Engine Backfire (Need help)

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Mar 8, 2003 | 10:07 PM

Abroadwa

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Joined: Feb 2003

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From: Arizona

Engine Backfire (Need help)

I just recently installed a rebuilt 302 1970 mustang engine with several goodies. I installed an MSD offroad ignition with a mallory coil and unilite distributor. I have a holley truck avenger carburetor and holley electric fuel pump (blue). Well today was to be my big day. I have gone over every little detail that I could think of. All I get is backfiring back up through the carburetor. No matter how much I adjust the distributor (POW). I have again checked all wiring, vacuum leaks, checked distributor installation. I am at wits end. Can anyone guide me where to check next.

Mar 9, 2003 | 08:33 PM

Ratsmoker

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Joined: Feb 2001

Posts: 6,624

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From: Missouri

Engine Backfire (Need help)

Are you using a timing light? When I get ready to fire off a new engine I will take the passenger side valve cover off and rotate the engine while feeling the number 1 piston through the spark plug hole and watching the valves move. You can find true TDC this way as you can watch the intake valve close. Once the intake valve closes and the piston comes back up then you can point the rotor in the general direction of the number 1 cylinder wire on the cap. This way you know you are not 180 degrees out. Also depending on which cam was used in the rebuild you may either have a firing order like the 351W or the old 302 firing order. This is something you want to check into before cranking anymore. Cranking a new engine for long periods of time can damage the lifters.

Mar 10, 2003 | 02:41 PM

ehret

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Joined: Jan 2003

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From: Chesapeake

Engine Backfire (Need help)

I agree, take the #1 plug out and ensure you are TDC. Either stick your finger in and feel for the air coming out or the best way is stick a straw in and turn it by hand. If you are one gear off it will not run right. One time I thought I was TDC but I was actually 180 degrees out and my air box exploded when it backfired, not good.

Mar 10, 2003 | 07:20 PM

Abroadwa

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Joined: Feb 2003

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From: Arizona

Engine Backfire (Need help)

Thanks guys. I figured it out yesterday morning. Even though everything is an early model 302 the machine shop gave me a 351W cam since in put 351W heads on it. Runs good now.