Hey all, Im working on a project that I picked up around the first of the year. This is a pretty radical sb chevy with an Edelbrock Pro-Ram intake and two 450 Holleys (list 9776). Kind of a dumb question here, but I thought Id ask since Ive never ran a motor with dual carbs before. The carbs should be set-up exactly the same, right? The reason why I ask is that I went to re-jet the carbs and I found that the rear carb had 54 main jets and a 2.5 power valve; the front carb had 64 main jets and a 3.5 power valve. Thanks
Typically on most intake runners setups when the carbs are running straight the jet size and powervalves should be the same. A portion of your cylinders could be rich while the others are running lean. Check your plugs and see what effect the differences made on how they're burning.
The best i can remember... a 9776 is a 660 center squirt Holly carb. They were "THE SHIT" in the '80s meaning EVERYONE who could afford them ran them on there street racers. they should be TWINS, all the same internals
Your plugs should tell you which size to use. example... If you see they are running rich in the back cylinders and fine in the front. Replicate the good carb jet and powervalve sizes in the front. Or vice versa..
Thanks guys. The car was running fairly good with the "un-balanced" setup as far as I can tell. I went ahead and put 52 main jets and 2.5 power valves in both carbs now, and actually it seems to idle a bit better. Still seemed a little rich though, I think I will go to 50 main jets tonight. BTW, this car was running open headers and was from Oklahoma. It now has an exhaust and is at 5000ft elevation, so I am still trying to compensate for those things.
YEAH, THATS THE NUMBER ... BEEN AWHILE SINCE I EVEN THOUGHT ABOUT 4bbl HOLLY'S... I STAND CORRECTED !
This may sound goofy, but if the car was set up as a drag car,could the carbs be set that way for inertia reasons?I know cars that launch hard have the fuel cells up front for this reason.