Sr20det Low vacuum at idle..pondering

[SoguRacing]

ok guys so I had my engine rebuilt a few months back due to 2 spun rod bearings during tuning. Anyways long story short, My engine was rebuilt where it was tuned and I recently did a vacuum test and the reading was 12inHg. I know that normal reading range between 17-21inHg. So, My question is..What do I do or go about this problem? A reading that LOW would indicate either an intake manifold leak or late valve timing. So again..How would I go about the process or figuring out how to resolve this situation? Keep in mind that I haven't modified anything since the rebuild. Stock rebuild with hks step 1 256 cams...very mild and shouldn't cause low vacuum. There isn't enough valve overlap at idle. Any Ideas? Should I take off the valve cover and see if the timing marks line up???

[slider2828]

I haven't done a vacuum test, but on my boost controller it only stays at about -7psi or so.... I have 264HKS Step1s.... But yah my vacuum is low too, but I think it could be piston design and ring seals and maybe head gasket.... BUt I am just thinking...

[clark]

have you noticed a change in gas mileage?

i don't know if you saw this, but i googled "low vacuum at idle"

http://www.international-auto.com/fiat-lancia-tips-on-reading-gauges/tips-on-reading-gauges-vacuum-gauges.cfm

looks like a good resource. they mention that high performance cams will lower your vacuum. plus when you did your rebuild, did you use a thicker head gasket? which would cause lower compression.

[smelly240]

-7in/hg is pretty low for having step 1 264s/

Is your boost controller giving you it in metric?

[slider2828]

For me no... not really, depends hahaha!!!

If I step on it, I might get like 12 MPG lol.... But I was cruising to LA and back and I got like 22MPG. But I get like crazy torque and hp.... so eh depends how you drive. But normally, no not a decrease in MPG, maybe a little, 1 to 2 miles tops if driving civilized.

[slider2828]

What is metric? lol.... its in PSI.... did conversion and that is 14.3 in/hg

[SoguRacing]

i do have a thicker headgasket. 1.1mm compared to the stock .8mm. I wouldn't think that would actually cause the vacuum to drop so significantly. by the way, the cams are hks step 1 256 not 264.

[slider2828]

Yah it should not that bad..... Leak down test might tell you something and also do a piping tester... See if you have any leaks.

[Muad-Dib]

any news about the solution?