Jhucks03

Can anyone point me in the right direction on base timing and idle mixture settings? Having trouble getting the idle below 1300-1500.

455 with Thumpr cam, headers and qjet. Unknown HEI distributor.

Will hook vacuum gauge up tomorrow. Getting past break-in point and wanted to get it a little more dialed in.

Also, with air filter on but no lid - and then removing. I noticed idle picked up (with nothing versus air cleaner with no lid - just filter).

Fun71

10 degrees BTDC should be a good starting point for idle timing.

cutlassefi

Thumpr won’t have an abundance of idle vacuum. Chances are you should’ve opened up the idle tubes/circuits on your Qjet before installing it.
Just sayin.

Jhucks03

Ok. Suppose I’ll be taking it back off. Not a huge deal. Also seems to want to burn the eyes a bit at “idle”. I turned mixture screws a good bit either way with no noticeable change.

oldcutlass

Not with an HEI, probably 14* BTDC, no vacuum advance. The reason your not seeing any change in a/f mixture adjustments is because your probably out of the idle circuit at 13-1500 rpm.

Jhucks03

Turns out I had a vacuum leak at the carburetor base gasket. That cured my ails. Got idle down to 800-900 RPM. Only 7-8” of vacuum though (if gauge is correct). I’ll be scouring the pick-n-pull this weekend for a booster mounted electric vacuum pump off of late model GM Tahoe/Yukon/Truck.

Thanks for the input above.

cutlassefi

Problem is that cam's performance isn't worth the low vacuum, unless all you want is the noise.
Jmo.