Engine turns off at 8250

Hi Guys,
This has me purplexed.
I made a couple runs this past weekend.
Items are ALL NEW MSD: Mag 44 power head, Mag 44 points box with rev limiter, MSD two step and MSD Mag 44 coil.

On each pass the engine would "turn off" at 8250 RPM.
No sputter or skip, it would just go dead.
Once the RPM was below 8250 (I lifted) it would come back to life.
I'm sending the boxes to Dave Leahy but I'm not sure what it could be.
It runs flawless up to that point.
I changed RPM chips, etc, everything works fine.

Anyone have any ideas?
grounds maybe; even though everything is grounded to the battery????

Thanks in advance.
Frank

 

if you are running a crank trigger look at it.this same thing happened to a guy I know and it was the trigger pick up

 

Thats the first thing that came to my mind, had the SAME thing happen to me at the ROCK last fall. Actually got air under the REAR tires when the motor started bucking (going on-off-on)!!UGLY

 

Hard to believe, but a crank trigger too close can cause something like this.

 

Thanks for the info guys.
Unfortunately NO crank trigger.

Keep the ideas coming.
It's much appreciated.

Thanks
Frank

 

Are you using MSD chips? Autometer chips will plug in but they have different resistance values.

 

Also, if you are using the rpm selector that is the msd dial type,ex. 8000 to 8800 in 200 rpm steps, you cannot make the connector wire longer by splicing in longer wires to get it to reach a more accesible location. Doing so will change the way the selector reads rpm limits, in other words funny shit will happen to your ignition. Don't ask me how I know this, I chased a problem all around my car before a call to MSD found the problem.

 

Change the RPM Chip 1st to see if that eliminates the problem.

 

It has a 9000 high side and a 4200 starting line activated by the transbrake (two step).
I pulled the 2 step and put a 3000 high side, it worked fine (testing in the pits). I swapped chips and it all seemed fine.

Like I said what is weird is that it doesn't miss, skip or stutter like it's hitting a chip, it just quits, it goes dead silent. I roll my foot off the throttle and roll back into it and it comes back to life, of course at a lesser RPM.
No wire splices.

Thank you for the ideas keep them coming.
Frank

 

One thing I forgot to ask;
Could it be TOO fat?

The plugs are only showing color about one third around the base.

 

With this statement i'd say you are lean. By rolling off the throttle you are cutting back the amount of air getting to the engine there by allowing the fuel/air mixture to get back to a burnable point.

If this is a new "upgrade" to your ignition system. You might be suprised how much more fuel you will need than you used to run.

i say this because i've done it. We replaced everything at a race one time chased our tails for two days. I finally told my Old man i'm upping the jets/pills 8 steps he told me i was crazy but the motor came to life and went right back to where the RPM's should have been.

Just my .02
James in Vegas.

 

Stick an MSD tester on there and run it through the RPM range.

 

we had similar problems with the chips. they go bad! also, a 9000 chip will not just start interrupting the ignition at 9000. we have had some that would be up to 600 rpms early. either take out the chip, or put a 10,000 in it and try it.just my 2 cents

 

I knew a mudracer that had the fuel outlet on the front of the fuel tank. He would step on it and get about half way through the pit and the engine would go silent.

 

shutting down

would not hurt to check the fuel tank vent size too..

 

Does the car have a data recorder? Check fuel pressures especially around the point where it dies? That would rule out fuel related issues. We had a problem where our TAFC was dieing about a hundred feet off the starting line. Sometimes it would come back on, other times it just stayed off. We looked everything over twice without finding a problem. Finally I took the kill switch off the car complete with all the wiring. By looking at it in the light of day and being able to go over it with a magnifying glass I found a spot where the insulation had worn through and it was making contact with the chassis. But for some reason it only touched the frame during certain times when the chassis flexed. I now know to replace kill switch wiring periodically just like you change your coil wire. Dave Germain

 

I had the same symptoms as you Dave and after an extensive diagnostic procedure.I found the fuel pump inlet hose was getting sucked closed on the inside only at the hit.This was before I had a data logger,now it would be easy to find.Those things are worth there weight in gold when a weird demon shows its ugly face.