THATGUYWITHTHEBLACKVETTE

Hello, I own a 1992 C4 Corvette with an LT-1 and in my opinion my car is very slow. An average stock c4 corvette with an LT-1 runs a 13 -14 sec 1/4 mile pass.. on my particular vehicle I have made some mods. which are LT4 hot cam kit with heads, 58mm TB, edel brock manifold, hooker headers, borla exhaust, a slight bump up in stock compression, a cold air intake and some very beefy tires in the back, upgraded transsmission with shift kit, custom torque converter for 2500 RPM curve. Not sure what LB injectors I have and I run my 1/4mile no better than a 14 second pass. The take off feels great second gear kicks in with a alot of power but as soon as third gear kicks in my car boggs down.

Any sugesstion on to why my car runs like a stock anything i should check? maybe even a check list of things to check would be appreciated.
#TheGuyWithTheBlackVette

jgalfo

fuel pressure? gas tank usually needs to be full to avoid starvation at the drag strip.

THATGUYWITHTHEBLACKVETTE

the fuel pressure if fine and the tank was not full but had more that 80%

billschroeder5842

If your exhaust is free, then you need to look at fuel pressure and air restriction. That's really were you need to start unless your ignition is WAY underperforming.

Tom400CFI

Need more info. What is your trap speed in the 1/4?
Did you get a tune after heads/cam/exhaust?

If you're really tearing up first and 2nd gear...you should still ET decent even if it falters in 3rd gear. You'd have a decent ET but a low trap. I'm bet you don't have enough fuel....and I'm not talking about what's in the tank. Tank level don't matter by the time you get to 3rd gear.

84 4+3

You could also probably look at the 1/8 time and see how it compares. If you're freight training there and fall off after you have a problem somewhere. Seat of the pants doesn't help, you need data to confirm as your butt dyno can lie.

THATGUYWITHTHEBLACKVETTE

R/T .030
60foot 2.183
1/9mile 9.225
MPH 75.97
1/4 14.233
MPH 101.41

Tom400CFI

There is some telling info. Here is what I can share:
1. Your trap is decent for an LT1, but your ET is bad. What that means is the trap proves that you're making decent hp for a stock or stockish LT1....but you're making an inefficient pass. Where is the inefficiency for your HP? In the 60'. Your 2.183 should be a 1.9x...and that would put you in the high 13's at the same 101.xx. SO...there is some driving work to do there. What is your rear gear? As a comparison, MY box stock '92 runs 101-102 in the 1/4...but has ET'ed 13.75 on that trap. So improving the efficiency of your pass will drive down your ET w/no other changes, IMO.
2. Your ET is very poor for a cam/heads/exhaust LT1. You should be trapping at least 107 or better, IMO...and have a corresponding LOW 13's or even high 12's. The ET shows a massive lack of HP. Again, comparing your car and mine...we're trapping the same speed (making the same hp) and my car is stock....AND I'm running at 4500' elevation on 6000+ DA's. Your car is way down on power. Why? I bet it's in the tuning. You didn't mention if you'd had it tuned after the mods or not.

THATGUYWITHTHEBLACKVETTE

Yes, I did get it tuned when i got all the work done to it but that was 3-4 years ago.

Tom400CFI

If it were my car, I'd assess the mechanical condition of the engine...if sound, then I'd get it on a dyno with a wide band O2 and start trying to assess that tune.

THATGUYWITHTHEBLACKVETTE

Alright ,thank you i will try to get that done and hope for the best i know my car has more power but its not puting it down

ZWILDZR1

Did you take it to the track when the engine was fresh or are you just now (3-4) years later doing it? If just now I would want to check out what the compression in each cylinder is. My other question is do you drive this car a lot or is it a weekend play toy verses everyday driver? Wondering about the miles verses the years after rebuild. Who did all the work? Like has been stated before you should be running much better times than you are. My basically bone stock 96 LT1 with auto trans and the 2.59 rear ran 13.70's all day at the 102-103 m.p.h. trap speed.

ex-x-fire

I'd say a mismatch of engine mods and rear gear. Once you move the power band higher in the rpm range, the more you need shorter gears, like 3.73s.

cv67

Did you check your fuel pressure under load? Id strap that down to a dyno, check your A/F readings and fuel pressure under load.

Could it be an ignition issue possibly....Ive seen cars with weak trans/converters slow a car down but doubt this is your problem. x2 on gears, too.
If you got the 3.07 or worse yet the 2.xx gears this is hurting you. If youre running a sec and a half slower than you should I bet youre leaner than a popcorn fart.

More cam you run the more gear you need so it pulls the way it was designed to. Youll see a lot of the LSx guys run a stock 2 series or 3.15 gears, a big cam and complain it doesnt run the internet #....cause they are worried about mpg and to boot wonder why it acts funny lugging it at low rpm.

Its all a package. Youll find it, usually something simple.

Tom400CFI

No. That might account for the poor 60'...but he should still be trapping a lot closer to 110 and he's not. Gears aren't going to kill your trap by 8mph. He ain't makin' the HP. The trap tells it all.

KyleF

Do you have a fuel pressure gage? Tape it to a window and have the passenger watch it. Does it start to fall off in the upper RPMs of 3rd gear? This would be an easier test before paying for dyno time. Hate to say it could be something simple, but when was the last time the fuel filter was changed?

Do you have any kind of scan tool? Can you watch knock counts? Do you feel any kind of sputtering north of 5K RPMS? Could be your opti.

You say your car feels slow, but has it always? did it feel faster 3 years ago?

Based off your times, I think you need to dial in your launch. Since you are an auto, are you brake torqueing? Do you turn the ASR off to allow a bit of tire spin? On street tires, you will 60' the best with just a slight bit of slip... not enough that the rear is sliding out, but just enough that you "hear" a little chirping. If you are not pushing the limit, you are leaving some launch power at the line.

Sleazy Rider

just a wag here but, do you still have your 48mm throttle body? or access to a 52mm? try replacing your 58mm for either of the 2 mentioned and making a pass. its like putting a 850 cfm holley on a 350 cid. sure, it'll run, even jet it down so it will not be over rich, but, the velocity isn't there.
2 cents deposited.

KyleF

This has been tested (a lot in many magazines) and the larger TB makes a few more HP... literally like 1 or 2 because the engine doesn't need it. Reducing the velocity into the plenum has very little effect since the velocity is developed in the intake runner and intake port in the head. In the carb you are describing, and I certainly don't disagree with it making less power, the fuel is atomized in the venturi bores of the carb and velocity matters a lot. Since the LT1 is fuel injected into the runners it is not the same as the carb. What it will do is make the throttle more touchy in normal driving conditions due to a larger inrush of air at any give throttle angle.

Tom400CFI

No man, this is bad advice. It's nothing like your analogy of a carb that's too big. Why not? Because a carb requires velocity through the venturi to pull full out of the bowl. The OP's engine is EFI. Fuel is pumped through the injectors....no vacuum or velocity needed to get fuel into the intake manifold. TB sizing changes throttle tip in sensitivity....but velocity is not a requirement of an EFI TB. Lore.

bjankuski

I agree, the power is down. Do you have CATS on the car?