kopbet89c4

Would anyone have a dyno sheet? Just wondering, I keep on hearing that the L98s are WAY underrated. I know my supposedly "stock" L98 /w a 700R4 automatic trans /w 3.07 rear end ran a best of 13.76 @ 104 MPH /w a 2.0 60' AT THE STRIP! I'm totally impressed. I thought I would do way worse than that since I hear 89 L98s have only a meager 250 hp stock . The worst run was a 14.19 @ 103 MPH /w a 2.18 60'. I had a fifth of a tank of gas and my car weighed 3200 lbs with me in it. Wheels were some 17x11 ZR-1 /w 315/35/17 drag radials I borrowed from a fellow Vette owner at the strip. So what would be an appropriate guestimate on HP and TQ at the rear wheels? I watched the tach the whole time and all shifts seemed to be right before 5200 rpms. I'm beginning to think this Vette is NOT AT ALL stock like I always thought when I got it for a trade.

cv67

That's a strong running L98!

kopbet89c4

Before I ran, I did a compression check on all the cylinders. They are as follows:

#1 199 psi
#2 205 psi
#3 208 psi
#4 200 psi
#5 198 psi
#6 200 psi
#7 207 psi
#8 200 psi

What are the usual numbers for a stock L98? These numbers I got are awfully high up there for a domestic. The previous owner must have milled the heads, or got better pistons. I don't really want to bother taking off the heads, until I have to. I'm also guessing that the compression ratio would be like 11:1 since those are the same range of numbers I got when I built my first Honda for all-motor performance. Back then, it had 11:1 compression pistons with a stock displacement head.

Edit: Cyl #8 should have started as Cyl #1 and so on... Go backwards!

bogus

The head gasket is ok.

The real test is a leak down... that will prove if the cylinders are good.

Looks like you got a Wednesday Motor! Congrats!

kwik_ta

Those are rather impressive for a stock L98... Either way, you are planning to hit 10's right??? so stock numbers don't mean much right now. Get a nitrous kit and pill it til you kill it.

scorp508

The ET with drag radials sounds about right, but the MPH seems a tick high. What were the weather conditions like? It isn't a far stretch of the imagination at all to believe that car is stock if the weather was good.

kopbet89c4

It was sunny and hot and the usual humidity Florida has. I'm now actually thinking this car isn't stock. I'd like to investigate the previous owners' mods to see what they have done. But its definately running strong at almost 120K miles and the tranny shifts like a manual and barks the 315 tires among shifts. Would this mean I may have a shift kit and don't know about it?

Fozzy_Bear

I never scanned it in, but I can tell you all about it.
The TQ curve looks like the arch in St.Louis. That makes the HP curve flat like a table.... Just the opposite of every other engine you'll ever see. The Tq peaks just over 300 (rear wheel ft/lbs) somewhere right above 3700 RPM and drops like a rock as soon as it hits it (just like the graph on the Digi' dash). The HP hits just shy of 210, but it is over 200hp from 2800RPM to over 5000RPM.
That was my baseline before any serious changes. With an aftermarket intake base, AS&M runners, a bigger TB and LT headers (the only thing I personally have left on my car) Most people report that the TQ peak climbs a bit, but the real advantage is that there is a level area from 3600 to (as much as) 4900 RPM. Thus the HP has a much higher peak number.

MrNuke

Daym!!

My vette with a K&N, otherwise bone stock with the Z51 (3.07 gears as yours) and the higher stall stock converter ran a best of 14.0-14.1@95-96mph years ago at it's best (although with 1.8 60foot times). My car was rated at 230hp from factory,but with that MPH of yours you are putting out almost 290hp.. You sure nobody has touched the engine before you got the car?

kopbet89c4

Man, I have no idea. The car dealer told me it was all stock. But I guess it isn't stock from what I have proven today. So basically the dealership lied or false advertised in MY own favor. Gotta love dealerships sometimes!!

P.S. The vette does NOT smoke at all so I'm guessing there is 0 - <1% of leakdown.

SBNova

What track did you run these numbers at?

Also, cranking compression doesnt relate to the rated or static compression ratio. The camshaft affects cranking pressure- so there is now way to tell by your psi numbers.

cv67

Just checked mine (89)awhile back-will have to get the numbers. Yours definitely look healthier!! I don't recall seeing anything near 200, for sure.

comp

CentralCoaster

My compression check showed 185-195, but seems everyone else here is 160 or so. There's so many factors, that you can't really compare between vettes.

Anyways, I never beat 14.4 at the track, although it was my first time out, so I might have been holding back a little.

cv67

Don't feel bad, CC. My first run at LACR was a 15.0@89.9 this summer

MaxLean

How much do you weigh? 3200# with you in it seems VERY light.

zelement

There are a lot of things here that are not right

1. I don't know any stock L98 even without a driver that can weight that little.

2. There is no way you are running 104mph in an auto stock L98.

3. A shift kit will not give you that kind of mph.

4. Your 1/4 time is possible with a stocker but the mph is off by at least 60hp.

kopbet89c4

1. I would have to take my car apart and "look" for mods. It may have been already "moded" without me knowing it.

2. All I really know about a shift kit is it makes the auto shift more crisp???

3. The car's weight varied a lot each time I weighed it, depending on how much gas was in it. Ahhh... No spare tire and no holder?? I just checked it...

4. I remember some 350Z 6 speed running 12.2@110 mph ?? He also claimed he was just about stock /w exhaust, intake, headers after I talked to him... lol

REDC4CORVETTE

My 86 stock L98 motor with 150 psi each cyl.
Trans go kit, vigalante 3000 stall, NItto dr 315-17 ran 13.80 95 mph 1.80 60'.
My 94 stock ran 13.70 stock 13.50 with nitto drag radials 2.0 60'.

scorp508

Oh yeah forgot this part. My 4+3 '87 went 13.89 @ 98.17. The stock dyno curve is included on this chart. The peaks were 211.2 hp and 315.1 ft/lb at the wheels.