Hot Rods Engine occaisonally backfires

The 318 Poly has started to occasionally backfire, just one or two coughs then its fine for another 10-15 miles then maybe another cough, otherwise its running, idling & accelerating fine, this is when cruizing on around 2500rpm, it has a Mallory YL twin point dissy, I have replaced plugs, leads, cap & rotor button with new points and condenser on hand and next in line..........however I have noted that this problem could be the start of the coil saying bye-bye..........any thoughts by the collective wisdom?.............. thanks, Andy Douglas

 

Through the intake, or exhaust?

 

What he said

Carb or exhaust. Could be your condenser, possible coil.

Hook up a vacuum gauge and run it into the car or to the windshield and see what the reading is when it happens.


Unfortunately, just cause you put a new tune up on it, it don’t mean squat. Shitty parts are all over these days and you could if just swapped junk for newer junk.

 

Backfires thru the intake..........will pull the dissy, much easier to replace the points and condenser with it out............the plugs are NGK from the same batch that I've kept aside for probably 15yrs, lol.........the leads are a premade set, the rotor and cap are genuine Mallory......the boxes at least say Made in the USA..........the points are a "FuelMiser brand, Country of Origin USA" again the box at least seems to be from the USA, lol.............as the leads were just bought individually premade the correct length I can't say where they are from tho' they as a nice dark blue colour..............lol...............might go price a new coil tomorrow while I'm at it.........lol............andyd

 

Might just be lean at that RPM range?

 

I had a similar problem and did most of the things you're doing to no improvement. Pulled the motor thinking it was internal, ran perfect on the Dyno. Someone suggested my muffler might be plugged with a mouse nest. Sure enough, it was. Without an exhaust outlet, the only other exhaust escape is thru the carb.

I feel better now having confessed my stupidity.

 

The annoying thing is that its running well, everything seems o/k then cough..........lol...........Oldschool, I'll have a look in the exhaust pipes tomorrow, its 10.30pm now, too cold to go out, lol..........Budget, I'd be surprised if its too lean, if anything its always seemed to be a little rich but I'll check that as well.................thanks guys..............andyd.

 

i had some condensors recently any think they were fuel miser got 80 miles combined out of two of them other one didn't work at all got them from repco couldn't be bothered taking them back to get more dam rubbish so used a second hand genuine ford one all is sweet now

 

That's a solid lifter engine, have you adjusted the valves lately? Maybe an intake a little tight? Lippy

 

You might have a plug wire that the metal end under the boot isn't securely on the spark plug end or in the dist. Cap all the way . One more thing to check is you don't have any plug wire that is an adjacent firing cylinder touching or laying on top of each other . Both will cause a misfire under load.