vacuum at idle?

[MoparN75]

What is the average vacuum at idle on a stock '88 turbo motor? I had about 13, advanced the cam 2 teeth and lost about 2". Think I'll try retarding it 3 teeth and see what that does. Any thoughts or suggestions?

[GLHNSLHT2]

a healthy 2.2 should have 16-18" a 2.5 should be 18-20 at minimums.

[shadow88]

Ok, for starters, moving "teeth" at a time won't get you any more power anywhere. This has got to be done a few degrees at a time, usually in 2 degree increments. I would consider 16 inches or more to be about normal.

[MoparN75]

Ok, for starters, moving "teeth" at a time won't get you any more power anywhere. This has got to be done a few degrees at a time, usually in 2 degree increments. I would consider 16 inches or more to be about normal. Thanks for the input. But suppose someone had installed the cam incorrectly. Like placing sprocket reference marks level instead of parallel to the head plane. I'm not actually looking for additional power right now anyway, but rather max vacuum at idle.

[zin]

You'll want to get an adjustable cam gear, set it to zero, then dial in the cam "straight-up" to see what "normal" would be,then bump it 2* at a time, both up and down. I'd bet you'll see the biggest changes within 6*+/-. I don't recall how many degrees one tooth represents, but it is a large swing, the kind that tends to swing you right past the "sweet spot".

Naturally, you'd want to confirm proper "stock" pulley install, which can be a little tricky due to the engine's inclination towards the firewall and one's natural tendency to use something other than the head as a reference for what's "square". A mirror can help to see if the marks on the pulley align/square with the head. Hold it so it faces the pulley and look at it from the driver's side. There's also a timing light method, but would require the ignition timing to be set to zero, which might be a bigger pain.

Might want to do a leak-down or compression test to see if it's practical to expect higher vacuum ...

Mike

[MoparN75]

Might want to do a leak-down or compression test to see if it's practical to expect higher vacuum ...

Mike
Yeah, it's beginning to look like with stock components 14" is as good as it gets.