I just recently broke in my new motor, 350 AFR heads, comp 294 cam, speed demon 750, victor jr intake. The car seems to be 'loading up' real badly. I pulled my plugs out and they all look like it is running rich, and the inside of the exhaust is all black and sooty. Also when I let the car idle, the idle changes, and it will keep lowering rpm until the car dies. My question is I believe I need to change the jets, but how do I know what to change them to? Any info or ideas would be great. Also why would the idle constantly change on me?

The idle problem sounds like a vacuum leak. I'd check for that first. You might try richening up the idle mixture. That has worked for me.

If you don't have any info on the carb and what it came with, provided it still has stock jets, you'll need to open it up. I don't know about BG but Holley recommends changing 2 sizes at a time.

I've been tuning a road demon 650 on my truck. Read there instructions carefully befor messing jets. There have been acouple of very good posts on here about the steps required to tune demons. The transfer slots are very important, etc. Good luck.

install 72 in the primaries and 81 in secondaries.set idle mixture 1 turn out fire up bring car to operating temp. Then hook up vacumm gauge try to get the highest # by adjusting mixture screws.

Thanks for the info, Ill search demon tuning for any more hints. As for the vacuum leak, it is all new hoses and connections, and I know eveything is capped, so I dont think it has a leak, but ill double check, would an old pcv valve cause the idle to jump?

70sixspeed

Do you live in Rocklin California, as in northern california by Sacramento?

Actually I live in Lincoln now, by 12 bridges, but generally same area.