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Old 04-30-2004, 10:40 AM
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back firing

I recently overhauled a 76 chevy 350. New oe cam, timing chain, pistons, rings, oil pump, fuel pump, Edelbrock intake, and Holley 600 carb. I'm using a single point distributor and running headers. The engine runs and idles ok but after it has been driven for about 15 miles or so it starts backfiring. The timing is still on the mark when checked. Thanks.

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Old 04-30-2004, 11:03 AM
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A little more info please. Is there a miss along with this backfire or just a popping in the pipes? Make sure that plug wires for cylinders 5 and 7 are well separated and if the wire must cross each other make sure that they cross at a 90 degree angle. Small block chevys can cross fire between cylinders 5&7 real easy. Is this backfire at cruise, acceleration or full power?
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Old 04-30-2004, 11:09 AM
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First off get rid of the points and go to a HEI, points are pretty much a waste of time. Also check the float levels, fuel pressure, and fuel shot at the carb, also check for vacuum leaks and valve train adjustment if everything else checks out okay. is it back firing from the carb or the exhaust? through the carb mostly indicates a lean mixture but can also be caused from valve train and timing woes. back firing from the exhaust can indicate ignition problems as well as other areas I pointed out, the first thing I would do when the vehicle started back firing would be to check the float levels and etc, then I`d do a spark test, if the spark is yellow it means it`s weak, blue shows a strong spark. It was recently I ran into a problem like this on a friends vehicle, after going with a HEI the problem was solved, if you do so make sure the HEI recieves a 12 volt signal.
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Old 05-01-2004, 03:17 AM
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Although HEI is a good idea, I have run points just fine... (no offense double: they worked for daily drivin just fine...if i had room to convert i would - however, I am looking at the Pertronix upgrade that would keep the points housing but use an electric module in place of the points... spendy tho')

I would check your fuel pump too - it could just not be gettin' the go juice.
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Old 05-01-2004, 08:51 AM

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is the resistor wire to the coil bypassed allowing the full 12v to the coil causing it to overheat?
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Old 05-01-2004, 09:24 AM
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One little thing you might check is the condenser in the dist. It dosen't happen very often, but I have seen them act that way.


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