Fluttering popping and cracking

May 03, 2018, 10:49 AM

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.

May 03, 2018, 11:13 AM

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.

May 03, 2018, 02:58 PM

1st_Gen

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.

Yep, I'm pretty sure he thought he had checked the grounds already.

May 03, 2018, 03:01 PM

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.

May 03, 2018, 04:07 PM

rs72z

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.

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.

May 03, 2018, 04:51 PM

markemark

quote:
Originally posted by rs72z:
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.

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.

Agreed. Along with the positive cable to battery.

May 03, 2018, 07:45 PM

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.

May 03, 2018, 08:20 PM

Curly1

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.

I had a similar problem years ago. Car would start and run good around pits etc but when I launched it would go crazy. Turned out to be a loose ignition wire.

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May 03, 2018, 10:34 PM

markemark

At this point in the component replacement, after the OP finishes replacing the control switches, relays and wiring I’m confident the Fluttering popping and cracking problem will be resolved.

He has done an exceptional job of documenting the systematic replacement of all electrical ignition components and eliminating the mechanical and fuel systems.

I’ve bookmarked this tread because it serves as a great guide to what one could look at when trying to solve a suspected ignition type problem.

May 04, 2018, 07:45 PM

jimmyc

Happy to report its fixed. Made 3 passes tonight and ran perfect. Ignition switch was the culprit. This is one that will stick with me in the memory bank. $15 part cost me a lot of lessons. I really appreciate all the info and offerings of things to check and try.

May 04, 2018, 08:23 PM

Cashflow

Hooray!

May 04, 2018, 08:31 PM

markemark

This is good news and happy to hear you have solved the problem. Good Work !!!

On this thread Page 2 of my first post I made reference to the Ignition ON toggle switch as possibly being the cause.

I used Grid to verify my Ignition ON toggle switch was working properly even after I replaced it with a remote switch early in my component replacement in an attempt to solve my ignition missing problem.

May 04, 2018, 09:05 PM

FastLane

quote:

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

May 04, 2018, 09:14 PM

1320racer

what part of that statement don't you understand moron?

It was the ignition and the OP stated he checked/replaced ALL components of the ignition which he obviously hadn't.

May 04, 2018, 09:45 PM

Curly1

Good to hear it is fixed.