Popping/backfire during upshift
- Thread starter Sparky
- Start date
Bruce Adams
Well-known member
Open the GAV resulting in a RICHER mixture, and also do something about any exhaust leak, say at the manifold to exhaust pipe junction.
Purdy Swoft
Well-known member
I would first try opening the GAV a little bit, can't hurt to try. Sometimes an exhaust leak will cause popping when you decelerate. Check the manifold clamp. I would also look around the exhaust manifold for black spots that would indicate an exhaust leak between the manifold and block. you may need to replace the manifold gasket,
Pot metal carburetors such as Tillotson and Marvel are known to warp and cause vacume leaks which in turn causes the engine to run lean. Running Too lean will cause popping amoung other problems.
Pot metal carburetors such as Tillotson and Marvel are known to warp and cause vacume leaks which in turn causes the engine to run lean. Running Too lean will cause popping amoung other problems.
Sparky
Well-known member
I've got a Zenith so warping shouldn't be an issue. The carb manifold gasket is new. I have been running with the GAV about 1/4 turn open, so I'll try 1/2 turn and see if it helps.
My exhaust clamp is tight, but that doesn't necessarily mean the connection isn't leaking a bit. I did order a gasket a while back but it didn't fit at all. Are there different styles of exhaust connection? Mine simply has a flare in the exhaust pipe which clamps up to the rounded end of the manifold.
My exhaust clamp is tight, but that doesn't necessarily mean the connection isn't leaking a bit. I did order a gasket a while back but it didn't fit at all. Are there different styles of exhaust connection? Mine simply has a flare in the exhaust pipe which clamps up to the rounded end of the manifold.
Purdy Swoft
Well-known member
I use the copper clad late 31 manifold gaskets. They are wider and give a better chance for a good seal between the manifold assy. and the block. Check the manifold with a straight edge for warpage. I would check the points setting and timing. If the fiber block on the points has worn this will decrease the gap. Points gap effects timing, too small of gap retards timing, I run my model A with the points set at .022 . Slightly retarded timing or running with the spark lever TOO far up the quadrant will cause popping when decellerating.
dmaxweb
Well-known member
What about several wraps of 1" wide foil tape? I would think the heat melting the adhesive would "fuse" the wraps together and make a tougher seal compared tinfoil alone. Probably smoke just a little bit the first time you start the car - no more than a sticker on a new muffler burning off.
Patrick L.
Well-known member
A couple things.. 1. To help fix an exhaust leak[they can be stinkers to fix], make sure the manifold aligns well with pipe and a large cheater pipe in the exhaust pipe/muffler with some muscle works for this.. I install a short piece of exhaust tube inside the pipe and manifold and seal with exhaust goop[technical term] along with a strip of sealing material[ welding glove,etc] between the clamp and pipes.. 2. I get a pop at times upon up-shifts if I don't close the GAV [ fuel mixture] a bit after the engine warms. But, it'll also have muffler explosions for about a minute if the GAV is open too far during sudden and long decelerations.. Mine likes to be run with the GAV open 1/2 turn upon start up/warm up and then back to 1/4 turn after the first mile or so..However, I keep forgetting that I use a Tillotson ..
Your SUCKING AIR
roccaas
Well-known member
Try replacing the condenser. A cheap and correct fix for Ignition Off Backfires.
roccaas
Well-known member
That is always my reminder that I have left the spark advance on retard (lever up) from warming up the engine.