Since putting my new engine in, I do not have enough vacuum now to operate the heater control valve now. I'm assuming that the lack of vacuum is due to my cam. At idle it's only pulling about 13" of Hg.

Does anyone know of a simple way to remedy this problem? Thanks

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Black 88 GTA L98
New engine is in!
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back
E.T.F.A Member #11

 

It seems to me that you have a vacuum leak. The LT4 hot cam should pull more vacuum then that. I had a leak recently that I would have never known was there had I not looked. The car was running fine. Turned out a line had come off.

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Bob '89 Formula CC350
Last(lost)Member of the Elusive Great Lakes Crew
My car's homepage

 

I'm with RCR on this one. When I was working on my a/c system, someone told me that it should still work with even about 5" vacuum. Mine had 21", and my problem was not a leak, but check all your connections... Good luck to ya.

KAM

 

A leak may be my problem, but there's no way that the heater control valve will operate of 5 in of Hg. My heater control valve is getting vacuum right now, just not enough to open it up apparently. If I pull the vacuum hose out of it and suck on it the valve will open, so it does function, just needs more vacuum (more vacuum - does that make sense )apparently.

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Black 88 GTA L98
New engine is in!
ZZ4 bottom end, Edelbrock 6085 heads, LT4 HOT cam, GMPP 1.6 RR's, ported stock TPI, SLP 1 3/4" headers, no cat, Dynomax cat-back
E.T.F.A Member #11

[This message has been edited by Scott 88 GTA (edited November 21, 2000).]

 

Scott,

More vacuum, lower absolute pressure, greater suction - however you want to look at it, you ain't got enough of something or have too much of the wrong thing (huh?).

Adapt your vacuum gauge to the small control line size and measure vacuum at the control hose. It's possible that the HVAC control valve is losing its silicone sealant and not applying enough vacuum to actuate the controls properly. Instead of freezing your nards off, put a nylon wire tie on the valve belcrank and open it up. Diagnose the problem, then cut the wire tie.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Vader, I didn't hook the gauge up to the control hose, but one thing I did try was running a vacuum line straight from the plenum to the control valve, this didn't even provide enough vacuum to open it; so I doubt the problem is in the HVAC system. I'm going to look for vacuum leaks tomorrow evening.

Any more ideas?