Hi All,

I've been having an intermittent bogging problem with the Firebird while racing so I've been looking to see if I can tune it out (I know the real solution to this problem is a looser converter but I'm trying to get by for now).

First step was going to make sure idle circuits were tuned then go from there with the power valve and maybe larger pumps.

So I hook up my vacuum gauge to the rear vacuum port on the carb (which I'm pretty sure is manifold vac) and found I was only at 4-5 inches at 800rpm idle (whether in gear or not). Vac didn't change hardly at all until I leaned out enough to kill the motor.

4-5" seems incredibly low (I was expecting at least 8-10ish). Should I expect vacuum to be this low with a large cam?

I'm running a 427++ BBC with:
.630/.630 lift
255/264@.050 duration
110 LSA and 104 ICL solid roller

and 850cfm Holley double pump 4150 race (0-9380 list) carb.
I'm running a 6.5 power valve, so this also has me concerned that it will always be open at idle

If that's all the vac I get, it doesn't bother me much because I don't need it for brakes or trans just wondering if this is abnormal and I should look closer for leaks. BTW: vac comes up into the teens when I rev it in neutral.

I'll start another thread on the bogging problem...

Thanks in advance,

-Chris