holley 3310-1 780 CFM Vac Secondaries.

i had the idle speed, float levels, enrichment needles, etc. all in line yesterday.

i decided to swap the power valve to a 10.5 (according to sofakingdom's writeup at the top of the page) and have had a couple of issues.

1. under heavy throttle (in park) i am getting an occasional backfire through the carb.

would that be a sign of a rich or lean condition?

2. now when i hook up my vacuum gauge to the carb, it starts to bog a little bit. is that normal? yesterday (with the 6.5 PV) i was around 15-17" hg.

as far as the retuning with the new powervalve goes, i didnt do much because of the backfire (happened only twice in a 10 min period). i just wanted to double check a few things.

 

ok. i have most if it resolved.

the one thing that i forgot to mention is that i put some more fuel in (i thought i would give 87 a try since i have no idea about the compression, etc. i put some lucas octane booster in and no more backfiring through the carb, so i guess i will be running 89 or 93, (or i might back off the timing a little bit) when i am not going to the track.

the thing that i dont understand though is that the engine still bogs when i hook up the vacuum gauge.

any explanation for that?