W-31 owners. I'm looking for bone stock W-31 motors. I have built my motor as close to W-31 specs as is possible with todays components. I'm getting 10 inches of vacuum at idle. That seems lower than what I'd expect from a factory motor. I know 82* of overlap is considerable for 350 cubes, but it still seems like it should be closer to 14 inches. So to you stock W-31 owners, if you'd care to, could you throw a vacuum gauge on your motors and tell me what you are getting? Include how much flutter you're getting. A little, a lot, none.
Thanks a bunch.

 

Both of my W31s have 8-9 inches at idle. My camshafts are originals.

 

Interesting. Well I guess I'm right in there then. Thanks Joe.

 

If you have vacuum advance, connect it to full manifold vacuum and that should increase the idle vacuum. It worked well on my engine.

 

I'm using a Mallory mechanical advance distributor. As of now, I don't have any parasitic vacuum draws on the engine other than the PCV valve and the line to the modulator. Next summer the auto is coming out and the 4 speed is going in so that will leave only the PCV valve. I thought I was low, but according to Joe, I'm right in there. So I'm good. Engine runs fine. I just thought that strolling into an Olds dealer in 1969 and finding a car with only 9 inches of idle vacuum would be pretty radical. But I guess not.

 

That cam is why the cars had manual brakes - not enough vacuum for the booster.

 

Yep. I hear ya. I think 16 inches is the iffy spot for PB. Pretty gnarly for a showroom car. But hey, the W-30 had 328 duration with I think 108* overlap. That's nuts.

 

I wish every true Oldsmobile fan could drive a factory W car. Completely different animals. I had a friend with a 70 W-30. Kind of a beater but man did that car run. Then one of my brother's had his W-31. That car pulled so strong.

 

I think that’s fairly accurate based on my experiences. My engine had 14-16” bouncy vacuum with the 217* cam and the power brakes were iffy. After much tuning I got it to a steady 16” vacuum and the brakes work very well, they seem the same as the factory setup that had around 20” vacuum.