L98 Power Numbers
 

Hi Guys,
I have the chance to buy an '88 350 with ported aluminum l98 heads, gm hot cam kit, carbureted conversion, and dual plane intake manifold. the seller claims this combo will put out a little over 400hp and 400tq. Does this sound about right?
Thanks!

Others will way more knowledge than me will chime in. Those numbers sound like a pip dream. The car is about 240hp 355tq stock. Maybe it does have 400lbs tq. I just cant see how it would be 400hp, Does the car have headers, any exhaust work? It would def need a custom tune since it's no longer a TPI car.

That's what i was thinking. Yes it will have headers. From what I have read, the main restriction in the L98's was the TPI and air flow issue. The heads are supposed to have some heavy porting on them, along with the new cam, intake, and carb I thought that there would actually be a possibility of those numbers. I can't reallly find any information about this type build though.
Your guys' help is greatly appreciated (:

Yeah...those carbs are tricky to control! Really, it's quite hard to find someone who computer tunes a carb anymore!

:yesnod:

Not true. All you have to do is find a shop that sells "Muff Bearings", "Headlight and Blinker Fluid" and they can do it. :rofl:

On a serious note to the OP. How do you know it will do what he says it will do? Can you drive it and see if it has street manners? How do the gauges work? Will you be able to dyno it?

It is just the engine. Not the car, sorry for that confusion. This is my main concern, before i spend a little over $1500, i want to know it will perform as he states. It has >10k on the short block and the cam kit and heads are brand new.
I just found this article: http://www.hotrod.com/techarticles/e...n/viewall.html
Stock, using a carb and new intake, they got 329hp and 393tq. This makes the seller's claims seem more realistic.

oh, and i reccomend you guys check these guys out http://kalecoauto.com/

It MIGHT do what he says, it might not. If you want to be sure, get an engine dyno and test it. Either way, I am not a fan of ported heads unless you know who ported them and for what application.

TPIS built up a '91 TPI Vette and got ~360chp so a properly done carb unit might hit 400chp, IMO, because peak power would be higher on the RPM scale.

That said, if he dynoed the engine only, you would see less with all accessories running in a car.

I was wondering where you would find a leak control adjuster since that is what a carb is, a leak controller. :D

Honestly I think going to a carb was a step in the wrong direction. They sell intake components to let the engine breathe easilier that would also allow a more equal amount of fuel to each cylinder.

Plus you also lost your gas mileage indicator I believe.

KaleCOAuto...good stuff there! Recently, there was rebuttal on the theory that a hot engine makes more power. I clearly remember former member CFI-EFI argue the merits of why a hot engine made more power. I should have sent him this link!

If you pull an L98 from the car and put it on an engine dyno, your chp/ctq numbers will jump. Pull that TPI, install a cam, port the heads, and install headers....yes it's possible to get in the 400chp/400ctq range with a 350. That "only" means hitting around 340rwhp in the car....and that's been done. People have gone higher. With 350-355 LTx cars, people have broken the 400rwhp/400rqtq barrier. That's with AFRs/cam/modified intake/headers.

In my mind the question is whether you trust the builder's assembly skills more than his claims for power.

It could be close to 400 HP with 400 TQ, if the combination was put together correctly.

My 355 cu/in TPI generates 425 FWHP and 510 FWTQ...so the carbed version should easily do it with the right stuff inside it.

Problem is KNOWING what is in there...I had mine built, so I know what the components are and we matched everything to work together.

I know what was done to my heads for porting...a CNC work of art!

My suggestion is a chassis dyno...as long as the engine is still in the car. Figure a 17% driveline loss for a C4 and you'll be close to your crank values.

510tq from a 350? Did you mean 410?

No...I was 397.56 HP & 487.8 lb/ft at flywheel before I Siamesed the intake and we finished tuning...

I'm now at 425.3 FWHP and 510 FWTQ (353 RWHP/423 RWTQ)...nice for coming out of the corners hard. :D

Granted...I run out of RPM's faster than the LT1/LT4 guys, but if you get the big jump it's hard to make that up by the next corner.

And yes...it's a 355.

Well I feel confident in the seller's claims and from what ive gathered from you guys it's not all that far fetched if done right. I'm picking up the motor on saturday so i will let you all know how it runs when i actually get it put into the car. I would be extremely pleased with the 340whp range.
I feel that this engine is also a pretty good platform to build on, I dont really believe in the "dont build a 2 bolt main theyre weak" argument, so this engine might see a 383 stroker or maybe even a little 144 blower in the future. I'll keep you all updated with the progress, hopefully this helps out others in my position too,
CHEERS!

What RPM are your WOT shift points??

I start to nose over just over 5500...

But with the torque curve I can pull the higher gears. It's a balance...

When I built this thing...I wanted it to be stealthy. I wanted to explore the boundaries of what a TPI COULD do...and I'm pretty sure I've gone as far as I can with this one.

When I first took it to National Convention and pulled into Tech...and they looked it over and said "What's Group 3 about this?" I knew I'd accomplished part of my goal.

I'm pretty sure with nothing more than an intake change I could easily see 450-475 FWHP...but since I'm building a dedicated track car I think I'll just leave her be for now. It spins the tires in the first 3 gears at will...just need to add a little more throttle and she lights them up. :D

Engine:
355 ci L98 with 52MM Throttle-Body, Ported Plenum, ASM Runners, Accel siamese-ported base plate, 24# injectors, 1.6 rollers, 218 CFM CNC-ported stock heads, Corvette Challenge cheater cam, 10.6:1 compression, Canton Road-Race Oil Pan, Ron Davis Aluminum Radiator w/Integrated oil cooler, 180 Deg. Thermostat, TPIS Jet-Hot coated headers, Formato custom chip

Drivetrain:
Single-mass flywheel, CenterForce Dual-Friction clutch/pressure plate, Hurst billet shifter, Poly bushings, Mid-America lowering kit, 295/30YF18 BFG k/d's on OZ 18"x10" Monte Carlo Rims, Doug Rippie suspension modifications, Bilstein custom-valved FX3 shocks, GM DuraStop "Performance" Drilled/Slotted rotors & GS calipers

Exhaust:
3" Random Tech "bullet" cats, Corsa LT1 dual exhaust

This was at our car show a while back...a "burn out contest". I got 2nd place :toetap:

PSA time :D
The ideal engine for street strip daily driver type vehicle is 05-07 5.3L L33 from certain Silverado trucks

Reliable to 300,000 miles and supports 1000 horsepower.
Weighs less than an Iron 4-cylinder engine from Nissan or Toyota.
Untouched bottom end engine internals (do nothing to it to maintain reliability)
Available everywhere and affordable

Alternatively, there is a cheaper version 5.3L "LM7" from 2002 Silverado, Escalade, etc...
Same displacement but +120lbs of IRON block
Much cheaper (got mine for free) have spares I can't give away
Only supports around 700-800bhp (I am comfortable around 620rwhp)
Same reliability 300,000 miles, 30 years

In my sig is an example build. In 2017 I put a 180,000 miles LM7 at 3000lbs and as of today have 42,000 additional miles on it at 500-600rwhp
The engine was free from a local junkyard (they gave me their most filthy forgotten one)
It was supposed to be a test engine, because it was my First LS engine ever I was worried I would damage it. But it turned out to be perfection incarnate and now I can't remove a perfectly good engine from my car. So I am putting together an L33 on the side while I wait.

Yes it is expensive to convert over to the LS style engine but the benefit is you will never have to buy expensive engines or engine parts again. No more need to modify them. Modern seals means no more leaking and smoking (if you've done everything right).

Esoteric Secret: The key to keeping them fully reliable and smoke/leak free is to use a fully functioning Factory PCV system and monitor the crankcase pressure carefully. This is the one major failure/flaw I see rampant in the performance/modifications people are doing unwittingly causing oil aspiration and oil related issues because crankcase pressure is rising over atmospheric and they are not measuring it nor have any knowledge of the importance.