So iv been driving the heck outta my 30 coupe. Over 300 miles so far in about 2 weeks. One thing i can not get rid of is the pop out the tailpipe between shifts. It doesnt do it when its cold, but after about 10 miles between shifts it has a loud backfire out the tailpipe. Seems to be worse when its retarded, but if i give it full advance, its not so bad. Also, if i drive the car for long distances, when i go to shut it off, it backfires out the tailpipe like a shotgun. This backfire occures 10 seconds after everything in the motor has stopped. Tonight it did this and blew the muffler off the car. Iv done a full tune up, points rotor the whole bit, and tinkered with the carb, and it will not quit. It stopped the backfire after shutdown after i rebuild the distributor and reset the timing. Car runs fantastic. What the heck is going on???
there is some gas puddeling in the exhaust.imo it has to be running rich,float is stuck,or the exhaust pipe is too small.i would try the using a different carb since you have already tryed the dist-timming.
My A truck does something similar when I shut it off, it likes higher octane gas. Also make sure there aint a bunch of shit in the carb bowls. Try some higher octane see if it makes a difference.......
http://www.model-a.org/problem_solving.html http://www.amazon.com/Restorers-Model-Manual-Motorbooks-Workshop/dp/0879381949 Exactly, how high octane of gas do you think they had in 1930? .. .
Exactly, how high octane of gas do you think they had in 1930? .. .[/QUOTE] Not much I'm sure, just letting him know what works for me!!
Did you check the timing, and do you know how? It is really simple, but if you don't know how you will never get it! Sounds like it's time for a downdraft and a mag
I'm not a banger man, but I had a prefect with a backfire problem once, couldn't figure it out, then found the distributor was not tight, and had retarded badly. Once the timing was reset it was ok. Could it be that your timing is retarded, so when you are adjusting it it is always a bit retarded from where it should be?? In other waors, when you have it retarded, it's REALLY retarded. Just a thought. Mart.
The backfiring is caused from fresh air entering the exhaust system,, (bad gaskets, cracked manifold or pipe, etc) aided by the above quote.
When you let off the trottle, there will still be some gas coming from the carb, but not enough air to ignite the mix inside the engine. But then the gas enter the exhaust pipe that is hot and have a small air leak letting fresh air (oxygen) in= bang. So check for exhaust leaks, does not need a big one.
I have a similar problem, so drove it to the muffler shop and got a whole new exhaust, drove it home, and the damn thing started popping again BAD inbetween shifting when the rpms are coming down.. I drive with the lever on the left side of the wheel all the way down to a 9oclock position, when I move it up to 12 it gets worse, anyway I think I'm gonna rebuild the carb if that doesn't work, out comes the crow bar
I had a truck with a 440 that if you accelerated and then let off...one..two..three..BANG goes the muffler and you could see the fire in the sideview mirror at night. I'm sure it was the dang distributor.(retarded) Broke that muffler in two.
Are you running a zenith or tillotson carb? The tillys are bad about warping the top half and the throttle bore. This leads to leaking fuel around the bowl and sucking in air after you let off the gas causing a bog when taking off and popping. Swing over to the Ford barn and ask them how to fix the popping.
My Vett would do that, I would get on her and let off and BANG and flames would come out, just rev her up and let off BANG FLAMES..... She ran fine and I never figured out why she ran like that...................
As said before you have an exhaust leak. The old exhaust manifolds tended to sag because of the heating and cooling and leave enough of a gap at the 1st cylinder to suck air. The new aftermarket manifolds are reinforced and prevent this from happening.
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