BOUGHT A 850 HOLLEY THAT WAS REBUILT AND THEY HAD 50CC PUMPS ON FRONT AND BACK ANY REASON FOR THIS?????

Been running 50/50 on my 750's and 850's for years. I dont even remember why for sure, but I think I was chasing a bog and went to a 50 up front and never went back to a 30. I do have a 30 on a sbc with a mini blower, only because a 50 wont fit unless I put a spacer under the carb.

Many people put them on chasing a tuning issue. Sometimes the combination needs a really long shot. They usually don't hurt anything either unless on gas the pump shot is so long that it goes too rich when the mains come in.

My alcohol carb only has 30cc pumps on it racing Footbrake.

Yes, on my old combination. At that time, I was running a solid flat-tappet Comp cam that probably had more duration than what the engine wanted, and a converter that was too tight. It had a persistent bog, I kept tuning and modifying, tried every possible Holley pump cam, eventually got rid of the problem except for the occasional times it would pop up unexpectedly and take me out of competition. So I put the 50cc pump on the front and never had any issues after that. I would go ahead and try it as-is, it may be work fine for you. I have bolted that carb on my son's moderate BBC Chevelle for track duty, and it works great on it.

Nothing wrong with 50cc pumps, just use 30cc cams with it. Green or blue are my usual cams.

quote:

Originally posted by jmarkaudio:
Nothing wrong with 50cc pumps, just use 30cc cams with it. Green or blue are my usual cams.

Been running dual 50cc pumps for around 15 years on all my double pumpers. You don't have to use the full shot as explained above.

I use EFI now & should have switched over long ago!

2BKING

quote:

I use EFI now & should have switched over long ago!

Agreed, using only MFI prior.