What is the optimum vacume to have at idle and why is it important? I heard 10 inches of vacume is ideal for drivability but is too much vacume a bad thing?
I would assume things that would effect vacume could be cam's (+/-duration) as well as idle speed of course.
Would a lack of vacume suggest blow-by or bad rings?

Thanks

 

im getting more vacuum than i though i would to im sitting at almost 15 inches, but my cam is huge though.

 

I believe a stock motor runs about 15 inhg at idle . My 408 runs about 10inhg. Cams definately affect manifold vacuum. Bad valves / seats could also show low vacuum. I know vacuum is one indication of the overall health of an engine (comparing stock engines of course).

*EDIT* just checked, 408 idles at about 12inhg.

 

10 inches is the minimum in my opinion. I think we may be chasing a vac leak someplace in your set up, we will get to the bottom of it next week when we tear into it.

 

I am at 19 inches of vacuum at idle,
Mark

 

Thanks brian, I know you'll do your best to trace it out and find the problem.
But as for myself I didn't know why we want vacume at idle or what the benefits are. I know on my original set-up I was seeing +/- 14 inches of vacume and on my Typhoon I was seeing 18-19 inches.

 

i know lack of vacuum at idle will cause poor performance from your brakes on a 1/2ton(non-hydroboost) setup

 

So your brakes will hold for one thing.

 

Awesome, so I guess the main reason for vacume is as you mentioned...to determine the health of the engine. That would make sense. Depending on the problem a low vacume could mean bad valves/seats, and possibly bad rings, provided that there is not leak in the vacume lines.
How would an engine perform with no vacume at all at idle?

 

Gotcha, I must of been typing when you posted up! I remember someone had a problem with their brakes...I believe Lurius had a problem with brakes and it was due to not enough vacume!