C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

vett leaving too soft...

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Old Jul 26, 2010 | 05:06 PM
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From: JACKSON MS
Default vett leaving too soft...

i have a 93 auto with ported heads(3 angle valve job) , longtube headers(1 5/8) , lt4 hot cam, 1.6rr, lt4 springs, msd distributor, coil,and wires, 2800 stall, 3.75 gears, and a tune frm pcm for less. I took my car to the track last weekend and was shocked at how slow my car was. This was the timeslip.


60ft 1.94
330ft 5.49
ET. 8.08
mph 86.5

I think the problem is my 60ft time its way slower than wat i think it should be. I have a 2800 stall but my car will only stall to 2100. You guys have any idea as to how I could get my 60ft down?

Last edited by ICANTDR55; Jul 27, 2010 at 02:21 AM. Reason: added info
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Old Jul 26, 2010 | 07:28 PM
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1.9 isn't bad on street tires....might be time for some slicks.

Your ET isn't bad but IMO your MPH seems a little slow/low for the 1/8.....wheel spin?

Stall ratings are not always "exact"....your sure your RPM gauge is accurate?

You might try stalling the convert up at the line just before you launch it vs just punching it - to see what works best.

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Old Jul 26, 2010 | 07:32 PM
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no wheel spin and yes the tach is correct
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Old Jul 26, 2010 | 07:46 PM
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Get a set of good drag radials on it and it will make a huge difference. I have run both the BFG and Nitto street legal DRs, both worked great at the track and safe on the street.
Don't expect them to last long if you use them as your daily driver tires, otherwise they will really help at the track.
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Old Jul 26, 2010 | 08:24 PM
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I guess its a 1/8 mile track? would like to see what it does in the 1/4....tells you a lot more.....
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Old Jul 26, 2010 | 08:37 PM
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If you are not spinning your tires, drag radials won't help. For some reason, you are down on power. Your gearing sounds ok as well as your engine combination. My car can only be footbraked at 2200 rpm as well because the Corvette disks don't hold very well on the line. I would put the car on a dyno and make sure the afr and timing are where they need to be. Maybe if you can datalog a couple of runs, you will find your answer.
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Old Jul 27, 2010 | 02:14 AM
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Originally Posted by 383vett
If you are not spinning your tires, drag radials won't help. For some reason, you are down on power. Your gearing sounds ok as well as your engine combination. My car can only be footbraked at 2200 rpm as well because the Corvette disks don't hold very well on the line. I would put the car on a dyno and make sure the afr and timing are where they need to be. Maybe if you can datalog a couple of runs, you will find your answer.
Well as far as the braking problem wat should i do? And my car does seem to be down on power because it can't even pull to 6500 rpm . Pcm for less sent me a chip for my exact setup so i don't think my timing is off and I put my car on a diagnostic computer and the only problem i saw was my blm(block learn module) was 161 instead of 128 where it should be and i have a bad valve stem seal on my #6 cylinder. How badly do you think its affecting my car?

Last edited by ICANTDR55; Jul 27, 2010 at 02:17 AM. Reason: added info
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Old Jul 27, 2010 | 10:18 AM
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Originally Posted by ICANTDR55
Well as far as the braking problem wat should i do? And my car does seem to be down on power because it can't even pull to 6500 rpm . Pcm for less sent me a chip for my exact setup so i don't think my timing is off and I put my car on a diagnostic computer and the only problem i saw was my blm was 161 instead of 128 where it should be and i have a bad valve stem seal on my #6 cylinder. How badly do you think its affecting my car?
The car is runing "lean" @ 161 would double check your actual A/F ratio as others mentioned.

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Old Jul 27, 2010 | 11:21 AM
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Your car is not just running lean, its running way lean. I would address this problem before anything else, this can damage your motor...WW
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Old Jul 27, 2010 | 11:35 AM
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I am a noob, so what does it mean when a car is running lean? Thanks.
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Old Jul 27, 2010 | 11:44 AM
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Originally Posted by uptown193
I am a noob, so what does it mean when a car is running lean? Thanks.
http://en.wikipedia.org/wiki/Air-fuel_ratio

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Old Jul 27, 2010 | 12:10 PM
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Originally Posted by engle1147
Salute u
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Old Jul 27, 2010 | 07:03 PM
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Have you checked the "official time slip thread"?
I would not call your times "shockingly slow"
considering the modifications that have been made to your car.
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Old Jul 27, 2010 | 07:53 PM
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Does the vette have a AFPR? If so, add some more fuel pressure.
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Old Jul 27, 2010 | 09:52 PM
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what has me confused is that my diagnostic computer says my car is runnin lean according to the block learn module but my 02 sensors are sayin my car is runnin rich and when i put my foot in it i see black smoke out the exhaust. Im lost.
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Old Jul 28, 2010 | 10:37 AM
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Originally Posted by ICANTDR55
what has me confused is that my diagnostic computer says my car is runnin lean according to the block learn module but my 02 sensors are sayin my car is runnin rich and when i put my foot in it i see black smoke out the exhaust. Im lost.
It is very possible that you are only "rich" at WOT (@ wide open throttle - ECM doesn't trim fuel) and "lean" at anything less than WOT......this where a quality tuner that will offer free or inexpensive reburn tunes/tweaks comes in handy. Too "rich" will make you slow too.

Your going to want to do some data logging to see what's going on at various throttle positons/rpms and have your tuner make adjustments. Dyno run(s) will tell you what the A/F ratio is WOT but that is about it.

IMO 60' times aside - your MPH should be much closer to 90 and running upper 7.XX with that setup.

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Old Jul 28, 2010 | 01:30 PM
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so nobody thinks my 60ft is slow? My car is not spinning and im running street tires.
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To vett leaving too soft...

Old Jul 28, 2010 | 01:40 PM
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If you are dead hooking, then yes. I think the 60 foot time is off a bunch.
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Old Jul 28, 2010 | 03:12 PM
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A stock C4, even an 84, should be able to break stock tires loose at the line when footbraking.
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Old Jul 28, 2010 | 04:18 PM
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I know you said you have 1 5/8 LT's. What kind of exhaust system do you have after the headers?

Mail order tunes are an improvement for sure but what works for one car might not work for another one. They all need to be tweaked to get the max out of the car they are in.

Get on the foot brake at the line and load it up as much as you can. Also as mentioned some drag radials will help get that 60' down some. I'd say you should be at 89 mph and 1.8 or a little less with your mods.

What kind of weather were you running in? It's very humid in MS.

Using your 1/8 et and mph this is what a online calculator says your 1/4 should be.

Your 1/4 Mile ET is 12.67 seconds computed from your vehicle 1/8th ET of 8.08 seconds.
Your 1/4 Mile MPH is 107.26 MPH computed from your vehicle 1/8th MPH of 86.5 MPH.

Last edited by Weav's Vet; Jul 28, 2010 at 04:28 PM.
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