Vacuum readings

[whiteowl]

Does anyone know what the factory manual has listed for proper vacuum readings at idle for a stock 440hp 1969 R.Runner w/man. trans. My readings seem to be consistent but rather low. Any help would be appreciated.

[timty2]

I don't know if this helps, since I have an Auto Trans....

I just checked my readings on my 69 440 Charger to select the proper power valve. The vacuum reading at Idle, in gear, was 13 in hg. At idle/in park it was 15-16 in hg. This is after an Edelbrock intake manifold and Aluminum heads were installed w/demon carb. Still stock R/T camshaft though.

I took a baseline reading before we started the parts swap (Stock heads, Dominator Manifold) and the best idle vacuum reading was 10-11 in gear, 13 in Park.) I think we had some leaks at the intake gasket.

[Doug Wilson]

I think you should be looking at 14 or 15 in gear, and 16 to 18 out of gear, with a stick, but I don't know the factory spec. I'll check my book and let you know.

Is the car bone stock? How many miles on the engine?

[whiteowl]

The engine is@ 30 over, 11:1 compression and 'purple shaft' cam (280/474). There are approx. 2200 miles on it. The readings I'm getting are around 12-13in hg. at idle 750-825rpm. I haven't done any leak detection yet but I'm suspecting a stuck lifter. I hear a louder than normal click/suck sound comming from the passenger side, either #4 or #6 cylinder. I believe I should be getting fairly higher than stock but I'm not sure what the stock readings should be around. My readings are comming from the brake port off the backside of the intake. Thanks for any help!

[Doug Wilson]

With that cam, you're right in the ball park. The hotter the cam, the lower the vacuum.

If the vacuum guage is fopping around, either at idle or under load, that can indicate a number of things. I don't believe you have a vacuum leak.