Sure sounds fuel or converter related

Do you have the msd starter saver if so unhook it try that , same problem once replaced allot of parts, thought to myself lets try a pass without it and bingo ran fine

Have you tried an MSD Ignition tester to isolate the ignition system? I would hook up the tester and simulate a run and let it rip up to about 10K. If it tests clean, you have pretty much ruled out the ignition system (unless it is vibration related).

Engine miss is NOT the converter, rear end, transmission, tire pressure, what kind of tow truck you have or what color the car is painted.

Has nothing to do with an ENGINE miss. Stay with me here people and listen up.


The first place to look for an ENGINE miss is at the ENGINE. It is an ignition issue, fuel problem, or wiring issue. It takes Spark, fuel and air to fire and that is where you start looking to find your issue.



1. Change out the ignition box. Quick cheap and easy. Just borrow one from someone for a pass or two. Also for the test I would eliminate as many other electrical components, RPM chips, shifter modules, Two Steps etc as possible to help you determine electrical or fuel.

2. Change out carb with a completely different carb. Yes you have been through the carb but there may be a chip or trash blocking one of the orifices inside. Could be a float that is bad, that limits the range of adjustment and limits the fuel flow at high RPM. Could be any number of simple things but trying a different known good carb will tell you a lot of things.

Those two things are quick, cheap and easy and will help you narrow it down. Once you change out those two things it will give you a good idea what is going on. Now if by change changing those two components does not resolve the issue then you can start checking other things like broken valve spring, fuel pressure etc. but check the most obvious and simple things first. Ignition box and carb.

I have seen and verified with my data logger a "Good" ignition box missing on high end. So simple to change it out and verify or eliminate that as an issue. Same with a carb.

quote:

Originally posted by jimmyc:
Is fluttering and I can’t seem to find the cause.

Everyone's fluttering could be different. If it's popping, it's lean. If it's missing, it's ignition (anything from the cam gear to the electrode). If it's poor upper performance it could be springs, dumping fuel, timing, ignition failure or set wrong.

IMHO

MSD Ignition tester.

I have one and while they are good to verify your shift module, two step, RPM chips etc. They are of little if any help to tell you if ignition box is bad. I have had several boxes fail in the past and they all check perfect with tester.

Also MSD says "If it tests good with the tester then box is good and you need to check Blah, Blah, Blah" and send you on a wild Goose Chase.
When I had a problem a few years ago everything seemed to point to ignition box yet MSD kept saying there was nothing wrong with it and gave me the run around. Car would run a 5.09 one pass clean and then very next pass 5.49 banging, popping and missing. Finally I just changed out box and it ran like 4 passes 5.04 in a row.


I have right now in my shop a box that "TESTS" perfect to 14,000 but is weak at high RPM in the car and verified with my logger.

Some of those boxes can be repaired but do not trust that MSD ignition tester it will fool you.

Whatever you have replaced to try and remedy the problem , DO NOT replace any of these again. Continue on to the things that have not been replaced.

Your problem could be as simple as a bad ignition on toggle switch or some other non-ignition related item.

I was in the same position in 2016 with an ignition related type miss that would only happen on initial start-up. Replaced or substituted everything electrical to include the alternator and switches. I thought I had it fixed the last race of the season. Started the car for the first time in 2017 and it was back worse than ever. I removed all the wiring with the exception of the gauge lights, and re-wired the entire car starting with a new toggle switch panel and relay board I never had. This fixed the problem.

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

Discriptions/choice of words used to descibribe mechanical issues vary greatly. Fluttering and popping could be and has been the converter in many cars, seen it many times over 25 years usually after the racer replaced every ignition and fuel component, pulled all his hair out, banged his head several times and ready to list his race car on RJ.

So again, after the OP has checked, rechecked and replaced everything ignition and fuel related, spent hundreds if not thousands, pull the converter and swap it to your spare or a known good to go piece.

Good luck.

Clean the air bleeds in your carburetor.

Here’s an idea, start your car and warm it up normally then shut it down and pull some plugs and see what they look like. I had a carb issue once that would crap up plugs during warm up and miss right before the shift, after one pass it would clean up and be fine. Just a thought. I broke a few converters in my time and never had it cause engine miss or flutter or pop.

Sorry if I missed, but if you have not changed coil, do so. I fought this a couple years ago with an HVC II that always tested fine with msd tester running for 10 + minutes. But get it on the track and would act up.

rev limiter ?????

Had a 6-T MSD box, the miss was a bad tach circuit.

The tach has been tried also

Rotor phasing?

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.

quote:

Originally posted by rusty:
rev limiter ?????

Yeah, if you're in the MSD handheld and accidentally change it to a 6cyl, you can have a pretty effective rev limiter.

Posting for a friend.

I've had a couple mysterious pops and flutters over the years that absolutely sounded like an ignition issue.

1. Power valve was fluttering open/shut, only under load and at high RPM.

2. Hairline crack in the intake manifold off a bolt, causing a vacuum leak only at high RPM.

Both of these were found only after swapping out everything in the ignition system.

And yes, it absolutely could be caused by the converter changing the engine load in unexpected places. You could say that it is ultimately a fuel issue, but it is caused by the converter.

no it can't be the converter, because I read on an internet forum posted by a nobody that thinks he knows...

quote:

Originally posted by Curly1:
Fluttering, popping and missing is NOT the converter.

Lenny5160...KNOWS!

that makes 3 now that say it could be the converter.

Don't forget to check all your "grounds".
Had this issue on my wifes dragster ran great then all of a sudden half way thru the season it started missing up top.
I changed everything I could (ignition, wires, cap, rotor, plugs twice, springs, etc, etc) then finally I spent a weekend and re-wired all the grounds DIRECTLY to the battery.
Fixed it.

And YES, it also could be the converter.