General Category > Quadrajet Carb Talk and Tips
041 and 455 pontiac vacuum
BLUE TA:
hi guys, Im building a 455 and just bought a 041 cam. I know cliff has had great results with this combo. my question is will I have enough vacuum for my power brakes. 6x8 heads, cliff designed q jet, 68 oem intake and th 400 2500 stall. ra exhaust manifolds. 74 TA. will I need rhoads, more compression? thanks, mike
Cliff Ruggles:
Are you going to zero deck the block and use a thin head gasket?
The 6X-8 heads are 101cc so the compression ratio will be pretty low. I'd do what you can to get it as high as possible/practical if you want to run the RAIV cam in it.
I like to see at least 9.5 to 1 compression, 10 to 1 or a tad more is optimum for that cam in a 455 build with iron heads.
I did ONE 455 here with 6X-8 heads on it and it required Rhoads lifters to be happy and actually worked out well. Just a tad "soft" at low RPM's but from 3000 rpms and up it was an ANIMAL!.......
BLUE TA:
thanks cliff, yes I will increase compression to at least 9.5 to 1. will it stil have enough vacuum for the brakes. will I need rhoads for sure?
Cliff Ruggles:
Yes, it will work best with Rhoads lifters and 9.5 to 1 is a good move as well......
old cars:
Something like a Crower 60918 would have been a better choice. And no rhoads lifters required to crutch it. That 041 cam will have no balls on the street unless you have around 411 gears.You can to better
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