dragster advice requested

[holeshotta]

i am new to dragsters coming over from fast 10.5 car. Bought hardtail racetech with 489 chevy on alcohol (1050 rupert) mechanical pump, merlin steel heads, eagle rods and pistons 12.5, 4.25 Callies crank. Hoosier 33.5/17/16 ties with 70 runs. 4.56 gear, NGK plugs gapped at .035. Struggling with consistency.

I am leaving at 4200, ( air shift at 6800) Tires at 5.5 psi and engine around 160 everytime. In good air running 5.05-5.09 ( 1500 ft, low humidity) and bad air fell off to 5.17 ( 70 % humidity and 3600 foot air) Mph 134.5-135.2. short times are varying from 1.12-1.16

are my ET's off? I am varying about .06 from run to run through the day. Previous owner ran same combo 5.03-5.05 everytime. I weigh about 25 lbs more than him.


Anyone have suggestions for tire pressure, launch rpm, timing, etc.


thanks in advance

[hammertime]

Timing should be 35-36 but how old are the tires ?

I assume your saying that it is moving around in the 1.12 to 1.16 in the same day its usually tire or converter. Launch less may help 4200-4400
I also assume you are stagging at 160 degrees ?

[holeshotta]

tires are a little over a year old. launching at 4200. stagging at 160 degrees.

[hammertime]

tires are a little over a year old. launching at 4200. stagging at 160 degrees.

Sorry I thought it said 4800 eyes failing me lol

I'd be betting on tires for sure.

[dparker]

tires are a little over a year old. launching at 4200. stagging at 160 degrees.

Sorry I thought it said 4800 eyes failing me lol

I'd be betting on tires for sure.

holeshotta what David is saying is probably the problem. I don't want you to take this personally but I was thinking some of your inconsistancy might be the way your staging and how quick you come up on the converter. I don't know if you know that for every inch you roll in after your prestage light comes on will change your 60ft times by .015. You have 7 inches of total roll out. so if your dragster goes in 2 inches deep it will make .03 difference in the 60ft and up to .05 difference in the 1/8. A dragster to me was alittle harder to stage just right than a door car. I think it maybe, its because it is lighter and rolls easier. Just a thought.

[holeshotta]

good point. I always try to repeat. i thank you for the thought

[dparker]

Your MPH isn't changing to much, so HP isn't varying to much at WOT. I think tires or loading up at starting line. If so probably to rich.

[shawnp]

I have to ask, are the tires chattering/skipping off the line. That is a lot of PSI for a hard tail car and your HP combo. I would think you would be between 4.5-5 PSI.

Hoosiers with only 70 runs are either tires that sat too long or someone told you wrong. We have gotten well over 300 runs on Hoosiers but average 250 runs or so before replacing.

I am thinking too much PSI is causing the tire to skip/chirp leaving he line. You are probably on the verge of bouncing the car on the leave. You may be too aggressive in the converter set up for hard tail car which will also cause this as well. A hard tail car is a very difficult combo to hit. I would swingarm it and forget it. Problem solved.

[3dracing]

We run the same tire on our 4-link. Are they C06 or Co7's? Our car did not like the Co6's, you really have to get after them in the burn-out.

[holeshotta]

they are C07's........ before i buy new, I will give less air a shot...... thanks

[dparker]

they are C07's........ before i buy new, I will give less air a shot...... thanks

On a hardtail the tires are your suspension. Also you need to be alittle rich for alcohol to work right, but if your way to rich it will slow way down under the same conditions that you have.
One more thing, I find that many new dragster owners start with thier legs to straight when they first set up their leg room on the dragster. If your legs aren't bent quite abit you can't keep from letting your foot come off WOT alittle bit at lauch. And the symptoms will be what your having also. My son when he first went to a dragster would run .07 off in the 1/4 with the 60ft .04 off, and I would ask him if he thought his foot came off alittle and he would always say no. Then one day when we were talking he said he was turning his right cheek up to put more pressure on the pedal. I reajusted his pedal and no more problems. A hard hitting dragster has alot of G force at take off.

[hammertime]

New C06's would still be my bet, but adjust to 4.5 like Shawn said. I replace tires yearly because sitting makes them go bad faster then racing more often then not.

All other post are good things to look at also