More cam = less vacuum at idle??????

[Dolby109]

So I just finished putting in a new SR20DET in my 240, and this engine has stage II cams in it.
Without too much trouble I got it running and idling decently, however when I looked at my boost gauge I noticed that it was only running ~10-12psi vacuum.
My old SR with stock cams ran at about 18-20 if memory serves.

So I am wondering if I have some vacuum leak somewhere (this car has far too many vac lines on the manifold) or is it just the cam causing this?

[jr_ss]

The cam can and in most cases will cause lower vacuum.

[S@nt0s]

dont worry its just the higher profile cam
my car idles with about 5-10 vac

[Dolby109]

Thanks!
So now I have another question.
At first the idle was too low for the new cam, so I adjusted it slightly to 900 which seems to idle great. However I took it out for a short drive and the car dies every time I am slowing down (with clutch in) unless I feather the gas.
Do I need more idle, or is there any other way (besides a tune) to fix this?

[S@nt0s]

your idle/vac map needs tuning for the cams

[codyace]

Did you verify timing and idle with this? Typcically when people install cams they loose timing correctness and also have the idle way to low...both of which cause poor vacuum.

My car with S3's pulls 17hg of vacuum, not very far off stock.

[Dolby109]

So, what approx should my idle and timing be set to?
Can I just make minor adjustments to the timing and use the vacuum as a guage for when it is close to correct?
The motor came with the angle sensor turned all the way clockwise, so I centered it out. Like I said it does seem to idle ok, but doesn't come down from higher RPM well.

[S@nt0s]

Cam angle sensor needs to be dialed in. Set up your timing at idle

[Dolby109]

And as a reference the timing should be ...?
I have never actaully set the timing before on an SR (my old motor ran fine with what it was set at).

I am vaguely aware that you have to get a plug wire from another DOHC car and plug it into the coil to use a timing light.
As I dont have a timing light is there anyway to adjust the timing by sound, idle smoothness, or vacuum reading?

[codyace]

Originally Posted by Dolby109

So, what approx should my idle and timing be set to?
Can I just make minor adjustments to the timing and use the vacuum as a guage for when it is close to correct?
The motor came with the angle sensor turned all the way clockwise, so I centered it out. Like I said it does seem to idle ok, but doesn't come down from higher RPM well.

There are many guides on setting timing on the SR20, a google search would be the best place as it would be easier than me typing it.

Another thing to consider is your idle vacuum. While in timing mode, I'd also raise the idle a smidge to help compensate as well (bottom of IACV there is a screw)

[Dolby109]

Originally Posted by codyace

There are many guides on setting timing on the SR20, a google search would be the best place as it would be easier than me typing it.

Another thing to consider is your idle vacuum. While in timing mode, I'd also raise the idle a smidge to help compensate as well (bottom of IACV there is a screw)

Yes but I was wanting to know if the timing is different for a S2 cammed car, and what the idle should be at. I have allready adjusted to 900rpm which idles fine, but still has problems coming down from higher RPM. Is 1000, or 1100 preferable?

[cotbu]

Their installation guide should tell you what timing to set, usually stock!
As far as idle, In the text books it says to set the idle rpm to the lowest stable idle you can achieve.?!? If i followed that rule I could idle at 650rpm, but I always set Sr20's to idle at 850rpm. (I like the sound.)
I seen 1000pm to 1200rpm idles though, I never understood why. In your case, I would go over all vacuum lines and vacuum dependent equipment and make sure you have no leaks, check all sensors, then get tuned.