madwolf

Last year, I picked up a 93 with a bad engine and I swapped a 94 engine in it. As soon as I got done with the install, I took it to the track and it did a best of:

2.006 60' (regular tires)
8.889 @ 79.19 1/8th
13.883 @ 98.40 MPH 1/4

That was on Oct 18th 2003

The car had a catback, cold air, 2400 stall, 3.23 gears, ls1 DS and my chip in it at the time.

Since then, I did a cam and headers. It dynoed 348 RWHP / 345 RWTQ in winter and 343/341 a few weeks ago. The horsepower and torque curves are pretty much ideal.

So I took it to the track again. Results:

2.020 60'
8.449 @ 85.67 MPH 1/8
13.012 @ 106.66 1/4

This was on 14 PSI slicks. No matter how well I heated them up, they never hooked better than 2.00 and everyone else seemed to have no problem hooking. (BTW, the car DID NOT spin or bog at all)

second run

2.018 60'
8.437 @ 85.67 MPH 1/8
13.012 @ 106.24 1/4

Third run was also 13.012!!! (maybe I should bracket race it? )

The "race" weight was 3605 #
Temperature 68*
Humidity 31%
Track elevation: 756 ft
Pressure in: 29.97

So I guess my question is... can anyone figure out why the car seemed to be down in power at the track by about 3 or so MPH before and after the cam?

I replaced the entire suspension and front brakes/knuckles/spindles. The only thing I can think of may be the tranny or the rear, but the tranny shows no signs of slipping whatsoever. It is the original tranny in this car which had 130K miles but shifts perfect. Also, I shifted it manually at the track ~ 6600-6700.

DarkHorse

Seems to be my problem too, I'm running low MPH and still trying to fix it.


Just sent you an email.

Fastbird93

What cam and headers are you running?? Is it possible that you're simply shifting it too high??

madwolf

I have a 233/239 and hooker LTs. The peak power of the cam is ~6200 and it stays pretty much there past 6200...so no, it is not too high. If I shift lower, the MPH will go down. My brother in law managed to get a 1.999 60' and a 13.2 with stock shift points (he let the car shift), but his MPH was only about 103.

I think I know what the problem is. After I bought the car, I discovered that it has been hit in the back on the driver side. There was some frame damage but it was close to the bumper... (past the wheels)
I guess since it's not hooking right on slicks, it is possible that the damage may be the cause. (but then why is it not showing up on the dyno?)

I think I'll just find a body with a 6 speed in it and swap over the engine with the front suspension...

WS Sick

That low tire pressure ups the rolling resistance quite a bit. I have ran on M/T ET streets and ran like 115, but when you switch over to drag radials I picked up a few mph. this may be your difference. But of course when I run the E.T. Streets my 60 foot time is about 4 tenths better...lol

atljar

What kind of stall is in it?

Ive seen several of them "baloon" internally and still run fine. More common on a converter from companies like transStar or SLP, who just take a stock stall and restall it. Not only are you stuck with a stock STR, the STR doesnt ever hit like it should getting you a good launch. Personally i think 2400 is a tad too low too, even with a smaller cam like (i think i remember seeing) you have.

That and in combo of only 323s, could be lots of your launching troubles. Why not get some gear in her

madwolf

It's a 2400 SLP stall. It does look 100% like the stock stall only different color. Do you really think a 2800-3200 VIG would make that much of a difference? I think I'll just go with a 6 speed anyway... I've had one before and it sure was a heck of a lot more fun that this auto is.

As for the MTs, I tried them at 16 PSI and they did not hook as well as they did at 14. I also tried running on stock tires and the 60' was like 2.2 but the MPH was about the same.

WS Sick

Inmy old 93 the first converter I had was a TCI 2500 lock-up, the best 60 foot I could manage with it was a 1.89, I switched to a vigilante and the first time I launched with the same car, no other changes was a 1.74!!! I also gained from a 13.4 to a 12.8 !!!

madwolf

Weird.... you could not have improved your ET by 0.6 seconds from just a 0.15 gain in the 60'. Does a converter have any other effect other than a better 60 by placing you deeper in your powerband? Would the higher STR improve MPH?

atljar

Yes a Vig or Yank will do wonders. STR is going to play just as an important roll as the stall speed. You should ideally match both to your power curve if going all out, but concessions have to be made in a street car. STR isnt one of them, as it really has little ill effects on driving, just a much more expensive convertor. I know the off the shelf vigilantes are 2.5 STR, i think yanks are right there with them. Yanks customer service leaves much to be desired however.

The thing if you go 6 speed... you are going to need steeper rear gears. Expect to put in a 9 inch or 12 bolt, and still need a clutch/tranny/hydrolics/pedal etc etc. The swap is fun, but will cost a WHOLE WHOLE lot more than a $700 vig.

atljar

On the STR helping power, yes. Havent really explaned this...so here we go....


STR = Stall Torque Ratio

Take the stall speed (lets say 3000 rpms). At that RPM, find your torque readings, and multiply that by the STR number. At that given RPM, thats how much torque the stall will put down (reason you see the huge dyno spikes with good stalls).

So if you have a 1:1 or close to it like a stock convertor, you will be leaving the line with about 330 (?) RWTQ. Put a vig in there and you are suddenly leaving with over 800 RWTQ. That will shake things up a bit

madwolf

If I swap, I will swap this engine and the k-member with the suspension on a 6 speed body. It will be easier for me to do this since I've changed to LS1 brakes and replaced all 4 ball joints on this k-member (also did springs and shocks), plus I won't need a hoist. I am aware of the gears and 12 bolt though.

I am still confused about a how a different stall could improve the MPH. The STR only works on the launch.. it does not affect the run other than that. So do you think the it will improve the MPH by pretty much a bigger kick in the butt?

atljar

Yes, slingshot effect

Apples to oranges comparison here, but dropping the clutch at 4k in my car, compared to an all out 6k launch, i gained about 2.5 mph consistantly, as well as better 60's.

madwolf

OK, you answered my question before I replied. I might try a 3200 VIG then...

At the same time though, shouldn't I be able to pull a better than 1.999 60' on slicks with a 2400 SLP and 3.23 gears?

atljar

Maybe a tad, but i would be very suprised to see anything sub 1.90s, where as a vig car i would expect mid 1.7s assuming you have traction.