Just got back from the track tonight...er, last night and the car's still running consitant. Consistantly bad that is . 60's are no where near what I want them to be and my driving is also pretty crappy. Car's not running consistant (ET wise) trap seems to be ok, still needs some carb tuning she still likes to run really rich but other than that I'd like to know what you guys think is causeing this car not to 60 better (other than my driving). She's leaving straight now thanks to the drag bags so it's kinda weird. Also kind of curious on why my 1/8th mile trap seems low compared to my 1/4 mile trap.

2950lb race weight
Suspension Consists of
90/10 up front, 50/50s in the rear, moroso trick springs up front, v6 springs in the rear. Spohn torque arm at -4ish lol, lakewood panhard bar/lower control arms and Drag bags (5 psi driver, 25 passenger) and 26x11.5x15 Hoosier QTPs. Pump gas (91 oct) n/a small block through a T-5 & 10 bolt

Times are as follows from worst to best left to right
R/T-.249 R/T-.118 R/T-.069 R/T-.225
I1-1.731 I1-1.699 I1-1.694 I1-1.667
I2-xxxxx I2-4.867 I2-4.790 I2-4.748
I3-7.445 I3-7.410 I3-7.294 I3-7.246
MPH-101.994 MPH-99.269 MPH-99.269 MPH-100.069
I4-xxxxx I4-9.757 I4-9.442 I4-9.375
ET-11.367 ET-12.104 ET-11.221 ET-11.146
MPH128.741 MPH-95.691 MPH-128.744 MPH-129.196

2nd slip i donno if i let off before or after the 1000 ft mark
Anyways so im launching the thing at about 4500rpm any less she's a dog (more than already) any more and she just blows the tires like crazy. Played with tire pressure from 20-8 psi (cold) those are closest to probably 10psi cold. I'm thinking since I dont have LCA relocation brackets, since the tire's only 26" tall and theres so little air pressure in it that the arm angle is making it rotate up or something . Thoughts on anything guys would be appreciated

 

how bad is it spinning at the line? I would say go to taller tires for more of a contact patch.

 

Ack! Timeslip format is terrible. Break the run down into sections to see where the car picks up or slows down. Lets see if we can make that more viewable. and eliminate the first run since it doesn't have complete times. It's fast enough for comparrison but without all the incremental times, breakdown is limited. I also see run 2 was bad but we can still show the times.

feet -- 2nd ---- 3rd ---- 4th
60 --- 1.699 -- 1.694 -- 1.667
330 -- 4.867 -- 4.790 -- 4.748
660 -- 7.410 -- 7.294 -- 7.246
1000 - 9.757 -- 9.442 -- 9.375
1320 - 12.104 - 11.221 - 11.146

Now to do breakdowns of each run. You list each run as incremental time. 60', how long it took to go from the 60' to the 330' etc

----------- 2nd ---- 3rd --- 4th
60' -------- 1.699 - 1.694 - 1.667
60-330 ---- 3.168 - 3.096 - 3.081
330-660 --- 2.543 - 2.504 - 2.498
660-1000 -- 2.347 - 2.148 - 2.129
1000-1320 - 2.347 - 1.779 - 1.771

You can still use the first run by skipping the missed time. Instead of how long it took to go from 60' to 330' just redo all the calculations to go from 60' to 660'. Everything happens in the first 1/8 mile. Traction, shifting etc all contribute to the 1/8 mile times. The last 1/8 mile, you should be in high gear and doing a brute HP pull to the finish. Any difference in times there are more related to the weather, wind etc. Jetting and valve lash if a solid cam will also show up in the last 1/8 mile.

Now from looking at that breakdown, we can see that run 2 was bad all the way down the track but we're just using those numbers to see any changes. Between run 3 and 4 there are 2 big differences. The 60' time on run 4 is much better and the time it took to go from the 1/8 mile to the 1000' is much better. All the other times are close enough. Except for the slower 60' time in run 3, the first 1/8 mile is almost identical to run 4. 60' time is all traction so you just didn't have as much on run 3 but what did you do different on run 4 between the 1/8 and 1000' mark to drop the ET? Assuming you're not geared for optimal 1/4 mile performance, my guess is that you shifted into high gear after the 1/8 mile mark either on the 3rd or 4th run. For all vehicles, the 1000' to 1320' should have very little variation. By the time you've reached the 1000' mark, your ET is carved in stone. If there's a big variation in time, you were probably hard on the brakes at the finish or there's some major problem with the car/engine/driveline.

I can't offer any advice on how to set up the carb, timing, tire pressure, suspension, etc since those are all tuning aids. Each car reacts differently to changes. It could be something like needing notched floats in the carb, bigger jets or squirters. Maybe the valve springs are worn out and don't have enough spring pressure. Maybe the fuel filter is dirty. Maybe a gust of wind came up. It could be any number of things.

If your LCA are not parallel to the ground or down slightly in the rear, get some relocation brackets. Change you pinion angle to 2-3* down.

Your MPH is your indication of HP no matter what ET you run. 128.741, 128.744, 129.196 is all pretty close. That's less than .5 MPH between 3 runs. Nothing wrong with that. When tuning, tune to get the best MPH.

 

if you were at the psca in fontana yesterday, the air was really good later in the day.

what rear gear is in the car? your running mph that is typically seen with much lower et's. id say more gear and taller tires would help with the et's.

the way stephan posted the breakdowns it looks like you take a long time to go from the 60 to 330 mark.

 

not enough gear

 

I'm shifting at 6500 and crossing the traps at like 61-6200. 26" tall tire, 3.73 gear. Pretty sure im goin into 4th (1:1) after the 1000 foot mark, not 100 percent sure on that tho.

 

No i was up at sac for grudge night

 

So saying the tire grows 1/2" for a 28 (28.5)x10 tire going through at 6500 says I need a 4.26 gear (4.30s) i guess which would over rev to 6550rpm. Or id get a 29 (29.5)x9 tire going through at the same rpm and it recommends a 4.41 (4.56) which would over rev to 6711 rpm. Which tire would you choose? Better yet which would put a bigger footprint down at the same psi?

Honestly the only reason i'm still running a 3.73 gear is because i'm still running a 7 1/2" 10 bolt and don't want to throw any more money into a rear I know has already outlived its recommended life span. Same goes with relocation brackets that i have to weld in.

What do you guys think of running a 29 (29.5) tire with the 3.73s and crossing the traps in 3rd (1.34)? Would get rid of 1 shift which should help ET but it would over rev to 7356 Good alternative? Could I fit an even taller tire underneath with out any fooling around with the wheel well? From what ive read 29/.5 is right around as big as you can get.
Thoughts?

 

No kidding...running that kind of power through a T5 & 10-bolt for this long is amazing..LOL. I did a dump at 4000 with my T56 & 10-bolt & thought I was going to have to walk home..