ptc converter help

[dentmasters01]

I'm wondering if my conveter is too tight?
ptc 9-5-th-18-0
sl-sbp

car weighs 3830 w/driver. 129mph 1/4 trap last outing

transbrake = no problem obviously
footbrake= 5-6 lbs and its starts pushing through. ??

what other info do you need to really analize a conver?

 

[WSLN 6]

What rpm does it show at 0psi on the footbrake? What about at 6psi?

 

[dentmasters01]

I'll try and test tomorrow and report. weather permitting.

 

[V6RACER]

Best thing to do is call Dusty Bradford and discuss it with him. He'll get you set up right.

 

[dentmasters01]

Its a precision 70gtq. 0lb is achieved at about 2900-3000 rpm. 5lbs at 3400 rpm and its starting to push/spin the rear wheels.

 

[Dusty Bradford]

Should be very close, within a couple hundred rpm. Sounds like a rear brake issue if you can't hold more rpm without pushing. I can loosen it if you want but you need track data to see if it can stand to be loosened. Need to know rpm drop on the gear change and rpm in the traps. If your good with those readings I can loosen it to make it easier to hold with the brakes.

 

[dentmasters01]

ok, just went back through a couple data logs and if i shift at 6200 it falls to 5000 rpm. If i shift at 5900-6000 it still falls to 5000. all these numbers are +/- 50 rpm. The only trap speed I have is from bg. 20lb run was 123mph. 25lb run was 129mph.

 

[Dusty Bradford]

That's about where I like to see the rpm drop. What cam size?

I can loosen it a little without hurting performance, 200 rpm. It will help some but it still seems to be an issue with the brakes. Maybe glazed brake shoes....I always ran the cheapest brake shoe I could buy because they were the softest. It's something you have to watch if you do a burnout while holding the brakes. You want to use the softest pedal pressure you can get away with to keep from over heating the rear brakes.

 

[dentmasters01]

ok, I doubt it would be worth pulling out. I use a line lock for burn outs. I bled the crap out of the system until I had good clean fluid coming out. I may try a new set of brake pads though just to see if it helps.......I do have the s10 cylinders and use two large pads for each side.....

 

[Dusty Bradford]

ok, I doubt it would be worth pulling out. I use a line lock for burn outs. I bled the crap out of the system until I had good clean fluid coming out. I may try a new set of brake pads though just to see if it helps.......I do have the s10 cylinders and use two large pads for each side.....

Sounds like the brakes are set-up properly. Hard to say what could help the issue. I always had to launch my car with assistance from the e-brake but others didn't have to. If you try the new pads with no luck and want to try loosening the converter just let me know.

 

[dentmasters01]

Sounds like the brakes are set-up properly. Hard to say what could help the issue. I always had to launch my car with assistance from the e-brake but others didn't have to. If you try the new pads with no luck and want to try loosening the converter just let me know.

thanks for your insight. I'll try the new brakes and let you know if it helps. btw, do others report the 70 gtq hard to spool as well? with a 109 block and stock heads that is.....

 

[Dusty Bradford]

The 70 is generally easy to spool. I don't know what ecm your using but tune-up plays a large role in spooling as well. If the car is rich it will make spooling more difficult.

Most guys with 70's are using trans brakes though and not launching from the footbrake.

 

[bison]

I was holding 6-7psi on the street with mine and hooking it with no problem with an immediate flat foot . Car should run good with 15psi t-brake launches at the strip. Coupling very well up top too. I dont have the ds speed sensor in yet but when i do ill post the efficiency results. Looks like its going to be under 5% from what i see the tach doing:biggrin: .

 

[Louie L.]

Dont mess with the converter. Just noticed this was the vendors forum. Sent you a PM on how to fix the brakes.