I have a 1990 C4 L98, auto, pretty much stock except a few mods injectors 30LB and cat back and 3:73 gears. The L98 is not known for performance and about 4200 RPMS it falls on its face, Its almost like someone puts their hand over the air intake, I have the option to pick up a 325hp / 350 all dyno work done with a dual plane intake and 750 carb,
OE cylinder heads
OE crankshaft and connecting rods
Hypereutectic flat-top pistons
Hydraulic flat tappet camshaft
465 int./.488 exh. cam lift
224 int./234 exh. cam duration @ 0.50
9.1:1 compression
the stock motor has 30Lb injectors what else can i do to the TPI to enhance it up to about 5500/6000 RPMS, i am changing the cam to a longer overlap, thumper cam all roller and a 2200,2400 stall converter, this is a fun car not a daily driver, complete new interior is here waiting on the engine work to be finished,new fiberglass targa, ZR1 rearend, a few other things, My biggest question what can i do to wake up that TPI, i have been collecting parts all new sensors for the entire motor along with new fuel pump , I want the same style of romp i get from my 69 torino 428CJ 4 speed, 4:11 gears, i think it should be a fast Vette but something i am not totally comfortable with is holding it back ? thanks for any help guys , any comments and ideas are appreciated,

 

There are many, many threads on this. Use the search function and do a lot of reading. The main point is to change the intake manifold to make power. My 91 has the same engine as your 90 and I put down 310 hp to the tires (~365 hp crank) with intake, cam and exhaust mods. You need to find a good tuner also. Spend some time looking through old threads and you will learn what you want to know.

 

If higher revving is your goal, intake and a cam should get you there. L98s weren't built for high revs, they were meant to make power quick and early in the rpm range (like a truck engine, really). Exhaust work would help too, as the stock manifolds aren't meant to move air at high rpms well.

And of course, a tune when you've finished your mods is usually a must, especially if you are shifting the power band.

 

I have all new headers and exhaust system on the way , 4 row aluminum radiator new fans, stall converter and a few more things i am changing out, i have read this link several times and its a good piece but it was done in a shop on a Dyno not in a car that had to have ECM worked on or removed, http://www.powerperformancenews.com/...tion-upgrades/ its always different in real world set ups, anyone have any thoughts on their test and results ?

 

what gear ratio do you have?

If youre going with a biggish cam more compression is ideal;smaller combustion chamber, better piston or both;possibly a larger converter too as the 22-2400 is practically stock

Lots of cams that work, those thumpers are meant to sound bigger than they really are. Theres better stuff out that have better manners and make great power. Lots of cams out with gimmicky names seems to be the trend.

 

If its a 90 auto, the question is what gears came in it, probably 2.59s, so you will want to change that to 3.07 at a minimum, but the intake choice will come into play here.

I would tell you to leave the converter at 2200-2400, this is what I run behind my 398. I would not run more for the street, but if you were wanting to race the car then you may need to go higher, again the intake choice comes into play here.

I'd like to know the specs on the heads to give a better recommendation.

If you are going with a cam that size, I would go with Miniram, but will need larger heads I'm thinking.

 

long tube headers, Motor is built and i will have it shortly 355Cuin, 375 hp at 5800 rpms,staying with the 3:73 gears , took two of our show cars to a show this weekend ,saw what everyone had done to their vette, A lot of different stuff but the only thing in common was tossed the factory TPI, Had the luck to talk with a Chevy Tech who had a street rod there, He explained about the TPI was designed for the 305 was never intended to be used on the 350, But someone had to do it, And it was a nightmare for the dealerships and really hurt corvette sales until someone stepped up and started with the ZR and LS option's along with others, My motor will have angle plug heads, Cast iron, aluminum dual plane intake and a carb, Hood clearance is a question but at the show a C-5 with a upgraded intake and TBI 4BBL style holley injection system had a 2 inch Z28 style scoop looked fine, Chevy guy gave me his number and said once its in the car and running he can give me a wire diagram to follow so that all the electrical gauges will work, and using dummy loads and bypass'es make the computer think its still doing something., Also gave me a look at his street rod and how he used a 90 vette trans with the TVV cable, a lot learned and more to figure out as i change the lamb into the tiger !

 

The ZR-1 rear end? Are you referring to the Dana 44? it is the same as any later model C4 with a ZF6 3:45. or the rear bumper cover if so it will not fit as it is 3 inches to wide. The standard 91 & later style rear cover will fit but you will have to add the third brake light in the center.

 

, ZR1 style rear bumper cover, really a C5 conversion and C5 front bumper cover also, One of my Corvette friends bought an original ZR1 and cut the center glassed it and covered corvette and cut in ZR1 , backed with smoked plexi and lighting behind it , options are wide open at this point.