'82 Berlinetta, 3450* lbs going down the track, 2000 SS LS1/T56, LS6 intake; Hawks 1-3/4"->2-1/2" LT's w/duals dumped at the axle (for now); 9" w/Strange nodular case, 31 spline True Trac, Moser axles, 4.11 Richmond gears, Daytona pinion support and bearings, 3"x.083" DOM driveshaft with 1350 yokes, ladder bar conversion eliminating torque arm, LCARB's, SFC's, poly everything; 9.50-26x15 Hoosier Quick Time Pro DOT slicks (pressure TBD, thinking 12-13).

With the 10-bolt, it ran a best of 13.54 @104.6 with 2.09 60' spinning the tires with 16 psi in them. I expect better traction now (didn't have LCARB's then).

I've heard 4000 RPMs, seems a bit high. 3000? 3500? I do know it will bog horribly at 2000.

What say you?

*Weight with full tank of gas and 10-bolt - with half tank of gas and 9", I expect it to be about the same.

 

3750

 

It only gives me 100 RPM increments. . .

 

continue raising it until it stops bogging, then keep raising it until you lose traction, then back it down

 

I'll get 6 time trials tomorrow. Hopefully that will be enough to figure that out.

 

I've seen a few take them to 5k to keep them from bogging.

 

I hope it isn't that high. Based on the few runs I got in before, 4k will probably be more than enough.

 

Is your motor stock with the LS6 intake?
You might have to take it over 4K. I thought that you had cam in there.

what is your ET/MPH at sea level?

 

Agreed this is the best plan but as a guessing man I'm gonna say 5K

Mine like 5500 RPM but it still bogged a tiny bit. 3.73's on a stick though is not ideal for launching but its a street machine so I lived with it.

As a further guessing man Im going to say 12.7 with a 1.72 60' ends up your best pass but I'd love to be proven wrong and see you break out of my guess

Happy dumps

 

Well, DA was about 9500 today, so no 12's.

I started at 3500, bogged pretty bad but still spun. Great. Figured bog was worse than spin, so I raised it to 3600 and lowered tire pressure a psi. Better, but still bogged, so repeat process for next pass. 60' is improving, so by the 4th pass I was at 3800 and 11 psi, so pretty much decided to leave it like that.

We had a 4 hour rain delay, by the time we got running again the weather station said DA was down, but humidity was sky high. I managed to win and come back, humidity started going down along with temp, so we were at about 8000' DA when we started going round robin. I was running the slicks at 10 psi, still some spin and slight bog, but the thing was just repeating. I ended up losing both classes I was running in by break-out, but I wasn't the only one breaking out - atmospheric conditions can be pretty weird at this track.

So, bests from today:
ET - 13.485 (bad news is I dialed 13.54 - really bad news is it was against the points leader who only broke out by .028)
MPH - 104.06 (not the same run)
Best 60' - 2.016 (was in the 2.05 range during the heat of the day)
Best RT - .013 (also .006 off my dial that run, for a .019 package)

Clutch seemed happy. 2-step worked flawlessly. Can't complain for first time out in a car.

 

Those 60's are in dire need of bite! Whats your pinion angle set to?

 

I set it at zero since the ladder bars don't give. But, now that I think about it, it is lifting the rear at launch, which pulls the angle positive. I'll try giving it some negative before the next race.

 

I had my nephew video my car closely from the rear and side during five or six launches. Playing back at slo-mo you could clearly see what was going on so it made suspension adjustments easy. I went from high 1.9 and 1.8 60's to consistent 1.6x after that. Im sure some more angle will help. Mine seems best at -3 but Im still a TQA car so a bit different. Anyways hope the thought might improve the cause

 

I was concerned about putting too much negative in for "normal" driving, and changing the angle isn't all that easy (although it looks like it should be).

 

I drive daily on the street that way. Havent noticed any negatives although its probably a little hard on the u-joints I really dont care as I have a guaranteed for life drive shaft from PST

 

what size slicks? those 60' are horrible....is track prep that bad or are those ladder bars the issue? How old are the slicks and what pressure are you running?

 

9.50-26x14 Hoosier Quick Time Pro DOT's, ran as low as 10 psi. Track prep was great, I was dumping the clutch, not feathering it at all. I think it's the ladder bars not set up correctly yet. It was spinning, but I can't complain about the ET consistency.



You may convince me to go back to a torque arm. I'll try more negative pinion angle first.

 

10psi seems rather low as well, I'm normally in the 12.5-13.5 range on my setup. Do you have any side pics from the launch? you're looking for the slicks to wrinkle in the down and forward area from the rim. Let me dig up a pic here.....

only pic I could find on this computer:

 

wow the rear of the car shoots straight up in the air at the launch, i'm guessing that's a side effect of the little ladder bar setup. i'm also thinking that you might need more negative pinion angle and possibly more psi in the tires.

 

I ran them at 16 psi on Berlinetta #1, which isn't going to hit them as hard. I started out at 14 psi, even with the bog they spun. The best 60' came with 10 psi. But, I never tried 3800 RPM launch with 14 psi (need a good T&T day to test that stuff out).

The rear does jump right up. A longer bar may better balance that out.

My son got some stills of the launch that does show the wrinkle (the video was taken by my wife). Not sure if he caught it at the hit, or after it stopped spinning. I need to get them copied so I can post them.

At least the True Trac didn't give me any trouble. I've had my fill of issues with clutch posi's.

 

Not trying to argue the point, but don't forget this is at 5800' elevation, DA was about 8000' at the time of the best run.

 

Just realized you guys are running autos. Even with a tranny brake, it won't hit the tires as hard as a stick does.

Some of the fast stick cars (low-10's, 9's) let the tires spin just a touch at the hit. Others just seem to dead hook.