Thread: 350 backfires through carb

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Double check your timing gears. I had this issue where my motor would not run. Wouldn't even start no matter what I did. Checked everything 10 times over, find tdc #1, check plug wires, check plugs, had fuel, oil pressure, new distributor, new heads etc....

Adjusted valves 15 times at least with the EOIC method and every other method known to mankind.

When I rebearinged this motor, I should have checked a vital thing but I didn't and it bit me in the uknowwhat. The guy who had the motor before me had installed a brand new double roller timing chain. When he installed the CRANKSHAFT gear, he used the wrong slot in the gear on the keyway.

When I went to install the chain, circle to circle(12on crank 6 on cam)=TDC on cylinder 6, was not really tdc on any cylinder. CrankCrankCrank no run, nothing but backfiring through the carb, spitting gas 2 feet in the air.

I finally figured out what the problem could be, so I took timing cover off, removed chain, removed number 1 plug, physically looked inside plug hole while turning the engine by hand with a 5/8 socket, until # 1 was at TDC(very easy to see with flashlight), Looked at crank gear, and bingo, the arrow was at 12 oclock and the circle was at 3oclock. Setting the valves was a waste due to the basic initial timing being way off. See where im going?

I pulled the crank gear, reinstalled it with circle mark at 12, and #1 piston at TDC. Reinstalled timing chain with both circles at 12 oclock position. This is #1 TDC timing. Dropped the distributor back in( wherever the rotor is now pointing is your number 1 plug post. Using this method it is impossible to be "180" out Play with the distributor until you have it where you want it and can have the room to advance or retard if you choose.

My motor fired IMMEDIATELY not even 2 cranks of the starter, and runs sick. I set the timing at 8 btdc and have not touched it. An easy way to cut off vacuum advance is to leave the hose attached to both carb and distributor and use a pair of needlenose pliers to pinch vacuum line when setting timing. Hope this helps someone out

Originally Posted by DogKrapFace

An easy way to cut off vacuum advance is to leave the hose attached to both carb and distributor and use a pair of needlenose pliers to pinch vacuum line when setting timing.

If the hose it left in place, when you pinch the hose, any vacuum in the diaphragm will be trapped and possibly cause an erroneous timing check/adjustment. Always remove & plug the vacuum supply hose to the dizzy.

Years ago I used a point & condensor style distributor but did not use a resistor to drop the voltage from 12 to 9 volts. This clause the points to ark and timiming to jump all over. It would run for 5 minutes and then overheat. What type of distributor are you using?