Motor 'spits' once in a while

Well, a couple of weeks back I went and visited my good friend Craig formerly of the late great Macs Jeeparts (We lost a 'beard of knowledge' God Bless you Mac) a couple of years ago.
Anyway, Craig had to move up the Freeway to Jefferson and on the way back Black Betty ('78 CJ5) was getting pushed by maniacal traffic on I-5. In the process I broke loose some carbon and closed the gap on one of my plugs, shorting it out and causing a miss, with that the exhaust tune changed and I changed out all of the plugs. This took care of the miss, but now I have a new issue. Randomly and only once or twice in my 12 mile commute the motor (AMC 360) 'spits', (like a small backfire through the carburator) note that this is random and normally only once a day. The exhaust note has not yet returned. This occurs when the motor is at operating temp and cruising on the Highway, this 'spit' has yet to occur during slower, stop and go city driving.
Since, I've run a tank of Premium fuel through her and reved up the rpm's shifting at 3800 rather than my usual 3000.
I'm leaning toward a fuel issue and if I have time I'm going to check my fuel connections tonight, and perhaps change out the fuel filter - one of the few items I have'nt touched since first buying 'BB'.

I welcome any other opinions as after my 11 hour work day my mind is on wind down and I'm zombie'n pretty hard.

Thanks and a lift of the lynch lid.
Gus

 

I think I'd want to check the compression and vacuum with an eye to a valve problem.

Maybe unrelated - but I had an AMC 360 from that era, and was always fighting a detonation/pinging problem when using unleaded fuel. How did your plugs look, for color?

 

Howdy PeteL, save for the one that was bridged, the others were light tan in color and gap was steady 36 - 38. The odd thing is this single spit only happens at the most once per day, yesterday not at all.

 

Well today at work I slowly ran a little over a pint of water down the primaries (not much smoke at all) and ran her out on the Highway and the "pock snapple khrap" that I was accustomed to returned and not one 'spit', 'blip' or 'belch' came through. I'll rap it out on my commute home tonight but I think I'm on top of it now.

 

Well nutz, the spitting and off exhaust note had returned but, I recall when I was chasing an overheating gremlin a couple of years ago I seem to remember retarding the timing some, going to try to find my light tonight and put 'er back to 10*

 

Had to buy a new timing light as my old one went MIA, turned out the timing was at 13* advanced, rolled it back to 7 (within spec.) but I think there's some other issue at play here. Going to pull a few plugs tonight and see what they tell me. Ultimately it may very well be a valve problem.

 

Well, went to work today and not a peep of misfire out of the motor, thank Heavens!

This could be due to finding a little corrosion on the coil terminals and finding the timing issue may have done it... time will tell.