quote:

Originally posted by 1st_Gen:
I know you've already checked grounds but...friend/customer was having this problem after re-wiring. Almost exactly at 6500 rpms. Put it on a chassis dyno...rpm reads off of a plug wire, at 6400 the rpm sensor on the dyno went crazy,(meaning losing spark) along with sounding like it's on the rev limiter. Found a loose ground to the MSD...the nut was semi-tight. Ran like a champ after that. Like looking for a needle in a haystack sometimes.

quote:

Originally posted by Bucky:

quote:

Originally posted by 1st_Gen:
I know you've already checked grounds but...friend/customer was having this problem after re-wiring. Almost exactly at 6500 rpms. Put it on a chassis dyno...rpm reads off of a plug wire, at 6400 the rpm sensor on the dyno went crazy,(meaning losing spark) along with sounding like it's on the rev limiter. Found a loose ground to the MSD...the nut was semi-tight. Ran like a champ after that. Like looking for a needle in a haystack sometimes.

Sometimes the most efficient way to find the issue is to make wholesale changes, and walk backwards after one of those changes makes a difference.
In example, change the entire ignition. If that changes nothing, you know everything that you changed wasn't the issue. If it fixes the issue, you can leave it be, or start backing into what part of what you replaced is the issue. Sometimes that's possible and sometimes not. Hunting for that needle one at a time really stinks though.

I had an altered years ago that developed a miss right before the finish line. I spent almost a season changing things before I figured out that a body panel was moving with the buffeting wind and shorting out the back of a switch. Never would have thought it could move that much.

quote:

Originally posted by jimmyc:
Funny you say that about the ground to the msd box, I’m going tonight and run new power and ground wire to it. I’m going to put the ground on the battery it self not the chassis where it now. And putting the new ignition switch in it and run new wire for it also.

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Originally posted by rs72z:

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Originally posted by jimmyc:
Funny you say that about the ground to the msd box, I’m going tonight and run new power and ground wire to it. I’m going to put the ground on the battery it self not the chassis where it now. And putting the new ignition switch in it and run new wire for it also.

The msd box should be grounded to the battery or at very least to a lug on the chassis that has a ground cable from the battery also.

quote:

Originally posted by 27Keith:
I had a painful ignition switch that haunted me for about 6 weeks. Ran fine everywhere but on the track. Burnout was smooth and not missing or popping.(no load) Stage it, let go of button and it was crazy, shielded cable throughout, new box and coil, master switch, battery, alternator, took tach completely out of the car, tried it with no water pump running, new crank trigger pick up, probably more things I don't remember ! Half the class thought I was cheating running a stutter box, I was holding half a second just to try to stay up in points. Changed that Painfull ignition switch and all was better. I always carried a spare after that.

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Again for the clueless that think they know...when it ain't the valve springs, ignition or fuel, it's the converter!

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Originally posted by 27Keith:
Replace your power switch, not the main power in back of car but the power switch on your panel inside the car. Especially if it's a Painfull Wiring set up.

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Originally posted by markemark:
Your problem could be as simple as a bad ignition on toggle switch