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Transition backfiring.

Old Feb 12, 2008 | 06:07 AM
  #1  
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Default Transition backfiring.

Just rebuilt it for the 3rd time this week, the needle valve was sticky and the last few kits I'd bought didn't come with the needle/seat in the goody bag but this one did .
Great. So I rebuilt it, no flooding. But now I get fuel starvation at WOT. Float level is set at 1/4" (8/32" as recommended by the sheet that came with the rebuild kit), fuel pressure read 3# in the line from the pump to the carb last week, and I assume that it didn't change. Anything else I should look at?

This may be totally unrelated, but when my engine's cold I get a backfire out of the intake when transitioning off idle under load. Timing is set to 12* initial, 36* all-in with vac disconnected and plugged.

Ordinarily I'm pretty good with carb'd cars, but this ol' 350 doesn't seem to want to cooperate.

EDIT: Checked the carb's filter because the carb itself was full of crap of unknown origin when I cleaned it again and it seems that that was the problem. No idea why I didn't think of that before. Anyway, I'm still experiencing cold backfires though, so if anyone's got tips on that, let me know.
TIA.

Last edited by murraybs; Feb 12, 2008 at 06:11 AM.
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Old Feb 12, 2008 | 06:20 AM
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Is this the original carburetor for this car? The fuel pressure is low. Are you sure the fuel pump is able to supply enough fuel volume? Backfiring through the carburetor is a lean condition. This may be choke related. When it leans out at WOT is this under 3000 RPM or over?

BigBlockk

Later.....
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Old Feb 12, 2008 | 09:54 AM
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....and I would check even the timing...... often backfire can depend from a retarded igniction!
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Old Feb 12, 2008 | 11:55 AM
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Backfiring when cold is indicative of a lean setting of the choke. Richen it up.
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Old Feb 12, 2008 | 05:39 PM
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Thanks guys, I appreciate it.
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