Normal for vacuum pump to cause lower oil pressure
04-18-2008, 07:27 PM
#1
Normal for vacuum pump to cause lower oil pressure Figured I would post in here since you guys might know more about this. Since I installed my GZ vacuum pump I have noticed lower oil pressure both at idle and while driving. I tried to watch the gauge as I got on it wot on the street and it seems to only want to go as high as 50 on both the stock and autometer guages. Is 50 enough when taking over 6k? I was always under the impression 10 psi for every 1k rpm?? Thanks for the help.
04-18-2008, 07:55 PM
#5
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I've used one for 10 plus years, always loose some pressure. That's why on the slow car,
I have the valve set up for extra pin oiling. Before I towed up & back from line, my engine guy made me build it.
Open for driving, warm up, burn out. Closed for pass. Good luck.
.
I've used one for 10 plus years, always loose some pressure. That's why on the slow car,
I have the valve set up for extra pin oiling. Before I towed up & back from line, my engine guy made me build it.
Open for driving, warm up, burn out. Closed for pass. Good luck.
.
04-19-2008, 09:28 AM
#6
Being that pressure is an indicator of resistence to flow, the addition of a vac system, will reduce this resistence. Thus the lower psig. IE: oil flow into a pressurized container, [the oil pan], takes more psi than the flow into a partially evacuated container.
As mentioned, get the vac too high, and you'll run into problems w/ wrist pin oiling, etc. [Unless the clearances are set considering the vac system use.]
As mentioned, get the vac too high, and you'll run into problems w/ wrist pin oiling, etc. [Unless the clearances are set considering the vac system use.]
04-19-2008, 01:14 PM
#7
Being that pressure is an indicator of resistence to flow, the addition of a vac system, will reduce this resistence. Thus the lower psig. IE: oil flow into a pressurized container, [the oil pan], takes more psi than the flow into a partially evacuated container.
As mentioned, get the vac too high, and you'll run into problems w/ wrist pin oiling, etc. [Unless the clearances are set considering the vac system use.]
As mentioned, get the vac too high, and you'll run into problems w/ wrist pin oiling, etc. [Unless the clearances are set considering the vac system use.]
So you are saying I am better off with the lower oil psi and the vacuum pump set at a safe setting? The oil psi was only 50 at 6k at wot. Would this be the same as 65psi without the pump but a pressurized oil pan not breathing properly? Just want to have a safe setup and not hurt anything.
Last edited by 03 BUSA; 04-20-2008 at 11:20 AM.
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04-22-2008, 06:29 PM
#12
That would be great, I'll host 'em and post 'em. SpearZ28@Gmail.com
I've been thinking about doing a vacuum system on mine. I make 55-60psi at idle though, so I don't think I'll to worry about my pressure dropping at idle lol.
I've been thinking about doing a vacuum system on mine. I make 55-60psi at idle though, so I don't think I'll to worry about my pressure dropping at idle lol.
04-22-2008, 08:09 PM
#14
As posted above, you need to have a vac guage & watch at all RPM's to make sure it does NOT pull more than 12-14 inches or it pulls the oil off the wrist pins & some from the main journals. What weight & kind of oil are you running? The vac relief valve should be in the opposite valve cover as the pump draws vac from. We run belt driven pumps on all our alky motors & have for years....first the Moroso & then Aerospace (as they sponsor us). The higher the RPM's the higher the negative pressure...so setting it at 5-6 at 3k should be safe, but you won't know until you get a guage to watch it through the run.
Here is a pic...hard to see, but the pump draws from the left side valve cover & the relief valve is on the right (not visable) We use -12 lines for the amount of flow & the catch can needs to be emptied every 3-4 passes depenging on the humidity.
(Alky is a sponge for moisture).
Here is a pic...hard to see, but the pump draws from the left side valve cover & the relief valve is on the right (not visable) We use -12 lines for the amount of flow & the catch can needs to be emptied every 3-4 passes depenging on the humidity.
(Alky is a sponge for moisture).
Last edited by TLewis4095; 04-22-2008 at 08:22 PM.
