308 timing and ported vacuum

dougson

I thought I would bring this up just to get other input. When timing my 308 Twin-H (I have a GM style balancer with timing marks installed), i noticed that the vacuum advance does not pick up at idle, only off_idle, @ 1000 rpm. The vacuum ports on the Carter WA-1 are above the throttle plates so I assume that vacuum advance on these engines is off ported vacuum, not manifold. Agree or disagree?

Park_W

All Hudsons with vacuum advance, and most other cars at the time, used ported vacuum sources. Vacuum advance at idle didn't come along in wide use until 1967 and its emission control systems. (The other thing about Husdon Six vacuum advance is that, compared to most other cars, the amount of advance is miniscule ... 4 or 5 degrees for 1950 and later).

Glowplug

As a followup to what Park stated, the attached chart is from the September 1953 Hudson merchandiser. As you will see it provided the factory curves for the 4009 A and B distributors. These were used in the 232-262 and 308 engines in 1953-54.