I figure why bother until I change the cam and fuel mix?
- the dyno was last taken on a 48mm TB I have a 58mm now. SOTP is about 10-15hp. Have to wait till next dyno to see?

lotsa brakes and suspension mods. But thats about it for go-power.

I swapped a WC T5 for the auto.

for those who like factory comparisons:
289rwhp * 1.15 = 332chp
398rwtq * 1.15 = 454ctq


Typical TPI hp to tq gap. I am working on a cam/head upgrade this winter that should even it out about.

Easy to make power on a TPI. Am on my 4th car its old hat by now.

Last edited by palric; 12-26-2009 at 01:00 AM.
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Old 12-29-2009, 11:22 AM
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300 horsepower at the flywheel is plenty doable with bolt-ons on a stock TPI engine, but it'll require changing the intake, adding headers/exhaust, and 1.6 roller rockers, etc. An LT1 engine is simply a TPI engine with slightly better heads and an intake manifold that doesnt restrict above 4500 RPMs.

My first combo was a ZZ4 camshaft, ported Corvette heads, SLP 1 5/8" headers, ported stock intake and runners, flowmaster 3" exhaust, 1.5 roller rockers, etc. That was good for 282 RWHP and 380 RWTQ and 13.23 @ 107.19 MPH with sticky tires and a T5 tranny.

Then I went to the LT4 HOT cam, Dyno Don's 1 3/4" headers, ported TPIS intake manifold and long tube runners, 1.6 roller rockers. and a 3.5" cat-back with Magnaflow muffler. That was good for 12.80 @ 108.50 with sticky tires, but I broke the T5. It made 319 RWHP and 418 RWTQ.

Now I'm using ported Trick Flow heads, siamesed SLP runners, super-ported TPIS intake, and a Lunati 226/232 camshaft. The HP numbers are in my sig but I have no new track results. I also switched to a T56.

If I was to do it again I would go straight to the Trick Flow heads, or the AFR Eliminator 195's if I had the money. Also the Comp XFI268HR-113 camshaft has shown to be a very strong performer in TPI engines.
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