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Discussion Starter #1
Still trying to sort out problem(s) with 331, Speed Pro 9.4-1,s, Comp XE 274, Holley Street Dominator/ 80508 vac sec (68 in primaries, .31 sqirter), Sportsman II, Hokker Super Comps (1 5/8), small body HEI 10 initial 34 total @2400.
Car backfires through carb when floored.
Lean right?
Should I be concentrating on carb and fuel delivery, or looking at some tweeks on timing?
Also, with a non-fluid damped fuel pressure gauge, does the gauge flutter (with car running)?
Don't have a lot of vacuum (9" @ 900 rpm,s).
Car runs good when you ease into throttle but backfires when quickly floored.
What should I be looking for?
AJ
 

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Make sure you distinguish between a backfire and a pop ... A backfire will usually come from incorrect timing or plug wire cross ( off chance you could have a bad valve spring not closing valve completely ... ) ... A pop will occur on lean condition or accelerator pump incorrectly adjust ( not squirting when first depressed ) or a plugged squirter ( maybe a piece of trash ) preventing fuel delivery ... in these cases the throttle plates are opening to allow more flow, but you need that initial big squirt of gas to compensate for teh sudden gulp of air the engine receives when first floored ...
 

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Discussion Starter #3
Is there anything in fuel delivery (pump, lines, etc) that could induce the backfire.
Checked with air cleaner on and could see fire from carb so I assume that is a backfire.
Would a compression check indicate bad valve or cam problem?
AJ
 

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Sounds like a lean backfire to me. Check to see if pump arm moves at the same time as throttle. If it does, go up about 2 sizes on squirtor and move time up to at least to 14* with this cam.
 

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Sorry--I see that you already have a 31 which should be big enough. Try different pump cams . Pink seems to be best all round one--also try # 2 position on pump cams.
 
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