vaccum leak possible?? only getting 8-10psi of vac

[jdunbar10]

heya im having a problem with my car and only getting about 8-10 psi of vac

whats the easyest way to test for vac leaks since im already pulsating on rpms its nto staying still and i have replaced the cas already

 

[DSMunknown]

There's no such thing as "PSI of vacuum". Inches of mercury (also known as inHg) is what you're asking about.


Inch of mercury - Wikipedia, the free encyclopedia


As to your question, buy or makes your own boost leak tester. Also, search through the forums for "soapy water". Some good stuff to consider when narrowing down boost leaks. Did I mention easy and cheap as well? Well, now I did.


http://www.machv.com/macvleaktes.html
http://www.dsmtuners.com/forums/new...se-troubleshoot-boost-leak-tester-merged.html

 

[jdunbar10]

There's no such thing as "PSI of vacuum". Inches of mercury (also known as inHg) is what you're asking about.


Inch of mercury - Wikipedia, the free encyclopedia


As to your question, buy or makes your own boost leak tester. Also, search through the forums for "soapy water". Some good stuff to consider when narrowing down boost leaks. Did I mention easy and cheap as well? Well, now I did.


Mach V Leak Tester
http://www.dsmtuners.com/forums/new...se-troubleshoot-boost-leak-tester-merged.html

There's no such thing as "PSI of vacuum". Inches of mercury (also known as inHg) is what you're asking about.
potato potata same thing but i get what your saying

 

[DSMunknown]

Just giving you a friendly heads up. If yo ever said that in a car meet, you'd get snickered at.

 

[steve]

There's no such thing as "PSI of vacuum". Inches of mercury (also known as inHg) is what you're asking about.

While I'm sure he has used the wrong units there is such a thing as negative pressure since the 0 psi point is referenced to atmospheric pressure. Roughly 2 in hg is 1 psi so a normal idle vacuum of 18 in hg is about -9 psi.

 

[jdunbar10]

Just giving you a friendly heads up. If yo ever said that in a car meet, you'd get snickered at.

yeah true sorry didnt mean to sound like a ass or anything there,

 

[DSMunknown]

Suppose you can think of it that way, Steve. But I've always considered PSI in the positive realm and inHg in the negative, so to speak.

 

[steve]

Only because most of what you've come across used them in that manner.

But we splitting hairs not answering the question.
Pressure testing identifies leaks in the intake, checking the compression and cam timing helps identify if the loss in idle vacuum is due to bad sealing in the cylinders or a change in valve timing.

 

[jdunbar10]

its a brand new motor with less than 200 actual kms on it, could it be that the seals have not sat right yet??

and the base timing was set at 15 degrees just for low boost

oh and i have put in another CAS also

 

[steve]

The seals don't need any break in. Either something came loose or somebody F'ed up the build. Time to take it apart and fix the problem.

Your base timing needs to be 5* BTDC following the procedure in the FSM.

Since you have cams in the car the low vacuum might be from that, also the vacuum varies by altitude, It looks like Edmonton is about 2100 ft so there is going to be a reduction from that too.