yellovette

I checked my vacuum yesterday while setting my idle mixture and got a steady needle at 12". Most manuals I've read say you should have 17 to 20 inches of vacuum. Wouldn't a performance cam with a certain amount of valve overlap account for a lower vacuum reading at curb idle.

Thx.

YV

Jack Wood

Timed vacuum above the blades will always be less and was used for emissions purposes only. Longer duration cams will result in less vacuum as I recall.

redstingray74

Another consideration is Altitude . I don't know yours but here in Central Oregon I'm at
4575 ft. and vacuum is pretty low on my 74 L82. I'm lucky with this cam to get 14
or 15 inches at idle . ( thats pure manifold vacuum with a fitting in manifold )
You also get to run a lot more advance at high areas too.

yellovette

Yup, never thought of altitude, but I live at a ski resort up a mountain so there will be some effect from that. BTW I am measuring full intake, not timed, (above the blades). I must say, the motor is running absolutely fine, no hesitation on snap acceleration.