When I'm at idle, my boost gauge reads 20 VAC. Now I was reading, and people said theirs was 10-15 vac on Idle. Now I guess I'll ask, is that normal, or am I in trouble? Just curious...I'm sure my gauge works, because it reads my boost at 7PSI which is correct.

 

If I'm wrong someone will correct me but i'm under the impression that a GOOD motor will pull MORE than 15 (is it PSI or mm/hg?) and the normal range is 10-15 (mm/hg or psi, I can't recall)

 

it's in mm/hg, and that would be neat, since when I got a compression check, it was supposedly in the 60's! I figured that was damn near dead numbers, and this was a few months back. My engine isn't flooding, shows no signs of power loss, no problems on starts...I just don't know!

I figured I'd ask, and see what everybody else had to say.

 

20 VAC is a perfect engine with good compression.

15 VAC is either a tired engine or a street ported engine

10 VAC is an aggressive port engine.

EDIT: Woohoo Cyber, you're in my sig!

 

Was the compression taken while the engine was hot or cold?

 

The compression was taken while the engine was hot. I got done driving it about 3-5 minutes. So it wasn't smokin, but you get the idea.

So, you're saying that since I get "20" vac on my boost gauge, that I actually have good compression!? :O I'm stoked if so.
And yeah, ahhaa, the sig is funny. Because it's so true....

 

It's "mmHg" which translates to millimeters of vacuum in reference to mercury.
Not "mm/Hg"... :P

18 mmHg is what a "healthy", stock port motor would typically see.

What is your idle speed?
Spec is 750RPM + / - 50RPM.
(Higher than spec) idle speed can increase idle vacuum.
Is your ignition timing stock spec?
Adjustment of ignition timing outside of stock spec can affect idle vacuum.

What brand gauge is this?
Autometers (or almost anything cheap) can be inaccurate.


-Ted

 

Well, looks like i have a cheap gauge And my idle speed is anything from 750-1300....Not sure why it fluctuates like that, so my excuse is *it's a rotary*. It doesn't just bounce constantly, it's always a steady idle, just whenever I push the clutch in/take it out of gear/etc is when it his some other idle.l So lack of bouncing is good, right? :p As for the timing, I've not touched it, don't know if it was touched, wouldn't be able to find out if it was touched...

 

mine is around 12 on the vac. guage and i have a healthy engine....

:S

 

I suspect to have a "not so healthy" engine. I read 17x,xxx on my odo. I'm guessing it got rebuilt once, but it was probably prior to 100k miles. So that means it SHOULD be on it's last leg, since I doubt it wasn't driven nice before I got it....well, I guess I should just follow my plan to get a rebuild/port anyway. I was just hoping to delay it a little more. I'm still trying to save my money, and I'm not sure how much a rebuild/port/reinstall costs...I'm hoping it's only around 2k..