Ive always wanted a turbo vette, as i now have the vette part covered i just need the turbo. Can anybody tell me if a rebuilt L98 can take some boost? Not crazy psi, just enough to give it more punch when the torque drops off.

 

Depends on how much.

L98 has two bolt mains and a cast crankshaft, not the best choice.

 

..... Boost the L out of it ! ..................

 

I used to "bust an L "we lived in a small town and thats what we called cruzin the 5 minute strip.

 

What year is your car? If you haven't done the rebuild yet, I would talk with your engine builder about what you want to do. I would certainly go with a forged crank, forged rods and good pistons made for turbo/blower engines. 4-bolt blocks can be had and that saves the original block (it will have the matching VIN number) The builder will want to know how much boost you intend to run so he can recommend the correct parts.

Rebuilding the engine is one thing, making a lot of HP and torque can play havoc on the rest of the drivetrain. What trans is in the car? Automatic-equipped C4's got a Dana 36 differential and it's weaker than the D44 that came in cars with a manual trans.

The stock TPI intake is going to limit RPM to some degree; stock L98's don't have much left beyond 5000-5200 RPM or so. An aftermarket intake like Accel, Lingenfelter, or even the Edelbrock intakes will be a big help just by themselves. And with a turbo, you will most likely need to have a good exhaust system designed with a turbo in mind.

You might be better off by looking at a cam and some head work, headers, and a good tune.

 

Ive got a 90 with the factory 6 speed. The motor was rebuilt to stock specs before i bought it and then was driven less than 3,000 miles. Ive got headers just not installed just yet. Something else i dont know is the kind of power/tourqe the factory trans, rear, and such can be expected to hold. Im not looking for huge hp or torque numbers, 350/400 would be perfect for now. If im looking at replacing internals, heads and such to get those numbers i would rather LS1 swap it. Ive always wanted a turbo v8, to me a vette is the perfect platform.

 

Full engine swap expense can get out of hand in a hurry if you don't have all the details (as much a possible) in order.

The L98, just like pretty much any other engine, can take boost. To be safe, you want to stick to about 5-7psi boost on the stock bottom end. I even ran 9psi on my stock LT1 without any issues.

Turbo kits are not available (as far as I am aware of). Custom jobs will be expense. If you're ok with a superchargers, contact Gregg Carrol at "blowerworks". He offers several options that are incredibly well sorted out. If you source a basic kit from say procharger, you'll end up going through a series of alternations/modifications to improve/correct the standard kit. This is why people go to Gregg, to avoid the headache.

 

Don't worry...

if you have a tight L-98, fresh rebuild it will handle up to 8 psi no problem as long as you do not over-rev it and scatter it with stressful high rpm Deceleration...ex:, don't smoke tires and spin it to 6000 rpm THEN just let off the gas and force the engine to absorb the sudden reversal of the stress...that's fatal without forged parts.

And another thing, the rpm that's its capable of turning and making usable, real HP is limited by the cam in a forced induction engine, not the intake. The intake has less to do with it when the induction is now positive pressure (forced) and no longer vacuum...BUT, with the stock bottom end you won't be seeing more than 5500 rpm if you want to drive it home.

The others are 100% correct...the RIGHT way is to build the bottom end with a forged crank, good rods and some forged pistons. THEN you can pretty much do what you want with boost and chargers. Stock, about 8 psi, maybe 10psi IF you only jumped in it on RARE occasions. ... and still stayed out of the 6000 range. Its not balanced for that and the stress is unbelievable at those rpms.
8psi is a good number for more DD activities and that won't require a huge investment. You can probably do this for $2000 if you do some of the work yourself. Chargers of ANY kind aren't cheap. The secret to turbos is the intercooler. Gotta have it and THAT is also the hard part. Where to stuff all that and how to keep the engine cool with hot exhaust now being circulated under the hood. You will learn as you go but be forewarned, it IS more complicated than bolting on a turbo and clamping up some ductwork...lots more complicated.

The alternative is to "bottle blow" the car, which is doing the exact same thing as forced induction, except the no2 has to be refilled so its costly to use but NOT a problem to have as long as its not used. The engine remains basically just as it IS, until you hit the button...then its "blown" for the next 2 or 3 seconds. Stress is limited to that period and NOT every revolution of the crankshaft. Nitrous is lots cheaper as well. You can install the kit on a weekend in the garage without outside help. With either method of stuffing
o2 into the combustion chamber there needs to be a "tune" to recalibrate the ECM to the new fuel/air that its eating. I cannot tell you how much Nitrous the stock engine will tolerate but I DO know many guys that have used it and lots of it, without exploding the stock motor to pieces as long as they don't go hog friggin wild...I knew of one guy that gave his a heavy dose and ran it at the strip all the time...and never had issues until it got to be a high mile motor and it finally let go. 150,000 miles IIRC..

 

Thanks thats just the kind of info i was looking for. And going to the track or really running it hard isnt what i have it for anyways, i drive it everyday during the warmer months so the mentioned 7 psi of boost i think will be fine. Even when i have some fun with it i shift at 5,000 rpm, after that i really seems to drop off so whats the point. Eventually i will motor swap it, ive seen a few 383s with the tpi intake on it so maybe thats the way ill go. Untill then i will highly consider the centrifigal supercharger setup, as long as it doesnt have me changing the trans and rearend, ect.

 

350-400 hp isn't all that difficult. it can be done with a cent charger, nitrous shot or just cam, intake & exhaust work.

Again, your power band WILL change and the 5500 rpm 'dead zone' will go away when you have forced induction. The reason that there IS a drop off is because the TPI is soooooo long and that creates vacuum issues that can no longer be overcome by natural aspiration at that rpm and above. if you notice the LT engines and later ls and lsx, the runners get shorter and shorter to solve this problem of top end power loss.
The cure for ANY of that is FI or nitrous. The goal being stuffing as many o2 molecules in the combustion chamber as possible to yield more energy when the "charge" is detonated.
personally, I would seriously consider the Nitrous. You are not going to be a happy camper when you get into the belt driver chargers and intercoolers BS. The hassles can be endless and expensive...And like I said before, the nitrous is like its not there, your engine is box stock until you hit the button. With a charger you are always forcing more air inside generating additional heat...and wear. Theres no turning a charger off.
Good luck. I'm sure you will enjoy the journey as much as the destination..

 

That's not true.



That's not true either.



No.


Nope.

Lot's of bad info ^there^, unfortunately.

 

I have run 8 psi intercooled boost on my std l98 for 6 years no problem at all.
When i built my 383 with forged steel crank, rods and forged pistons i kept the TPI intake cause it looks great, guess what i accidently spun the 383 over 6,000 rpm during running in several times. So if you have a turbo or a blower they will force the air thru the long runners.

TPI may not be the best intake for max rpm but i have seen 6,500 rpm lots of times, if i wanted to rev to 8,500 rpm well then i would have to go to a different intake.
But why i have a mountain or torque from idle that just multiplies as the rpm goes up and have no need to rev past 7,000 rpm, would mean different camshaft,heads intake etc.

Have been there with 8,500 rpm screamers .... they do not last think about critical piston speed yes they will do 8,500 rpm but the bore wears at an incredible rate.. had a dropped valve after 3 months (need new collets every 2 months) after i split a bore i saw the 6 month old engine had a massive lip in the bores.

I now have more HP and torque at half the rpms totally reliable, turbos are now common place with factory cars that have 3+ years warranty
as long as the tuning is right you will have no issues with 8 psi boost.

When i disassembled my old L98 with 170,000 miles on it she looked great, no piston damage ring landings all good bearings were great. She would just have needed a hone and new rings to do another 170,000 miles, also there was no bore wear that has taken 6 years of 8 psi boost without issue.

Yes your transmission will need major work to withstand more h/p the half shafts will break they twist easilly, i have steel ones and my dana 36 still lives

 

It has been a couple of years ago. They twin turbo'd a Corvette. If I remember right, they put the turbos in the rear fenders. It seems like it would have major lag back there. It may have been Stacey David, I am not sure.

 

Boost doesn't generally change the SHAPE of the tq curve. It simply raises the elevation of the entire curve. Yes, you are making more power at "6000 RPM" (for example) than a stock engine, but you are still, way, WAY past the power peak in an L98. The intake harmonics don't change just b/c you added boost.

http://www.vetteweb.com/tech/vemp_06...photo_11.html#
From ^that^ article:
"The TPI induction system was a major factor in determining the shape of the torque curve. The long runners promoted low-speed power but restricted horsepower production past 5,000 rpm....The steady diet of boost from the HP turbo kit simply elevated the engine's power curve without changing its basic shape."

Another boosted L98 example cited in the same article...
"Whereas the '87-spec L98 produced 240 hp at 4,000 rpm and 340 lb-ft of torque at 3,200 rpm, the twin-turbocharged B2K engine-which used OEM cylinder heads, a factory TPI intake, and virtually stock cam timing-produced 345 hp at 4,000 rpm"