A/C vacuum pump (venturi style) question

[Wile E Coyote]

I've put this in tools, as it's not vehicle-specific.

Anyway, in gathering the supplies to do a moderate rehab on the cruiser's AC system, I picked up an el-cheapo venturi-style vac pump.
I tested the setup today and am questioning the adequacy of vac achieved when accounting for moderate elevation (I'm at roughly 3,700 ft). I don't think I'll see 29.95 in.Hg at 3,700 ft elevation. I believe my best case should be around 26.2 inHg. How does that sound to those in the know? Regardless, I don't think I can get there using the venturi vac pump. I saw just about 23.5 in Hg using two separate gauges. I'll be heading to the part's store to rent a real vac pump.
Edit: Forgot to mention the above tests were directly from vac pump to gauges, not on-vehicle.

 

[cruiser88]

I see those numbers alot. Its damn hard to get a perfect vaccum...............you will not see it anyway.

Dont beat your head over it. Its most important to get any and all moisture out and change the oil in that pump.

 

[Wile E Coyote]

I fingered you'd have something to add, Crazy me boy. Thanks pal. Of course, getting all the moisture out is why I'm sweating the numbers in the first place, hehe.

 

[cruiser88]

sorry I aint no help

I fingered you'd have something to add, Crazy me boy. Thanks pal. Of course, getting all the moisture out is why I'm sweating the numbers in the first place, hehe.

 

[Wile E Coyote]

Update: I picked up a loner vane-type vac pump, and am seeing about 26 in Hg straight from pump to gauges. Mo betta!

 

[Pin_Head]

You talking about an air venturi or water venturi pump? Water venturi pumps can pump down to about 25 microns, depending on water velocity. This is good enough for A/C. Vane type oil pumps can pump below 1 micron. We use a lot of vane type pumps at work and throw them away when they can't pump below 10 because rebuilding costs more than a new one.