converter help
 

I have a 8 inch coan converter 5000 stall, in a 81 camaro with a 383, bracket car.(set up like a stock eliminator car)
When i foot brake the car it tries to pull me thru the lights at 2200 to 2300, i have my 2 step set at 2000. I have a buddy with a 68 chevelle with a junk converter drum brakes and he can launch his car at 3500.
What do the stock guys launch at ?
Come on stock and superstock racers you guys are the best at getting the most out of your combos.
Thanks Mike

Re: converter help
 

Is it sliding tires or brakes not holding?

Re: converter help
 

Terry brakes arent holding, the car keeps moving the more i bring it up on the converter. BTW if thats your corvette in the pics.... very nice car. Thanks Mike

Re: converter help
 

Mike, do you know what RPM the converter actually flashes to?

Do you know how much slippage you have?

What is your average ET and MPH?

Describe the car, weight, gears, tires, brakes, transmission, engine, etc. It help to know what we're looking at.

Re: converter help
 

Alan i dont know what it flashes too and i dont know slippage.
1.52 60 foot 11.04 @ 124 best et 4.10 gears 28x10.5 slicks
QA1 coil conversion on front, split caltrac leafsprings and caltrac bars rear, competition engineering shocks on the rear, im going to caltrac shocks over the winter.
Stock disc front and drums rear
TH350 for trans
383 stroker
victor jr intake( ported to match heads)
950 hp carb from pro systems
eagle rotating assy 12.1 srp pistons
Cast iron dart sportsman 2 heads 2.05 1.60 valves ( ported)
all roller valve train
Ok i know you guys get alot more out of less so dont flame me to hard:eek:

Re: converter help
 

4.10 gears need to go first off,12-1 comp I'm pretty sure you are'nt cruisin much


I know you check flash when launching car @ track when you leave line watch where tach goes to as soon as hit the gas,it will usaully kinda hover there and then come back a few hundred rpm and then start climbing from there.

On slippage figure using formula, MPH X gear ratio X 336 divided by tire height= RPM
using info you gave if your converter had 0% slippage you would turn 6100 @ finish line.
figure % difference in 6100 and what you are crossing trap @ and that is % of slip you have.
Lowering rear gear will help reduce slippage @ finish line,but will also lose some stall on launch.

I'm bored while taking a break or would not even responded to automatic questionLOL.
PS i borrowed 4500 converter on time could hold brakes and bring up rpm keep easing down on throttle and could go over 6000 without moving car(junk) bought new one that flash 4100 about 2500 was as far as could hold it,worked on brakes got to 32-3300.

Mike Taylor 3601

Re: converter help
 

I'm guessing you have drum brakes on rear ? You can measure the brake drum size and some careful measuring might get you some larger brakes , like from a truck or van. Buying 2 sets of shoes and installing the long ones only will help some, it's old bracket racing stuff. A band aid, if you will, but if you are serious, get disc's for the rear. It will make a big difference.
Personally, I use a brake pressure gauge, to know where it leaves best at, consistently. Some dont like them, but, it does for me.

Re: converter help
 

You should always know what your flash stall speed is, and how much slippage you have, it helps diagnose any problems you may have.

I'd expect a converter with 5000 flash speed to have about 3000 RPM "free stall", that's what you should be able to hold when you're on the starting line.

In order to make a torque converter "stall", you need torque from the engine, and resistance from the brakes and tires.

You need to make sure your engine is running well enough to make enough torque to create the stall speed you need. I've seen guys who have their engine running good at 5000 RPM, but it runs like crap at 2000 RPM, they think "it does not matter because I have 5000 RPM stall." But that is not true.

You may need to work on your brakes. You need soft pads and shoes on a drag car, especially with stock brakes, not the metallic materials, as you do not get them hot enough to work on the starting line.

Re: converter help
 

Alan what you are saying is textbook for my car. With the trans brake I could get to 5000 and launch. But with the foot brake I can only get a little over 3000 against the brakes.
When I flash the converter (static in 3rd with the brakes locked as hard as I can push) it goes to 5000 (on the datalogger)

Re: converter help
 

Playback tach is a great investment. I could not tell you what the converter flashes to, or where the needle sweeps during a shift during a pass, but I sure can show you back in the pits. BTW a high stall with a low break away RPM IMHO is the sign of a quality converter. (assuming it still hit's the required flash RPM) A cheap stall will slip a bunch and give you a higher easy stage RPM. (like you're pal's)

A xxxx stall converter is dependant on so many things. (well, everything) I had a 4500 stall custom built for my first personal performance engine in the mid 90's, a 331 Chev. I could footbrake it to about 3800, but not reliably. That same converter I could footbrake at 4250, but it was a very mild 350. That same converter would flash to 5600 behind my first 408 small block.

A trans brake would eliminate your issue and give you some starting line tuning. I guarantee you could benefit from additional rear gear.