Thread: 350 backfires through carb

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It sounds like a timing issue. I know that you’ve probably looked at this until you’re blue in the face. The sketch below represents what you should be looking at from the top. This is real basic – but unless you’re building a race motor, the following will get you where you need to be.

Start all over with number one at TDC. Make sure that when the piston is at TDC (as indicated by the timing marks on the harmonic damper) that both valves are closed on number one. If not, your cam is out of time and there may be some big problems. You didn’t mention any bad “crunching noises” so we trust the cam is in time with the crank.

Remove the distributor cap and the spark plug wires. The distributor rotor should be in the approximate position shown. If not, you’re off and need to take the distributor out and re-insert so the rotor matches the sketch. Snug the distributor hold-down bolt but not so tight that the base of the distributor will not turn by hand. Reinstall the wires. I always follow the firing order, i.e., 1-8-4-3-6-5-7-2. This might sound basic – but do it.

Now install your timing light on number one and start the engine – it will start. The little things are really the big things

Good Luck,
Glenn