what is the normal vacumn reading
 

vacumn.. i constantly get about -20 for my vacumn reading. someone said it could be cause i have a cracked seal.??? im all confused. i thought -20 vacumn was normal??? what is normal and what does it all mean.. thanks

20 is normal actually it is a good reading, prolly 17-18 with a/c on....

-20 what? I get about 500 mmHg (~20 inHg) or slightly more on mine, which I think is pretty normal.

20 inHG is normal? I've gotton 15 inHG ever since I got my boost gauge. I got my gauge when I had about 5k miles on this engine. I think that was about 5 or 6 months ago. My FD doesn't seem to have as much power as when I first got it, but that may just be me being paranoid. Should I be worried about anything?

I get ~14psi @750 RPM with Pettit Intake, PFS- IC,DP,MP,CB. Runs fine. 20psi is GREAT for modded, and normal for stock. I've never seen that much.
~Tom

There have been numerous conversations on this topic. You might be able to find some by searching the forum. 18/20 is usually for a non-ported motor while 14/15 is for a ported motor .... usually. I get 14/15 on a ported motor with 3 mm apex seals.

uh oh.. i thought i was getting good readings. @ idle i get 15-16 vacuum. and then cruising w/o the pedal on the gas peddle. i get about 20. Is this correct or is there problem with my readings?!

Correct readings, weaker than brand-new motor.
~Tom

I have a street ported motor w/ 3mm apex seals, and @ idle my vacuum readings are at 15. This is normal right? as my motor get older will the vacuum readings get higher? or lower?

Lower

So should I be concerned about my 15 inHG vacuum? My motor isn't ported or anything and it has 11k on it.

How is your idle? You might have a small intake leak. Nothing to get to worked up about. How much boost to you get?

My idle is a little shakey when the car is cold but its nice and smooth after it has warmed up. I get 12 PSI of boost.

It also depends on you idle I think. I know that at around 750rpms my vacume is about 15 but at 900 or so rpms its closer to 20. You vacume will change with rpms so unless we all have the same idle I think we're comparing apples to oranges.

Here is my vacume readings:
750rpm - 15
about 900 rpm - 20
driving and take foot off gas - 20

The car runs real strong and has a rock solid smooth idle

Later,

Yup, vacuum is definately affected by your idle. My idle is set at around 850 and I get around 16 and it increases as I get closer to 1000 rpm. Once you go past a certain rpm, I think around 1000 rpm, the vacuum will then start to decrease.

On my old engine with 74000 miles on it (with intake, dp, and cb) I got a 16-18 vacuum reading. Dave at KDR told me with my new street-ported engine I would see around 15 and as it broke in I should see 18. I've seen 19-21 reading at about 750 rpms and it wasn't dropped any and I'm around 1000 miles - not bad - hope I can keep that kind of reading though