Firebird Nation banner

How much vacuum should I be looking for?

1197 Views 4 Replies 4 Participants Last post by  JoePeek
I've got a 455 60 over, 6x-4 heads, summit 2802 cam, Torker 2, Holley 770 street avenger, long tube headers, and I am working on dialing in the carb. First engine build for me and I am trying to figure out how much vacuum I should expect. My understanding is that with this cam I won t get a ton, but I'm trying to get my head around what to expect. With a little tweaking I am at just over 15.

Any advice from more experienced builders I appreciated.
1 - 5 of 5 Posts
Brad , I ran the 041 cam which is close. I used roads lifters and had 16-17 at 750 rpm. I'd say 15-16 without roads lifters would be good. You'll have enough for power brakes with that. I'm at 11-13 with my HR setup and no problems with the brakes.
Cool, thanks for the input. Like I said, my first build attempt and I seem to be getting lucky getting things working, haha.

Planning on bumping up to a bigger carb soon, but want to get driving in the meantime.

Thanks again.
I got a Comp XR276HR in a,.030 over 455HO. It has 224/230 @.050. It gets about 16 in. Hg at 800 RPM idle. But that is with 15 degrees initial timing and 15 vacuum timing all in at 14 in. Vacuum. So it is at 30 degrees when at idle.
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.