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Phillyfanfrombirth · 08-25-2005, 03:31 PM

Hmmmm....

Causes of backfire...

Choke.

Vacuum leak / hose connected to wrong port.... the vacuum line that connects to the metering block is the one that goes to the vacuum advance, if you have one. The others are the full time vacuum sources.

Ignition timing (too retarded)

Crossed plug wires... or defective plug wires.

Poorly adjusted valves (people like to torque the hydraulic lifters down too far, then when they pump up with oil, they end up leaving the valves hanging open.)

Bent exhaust valve.

Timing chain set in a retarded position.

As far as the carb... after checking to make sure that the choke is in good working condition, which shouldn't be too difficult this time of year... the fuel bowl floats should be set at a level that allows the gas to touch the threads of the sight plug. The fuel mixture screws (2 if you have a double pumper) should be slowly turned in until the engine starts to sputter, then back off by 1/4 turn.

08-25-2005, 03:31 PM	#2
Phillyfanfrombirth Registered Member Join Date: Dec 2004 Location: South Central PA Posts: 358	Re: Backfire Hmmmm.... Causes of backfire... Choke. Vacuum leak / hose connected to wrong port.... the vacuum line that connects to the metering block is the one that goes to the vacuum advance, if you have one. The others are the full time vacuum sources. Ignition timing (too retarded) Crossed plug wires... or defective plug wires. Poorly adjusted valves (people like to torque the hydraulic lifters down too far, then when they pump up with oil, they end up leaving the valves hanging open.) Bent exhaust valve. Timing chain set in a retarded position. As far as the carb... after checking to make sure that the choke is in good working condition, which shouldn't be too difficult this time of year... the fuel bowl floats should be set at a level that allows the gas to touch the threads of the sight plug. The fuel mixture screws (2 if you have a double pumper) should be slowly turned in until the engine starts to sputter, then back off by 1/4 turn.