Holley Carb Question

[cwestra]

This is interesting. I'll assume the secondary carbs are vacuum operated here. What happens when you try to put the car in gear? Usually with a vacuum leak, it will want to stall unless you give it gas. Are you certain you are idling at 1100RPM? The original Rally gauge tachs tend to read higher than reality unless they have been rebuilt or re-calibrated. If you have an aftermarket tach, then I'm sure it's accurate.

Yes, secondaries are vacuum.  The car is a 4 speed so am not able to evaluate when in gear.  I am pretty sure it is near 1100.  The speed sounds right when idling, in fact I'd probably have it close to this speed anyway, it's just that I shouldn't have to have the idle speed screws backed out to do so.  That, to me, indicates something is not right.

[cwestra]

Hummm good point Mike!
Are the carbs new? Just wondering if the throttle shafts are worn , letting air by?

No, the carbs are as old as the car is, I'm pretty sure.  I did check the shafts and although there is probably a little more wear there than should be, I don't get a change in engine speed when blasting that area with Gumout.

What about the possibility of an air leak somewhere else, like manifold/head interface from a defective gasket?  Would this cause the problem I am experiencing? 

[Chryco Psycho]

2 problems come to mind 1 is the power valve staying closed as in is there enough vacuum below 1100 to keep it closed , the second is advance springs in the dist , I got caught with this once , it would barely idle at 400 rpm then if you increased the idle speed slightly the advance weights would advance the timing causing the idle to jump to 1200 rpm

[cwestra]

2 problems come to mind 1 is the power valve staying closed as in is there enough vacuum below 1100 to keep it closed , the second is advance springs in the dist , I got caught with this once , it would barely idle at 400 rpm then if you increased the idle speed slightly the advance weights would advance the timing causing the idle to jump to 1200 rpm

I did check manifold vacuum and am getting around 17", which should be more than enough to keep the 6.5 power valve closed. 

I know you had mentioned the problem you had with the mech. adv. weights before, and I have since replaced my old distributor with a MP electronic but no affect on idle speed, so I am kind of ruling that out too.  Plus, I was never able to get the extreme low idle (400 rpm) condition that you also had.

What about a vacuum leak between the head and manifold underneath?

[Chryco Psycho]

definat possibility or it could be a vacuum leak into the brake booster also