Backfire...revisiting

[Broncojunkie]

Still say your timing is too high. What RPM is the 44 degrees all in ? The only engine I have ever seen use that much timing was a big block Chevy whit over 12:1 compression and very large domed pistons and ethanol racing fuel. Because of the domed pistons, the extra timing is need for the flame front to travel up and over the dome.

Not knowing when your timing is all in doesn't help solve this problem. If it doesn't come in till high up in the rpm range, than that explains the poor running at lower total advance in the 30's. All in should be in @ the 3000's rpm range. I don't recall if you mentioned the initial timing. It should be @ 14 at idle in the 750 rpm range. There may be a problem with the distributor rotor not being in proper phase with the cap wire post. This could cause cross fire and back firing like you were having. Being that it is an after market distributor.

Timing is the same with stock distributor. I've had multiple distributors in it....4 iirc. Two msd billet and two stock distributors. No difference. I did some reading on rotor phase, but that was a little over my head and didn't seem like it applied to my situation.

Just to reiterate, I had an occasional slight stumble during acceleration which was only noticeable under load. The backfire came only on deceleration and only after getting in the throttle pretty good. Putting around town wasn't bad, other than it just didn't sound or feel "right". It was lacking in power and letting off the gas, it seemed to not breathe well. I say that because that's exactly how I described it to my friend recently. Literally had what I can only describe as a "cough" when i let off the gas to change gears. In retrospect, it makes sense to me lol

Just listening to it, I'm sure the timing is all in by 3k. When I get home in 3 weeks, I'll be installing the semi-permanent aftermarket tach. (I may eventually try to get the 4 cyl tach to work with the v8 ). I'll verify it, but she sounds pretty rowdy by 3k and timing light shows I'm all in just before that point. With the stock msd advance springs, it was well above 3k. I believe it was in the 36-3800 range but it was last year, so I can't remember exactly.

[Jerry peachuer]

Not sure if petronix and MSD will play nice together not sure on that

But all of your part swapping should give you different results and most of all your part swapping shows no difference
This is what leads me to think wiring

That is a magnetic pick up and if your programmed otherwise not sure if this would result it wonky results for timing or what you're seeing

Sounds like your close if you added more timing and air cleaner and your at 50-60 degrees and it's running stronger than ever and if you don't hurt it then something is not happy electronic wise but your happy then that's a head scratcher for sure

Or your crank key way is out of sync where it should be (machined) to where dot to dot is maybe it's far stretch but interesting stuff

Aftermarket is fun stuff

Good luck