So I have been chasing a problem on my car and haven't been able to test enough to find it. Points races and Covid stoppage has me behind.

At around 7100-7200 my car will act just like it's on a rev limiter. I have to shift at 6900 and can't run 1/4 mile. Has anyone ever seen an ignition box act like that.

Things I have done:
New crank trigger pick up.
New distributor.
Shimmed springs first then changed springs.
Carb is different but have o2 data anyway.
I use a 3 step and have pulled the high side chip.
Made sure trigger wires are away from anything.

I was going to test Friday but they cancelled. I plan on pulling the three set plug out of the box. Other than that I will change the ignition as a last resort.

Did you pull the chip from the 3 step or unplug the 3 step from the 7al2?

I had a 3 step that as long as it was plugged in, didn’t matter whether you had a high side chip in it or not, would activate about 7k. New 3 step box fixed it.

quote:

Originally posted by BJs Wild Ride:
Did you pull the chip from the 3 step or unplug the 3 step from the 7al2?

I had a 3 step that as long as it was plugged in, didn’t matter whether you had a high side chip in it or not, would activate about 7k. New 3 step box fixed it.

No as I said I just pulled the chip. Pulling the 3step was next but they cancelled TNT until next weekend. I will try that.

If you are using a stand-alone toggle switch for ignition ON try replacing the switch. If you are using a toggle switch panel move the Ignition ON to a different switch if available. If not available interchange with another output like the fan.

That type problem has been posted several times here.

quote:

Originally posted by markemark:
If you are using a stand-alone toggle switch for ignition ON try replacing the switch. If you are using a toggle switch panel move the Ignition ON to a different switch if available. If not available interchange with another output like the fan.

That type problem has been posted several times here.

I will look into that sorry I wasted your time.

how old are the valve springs?


Joe

quote:

Originally posted by CURTIS REED:
sorry I wasted your time.

it wasn’t meant the way you interpreted it

quote:

Originally posted by sr4440:
how old are the valve springs?


Joe

10 runs

quote:

Originally posted by markemark:

quote:

Originally posted by CURTIS REED:
sorry I wasted your time.

it wasn’t meant the way you interpreted it

Sorry man. Sometimes when you having a day you read things the way you feel.

I would try new plugs and plug wires and also double check rotor phasing. May tighten up plug gap a little. Also check all your grounds. Check your alternator and battery to make sure you have enough power to fire the box at RPM.

I have a 7AL-2 box you can swap out and try if you want. When my box went bad it would bang and pop real bad one run and run a 5.50 or so. Next pass clean and run 5.0X. But it was doing it most all RPM range. New box ran perfect. I now have two good spares and you are welcome to try one.

My son was chasing a high gear miss for a while. He could not hear it at first but it was showing up on his data graph.
Tried new plugs then wires. New cap and rotor all of the standard stuff that can cause a miss.
Went so far as to install a noise cap on the main power wires.
The miss had became worse and was quite audible going down track in high gear.
We pulled the body panels off and started checking the wiring.
He found the switch on lead to the MSD box had came loose with in the crimp connection.
You could pull on the wire and see it move in the connector. The wire would not pull out but it was loose.
New connector and a better crimp miss is gone.
Good grounds and good wire connections.
A must!
Hope you find it.

quote:

Originally posted by Curly1:
Check your alternator and battery to make sure you have enough power to fire the box at RPM.

Was doing some troubleshooting last weekend and looked up the amperage draw. For a 7AL3 it said 1 amp per 1000 RPM.

curtis strange things happen,with all that you have tested i would have to reverse the trigger wires just so that i knew.i always forget which way is which but you can look it up

I once had a hairline crack near an intake bolt that caused a high RPM miss.

Standard miss-chasing steps for me are remove all chips, disconnect the tach. Then other things that have been suggested such as plugs, wires, cap, rotor, trigger pickup.

It usually isn’t the ignition system at all, in my experience.

quote:

Originally posted by rusty:
curtis strange things happen,with all that you have tested i would have to reverse the trigger wires just so that i knew.i always forget which way is which but you can look it up

An analog box such as the 7AL-2 should have the pickup wired whichever way gives the least timing advance.

I had a 7AL2 box go bad and would miss at higher rpm. Tach was also erratic when it missed.
Borrowed a friends identical box and there was no miss, tach worked normal

Sent box to MSD...they tested it said it was good.

Put back in car and same issues were still there. Put my friends box back in at the track, issues gone...

Replaced box with a digital 6

Bruce I appreciate the offer of the box. Who knows I might take you up on that. At this point I’m going to try removing the 3 step completely and go from there. This isn’t a miss, it is full on just like you’re on the rev limiter.

I appreciate the replies and ideas though.

quote:

Originally posted by CURTIS REED:
Bruce I appreciate the offer of the box. Who knows I might take you up on that. .

Just let me know.

quote:

Originally posted by CURTIS REED:
Bruce I appreciate the offer of the box. Who knows I might take you up on that. At this point I’m going to try removing the 3 step completely and go from there. This isn’t a miss, it is full on just like you’re on the rev limiter.

I appreciate the replies and ideas though.

I had a fluttering power valve do that once. Acted like a 5500 rpm chip was in it. Spent half a season changing ignition components.

We had changed the cam, and with the new cam it didn’t make enough vacuum to hold a 6.5 power valve open.

Don’t overlook anything, is what I’m saying.

Good point not to get stuck. While Id Put a couple bucks on a bad 3 step in your case, I had an interesting deal last night.

I took out a newish combo last night. Had went on the converter just fine at home. 1st time run it was a little warm when I staged. Went 3100 on the brake (I had actually forgot to turn the 2 step back on in the grid) and stayed at exactly 3100 for a couple seconds after brake release.

Sounded and felt just like an rpm limiter. Looked like it in the data too. Matter of fact it seemed identical to a bad ignition box I ended up with about 10 years ago.

Turned out to be a fuel issue.