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nkaminar · 06-17-2025, 05:45 AM

Russell, In my car, while going down a grade, I can cause the engine to backfire out the exhaust by retarding the timing. Unburnt air/fuel is going out the exhaust because it is not getting burnt in the engine and the retarded timing ignites it.

Now that you have re-timed your car, how is it running? Is it still low on power?

The 30 degrees of backlash that you reported in your distributor worries me and may be related to your backfiring. Investigate where this is coming from and fix it.

A leaking exhaust valve can cause the unburnt air/fuel in the exhaust system to ignite when going down a grade.

You also reported that the point gap was different for different positions of the distributor cam. This indicates that there is wear in the distributor or that the cam is bad. This may be related to the backfiring as there will be different timing for different cylinders. Either fix this or get a different distributor without this problem.

06-17-2025, 05:45 AM	#4
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 5,855	Re: Backfire on a down grade Russell, In my car, while going down a grade, I can cause the engine to backfire out the exhaust by retarding the timing. Unburnt air/fuel is going out the exhaust because it is not getting burnt in the engine and the retarded timing ignites it. Now that you have re-timed your car, how is it running? Is it still low on power? The 30 degrees of backlash that you reported in your distributor worries me and may be related to your backfiring. Investigate where this is coming from and fix it. A leaking exhaust valve can cause the unburnt air/fuel in the exhaust system to ignite when going down a grade. You also reported that the point gap was different for different positions of the distributor cam. This indicates that there is wear in the distributor or that the cam is bad. This may be related to the backfiring as there will be different timing for different cylinders. Either fix this or get a different distributor without this problem. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 06-17-2025 at 05:52 AM.