gregford

i have a freshly rebuilt 351 clevo with twin point mallory ignition system 650 holley dp, stock intake manifold
and it has an intermittant missfire from both banks but mainly the right bank when i'm warming it up and it only at idle
what could be causing this????
where do i start looking to fix it??

brenx

Backfires through the exhaust I gather? If it is? Try a plug change. I had that same problem. I found what was causing it was the dizzy needed to be regraphed to suit my cam (it's graphed to suit a stocker/mild setup). Not enough initial advance was causing it to fuel up and foul plugs.

Replace plugs and make sure the timing set appropriately and go from there.

Brenden

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XB Fairmont (street car) 11.07@123.02mph.

STROKEXD

Is it like a shudder? Would guess it is just the fuel/air ratio it's getting shows up when it is cold ie a little on the lean side.

Not too much cause for concern.

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Tote

I ve had similar symptoms with a loose manifold. When the engine is cold the maifold leaks vacuum which makes the engine run lean, when everything is warm the manifold seals and the thing runs properly.
Regards,
Tote