1991 c4 corvette L98 engine questions, options, mass confusion.

[Bill Chase]

91 c4 corvette 6 speed car, would like to stay with OEM computer and simply have it tuned.

Application) For a street car, where ac, cruise control and all dash functions are a must.

Desired result) a streetable wide torque curve with a solid 300-320 rwhp.

The good) Love the car, picked it up for 3 grand, runs and drives great. No major problems.

The bad, some years back I owned and drove a 93 f body transam with the 4l60e, and in just about every way it out performed this car in power delivery, I expected more from this car.

With a 4000 dollar budget what would you do? Keep leaning towards a set of afr 195 heads, weiand stealth ram modified to fit under the stock hood, lt4 hot cam, full exhaust and dyno tune, the bottom end is 86,000 miles, solid compression on all cylinders.
But then I see scoggins Dickey has a vortec base manifold for tpi, so I could use a modern head, aftermarket tpi runners, lots of porting and keep the torque of tpi with more power up top.

Sorry to ramble, I just need a solid plan to get to 300 rwhp without sacrificing drivability and creature comforts. And half the go fast parts for these old l98 engines are no longer being produced,

Ligenfelter performances is 1.5 hours from me, but their cnc porting for the 113 heads is more than a set of heads would cost, I have a classic case of too many options, not enough experience, and no local to me shops with experience with the 35 year old tpi setup.

Whatever is done, the car must run, start, drive like an OEM car, not a temperamental race car or hot rod.

I am not even against a carb setup, as long as ac, cruise, and all guage etc can be kept.

[travis]

I think it sounds like a good plan, although I think you’ll be hard pressed to get all that in under budget.

A buddy of mine had an ‘89 L98/4L60 vette...it was all torque and not much else. It launched decent but petered out quickly.

[Bill Chase]

Yeah, tpi does a lot very good, if only they had designed it to pull another 1000 rpms making power.

I suspect that's the exact criteria they had when designing the lt1 of that era, interesting thing is late model vortec heads are essentially lt1 heads with standard cooling. Hence the idea of vortec heads, stealth ram, or the scoggins Dickey base, aftermarket runners and a lot of porting.seems like it is possible, was hoping for some real world examples.

It has also been suggested to go with a 383, custom cam, decent heads and accel super ram, essentially duplicate what John ligenfelter was doing when these cars were the hot setup.

The confusion comes from the 20 years that have elapsed since people were pushing the boundaries of the tpi setup. And parts are not available new. Heads have got better, cheaper, and computers are better.

Out of all you fine gentlemen building engines for a living surely you have clients with c4 corvettes and the gen1/2 sbc and have developed solid efi packages over the years?

[Orr89rocz]

300-320 whp is a walk inthe park.

See if you can find a deal on a set of heads. Even profiler 195 as cast would do it
Chad speier may help there, as cast with a good valvejob and a cheap hyd roller spring package and find a hot cam or similar. That cam drives stock and tunes really easily. With decent heads and intake you can make well over 320 whp. Lt1 cars make 350-360’s easily with good heads and that cam. Pull to 6300-6500

Stealth ram wont fit under corvette hoods. You will need to go miniram or something else low profile like a modded tpi, superram or FIRST tpi. Maybe a efi single plane and low profile elbow. All those efi intakes are relatively expensive tho

Some of the heads/intake choices may not work with egr emissions stuff on those cars...miniram doesnt have egr. Everything else should be fine

Big thing is finding someone to tune these ecms. Not many do it anymore it seems. Most guys have to do it themselves. If you were near pittsburgh pa i could do it

[peejay]

With a 4000 dollar budget, I'd throw a cam in the cleanest junkyard 5.3 I could find and do an engine and PCM swap. Would need an LS6 or LS1 intake manifold of course, and the accessory drive might have to be borrowed from a C5. (Probably the single largest expense involved) The main issue would be ensuring there is room for the A/C compressor.

[Carnut1]

Ported Chevy 083 heads, the tpi project.

This project is stalled at the moment but a good learning experience. I like the vortec head and aftermarket manifold if you can get solid flow numbers from it all assembled. Chad is doing a profiler head with a mini ram for his iroc now. Maybe he will chime in.

[Racer71]

I’d find a TPIS mini ram intake for it that would solve much of the intake deficiency issues

[dfarr67]

Hate to say it- install LS.

[BOOT]

Shift kit, Cam & Intake, then a better efi setup like Holley or FAST retro, both for TPI Otherwise you'll nickle n dime yourself on tunes as you change stuff.

This will take most your $4000 budget(odds n ends) and not get you to your hp goal but get you the best driveability out of it. And then you can tweak stuff like exhaust or when you can afford build an engine or buy a crate, oh and built trans. Otherwise as said LS swap and it's gonna cost more than $4000 up front.

[SpeierRacingHeads]

No LS, that is a crime.

Stock L98 bottom end
Ported 113 heads
TPiS Mini Ram
24lb injectors
Comp 230/236 HYD roller
4060L
4000 stall converter

[peejay]

A C4 that doesn't have the "Tokyo by night" instrument cluster is more of a crime IMO

[midnightbluS10]

Good thing that isn't a C4


Did you already sell that engine you had listed for like $2k on Facebook, Chad? You think it made 300?

[SpeierRacingHeads]

Good thing that isn't a C4


Did you already sell that engine you had listed for like $2k on Facebook, Chad? You think it made 300?

Yes, sold it. I think it made more than 300hp

[peejay]

Good thing that isn't a C4


Did you already sell that engine you had listed for like $2k on Facebook, Chad? You think it made 300?

I'm no expert, I'm not even a never-was-pert, but I had more fuel injector than that and didn't even make 275 at the clutch before the injectors were running static. Unless I'm doing my math wrong again.

[Orr89rocz]

Good thing that isn't a C4


Did you already sell that engine you had listed for like $2k on Facebook, Chad? You think it made 300?

I'm no expert, I'm not even a never-was-pert, but I had more fuel injector than that and didn't even make 275 at the clutch before the injectors were running static. Unless I'm doing my math wrong again.

I’ve seen 350 whp on 24’s but it all depends.

But chads combo should be closer to 375 whp imo but i thought he had bigger injectors