Hey am just wondering if any one can tell me what a standard reading for vaccuum would be on a gauge that reads in IN HG.

Mine is reading 13.5 inhg at idle of round 800 rpm.

as far as i know a ported engine will have lower readings. but um pretty sure that mines not ported.. unwilling to disassemble engine to find out. he he maybe there is a way to tell if ported without dissembling ???


But anyway after looking at other cars and there gauges i am coming to the assumption that i might have a leak.

any help is appreciated.

Thanks mark

 

compression test it and see what that turns up.

 

Hows it.

So your saying to compression test the engine and that will let me know if it is ported. or that i should compression test the vaccuum lines to check for a leak???

Thanks mark

 

All vacuum leaks I have had caused high idle.

 

compression test it and see what that turns up.[QUOTE]

What he's saying is that low compression will likely show up as a low vacuum reading at idle. If your compression is good you may have a ported motor. I guess you could pull the manifold and find someone with a bore o scope to take a peek.

 

13.5" is pretty low, even for a ported engine. That sounds more like a relatively weak motor, or a bad connection of the vacuum line running to the boost gauge. Those cheesy ferrules and nylon hoses that come with Autometer gauges are notorious for leaking.

A vacuum leak will typically give you a *higher* idle.

A compression test on the motor will let you know how healthy the motor is.

Dale

 

Thanks guys. computer has been out of action so hence the late reply.
Will sort out a compression test. although the motor was only re built 10,000kms ago.
Thanks mark.

 

Have compression tested motor front and back i am getting an 75 to 80psi reading.

Is this ok for a rebuilt motor?
Thanks marks

 

sorry... but no. that's very low . that's about 5.5 kg/cm^2, you want to be at least 6.0 (for a worn engine). a new, healthy engine should be around 8.0.