I am having an annoying problem leaving off the brake...for the last six months I have been leaving off the button...on four occasions when I let go of the button the car hesitates and then launches...the first time it gave me a .184 light, then .180 then .179 and last time out a .157...

I race off the bottom with a 79 Monte going 6.50's in the 1/8 mile...it has a glide and my two step is set at 3200 rpm...

After the first time it happened we thought it might be a glitch...after the next two at the same event, back to back, we put in a new solonoid and button to be safe...after about 20 passes it happened again...

Any ideas on what it could be?...could it possibly be driver error on how I let go?...it is tough to race with this lurking...

When ever mine hesitates, (alcohol carb) I check the mixtures screws, squirters and float levels. If they are where I set them, I turn the mixture screws out 1/4 turn. The hesitation is most likely a lean condition in the transition from idle to wide open and most often is intermittent.

^^^ X2, also on alcohol.
Fuzzy, do you mat the throttle as the bulbs are dropping, or at full stage? And can you tell if the hesitation is a transition stumble from the engine, or a delay in the release of the TB? (If not sure, have a buddy video your launch from slightly behind, try to get a rear tire & the tree in the frame). If nothing else, the movement and/or audio may help determine if it is a stumble or not.

Which MSD ignition box?

I run 93 octane pump gas...I mat the throttle when fully staged...it definitely feels like a delay in the release of the trans brake, not a stumble...

I run an MSD 6AL2 box...the only curiosity I can think of is something I posted here about a while ago...when I go up on the two step my motor pops and bangs pretty loudly...I have had folks in the stands tell me it sounded like something was going to explode...I have gotten use to it at this point...

As to the hesitation, all I can think of at this point is maybe something is amiss inside the tranny?...I have never had any miss in the motor at idle or going down the track...

Remove the solenoid. Rock the brake valve, there should rock in it, slide it in and out with your finger tips.

Then get the transmission up to 200 degrees and do the same.

If it feels tight smooth it off with emery cloth in a drill.

Fuzzy,

That’s one reason why I got rid of my older MSD boxes and went to the 6AL Programmable is simply for the softer rev limiter. IMHO it made a huge difference.

Good luck and I would try what Mike suggested on the brake.

Your not using a long travel button are you?

Do you use a relay between the button and transbrake solenoid? I'm just wondering if maybe there might be some kind of feedback issue causing the popping? There is a guy that races with us and when we were still no box his car would pop really bad on the brake. He runs a toilet so I just figured it was a rich pop since his barrel valve was wide open. It can be an advantage because it would catch my attention when racing him and it would pop so loud I could feel it. LOL Caught me off guard the first couple times.

Not sure about the pause before release. I have heard of the valve having a burr and not moving freely at the time of release causing this to happen. Just some thoughts.

Curtis

What's your converter flash to? Wondering if the launch rpm is too low..

I use a mushroom button...

No relay that I know of...

My converter flashes to 3800 as I recall...been awhile since I checked...I have been told before I may be leaving at too low and rpm....hmmm...

My motor will be coming out soon for a freshen up...I have planned to take my converter back to FTI to be loosened up a bit for foot brake purposes...maybe I should take my tranny up there as well so they can go through it...both are theirs...

I had the same problem last year, got more prevalent the deeper I would go and I would have to chase a number in the box.

I found that the t-brake valve was bent, when it was cold, it was fine, but once it would build heat, it would stick. You could roll it on a flat surface and see the wobble. Also there was wear on one side of the valve. I know replace them every year. Cheap insurance as I know it sticking has cost me some money rounds.

After I rebuilt the trans, put it back in the car, first push of the button and it stuck and wouldn't release. Guess somehow I got the old valve and the new valve mixed up and put the old valve back in there. DUH!

quote:

Originally posted by fuzzy dice:

I run an MSD 6AL2 box...the only curiosity I can think of is something I posted here about a while ago...when I go up on the two step my motor pops and bangs pretty loudly...I have had folks in the stands tell me it sounded like something was going to explode...I have gotten use to it at this point...

You list the ignition as 6al-2. There are two different types. One has external dials to set the max / 2-step rpm values (6521) and the other is programmable with a laptop (6530).

If you have the programmable model consider doing this. Attach the Pink retard wire to the 2-step and retard the engine by as much as 10* when the 2-step is energized. This could possibly help the back firing problem.

Whenever I drop my launch rpm below 3500 I program timing retard when the 2-step is energized. The retard is removed at the same time the 2-step is released.

Using this method allows my engine to run smoother at WOT on 2-step when launching at rpms below 3500.

Thanks for the tip on the valve, Bill...I will mention this to FTI...

I do have the external model 6521, Mark...