[webcat]

When i was young i had a friend put a used pontac 350 in my 1975 pontiac Lemans , it was just a stock engine , well anyways when he gave it back to me he put a single side out exhaust on it with a single glass pack , I dont know what he did to it but everytime i would rev it up as the rpms came back down it would make this awsome popping sound !
RRRRRummmMMMMM pop pop,,,,,,pop pop,,,,,,, pop pop pop pop the last four or five pops would be kinda faster then the first few
each time i reved it up when ever the rpms came down it would do this each time slightly different
Anybody know how he may have did this ? After he put it in i did'nt see him for awhile to ask and when i did see him i forgot to ask.

 

[Mr_Bowtie]

Is it possible that the motor was just running rich/had a miss at higher RPMs........raw fuel in the exhaust will cause back firing. :shrug:

 

[webcat]

Whatevever it was i suspect it was intentionally done while he was tuning it !

 

[astro355]

Is it possible that the motor was just running rich/had a miss at higher RPMs........raw fuel in the exhaust will cause back firing. :shrug:

With carbureted engines, if you step on it causing the engine to be rich and then let off the gas, there will still be a momentary rich condition causing excessive fuel to be in the exhaust. That is what causes the popping. It has nothing to do with the exhaust to speak. Back in the day, we would explode mufflers by turning the engine off while we were still moving down the road. The mechanical fuel pump would still pump fuel because we would leave the manual transmission in gear and then pump the gas pedal. Once we restarted the engine, you would get a tremendous backfire. It was really cool at night!

 

[Jasen]

Is it possible that the motor was just running rich/had a miss at higher RPMs........raw fuel in the exhaust will cause back firing. :shrug:

. Back in the day, we would explode mufflers by turning the engine off while we were still moving down the road. The mechanical fuel pump would still pump fuel because we would leave the manual transmission in gear and then pump the gas pedal. Once we restarted the engine, you would get a tremendous backfire. It was really cool at night!

Kids :naughty: :lol:

 

[Mr_Bowtie]

Is it possible that the motor was just running rich/had a miss at higher RPMs........raw fuel in the exhaust will cause back firing. :shrug:

With carbureted engines, if you step on it causing the engine to be rich and then let off the gas, there will still be a momentary rich condition causing excessive fuel to be in the exhaust. That is what causes the popping. It has nothing to do with the exhaust to speak. Back in the day, we would explode mufflers by turning the engine off while we were still moving down the road. The mechanical fuel pump would still pump fuel because we would leave the manual transmission in gear and then pump the gas pedal. Once we restarted the engine, you would get a tremendous backfire. It was really cool at night!

Sounds like fun to me! I don't have much experience at all with carbs, so thanks for the explaination! I just know unburnt fuel causes backfiring.