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VAC PUMP
#1533146
11/13/13 11:32 PM
11/13/13 11:32 PM
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Joined: Jan 2006
Posts: 246
ohio
dragon
OP
enthusiast
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OP
enthusiast
Joined: Jan 2006
Posts: 246
ohio
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Have w8 with vac pump when at a idle it has 68 oil psi but at 7000 it drop to 30 oil psi this is at 13 inch of vac this motor has a belt drive oil pump if I unhook vac pump it hold 68 oil psi anyone ever have this problem or is this the norm with this set up THANKS
Last edited by dragon; 11/14/13 01:07 AM.
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Re: VAC PUMP
[Re: dragon]
#1533148
11/14/13 01:08 AM
11/14/13 01:08 AM
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Joined: Jan 2006
Posts: 246
ohio
dragon
OP
enthusiast
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OP
enthusiast
Joined: Jan 2006
Posts: 246
ohio
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Re: VAC PUMP
[Re: dragon]
#1533151
11/14/13 02:11 AM
11/14/13 02:11 AM
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Joined: Dec 2004
Posts: 134
Closest Race Track
WH23H6
member
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member
Joined: Dec 2004
Posts: 134
Closest Race Track
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Quote:
WET with a swing pick up 8 qt of oil in pan and this is on the dyno
Hey,
Had the exact same problem.... 572 hemi... wet sump... older Milodon oil pump...had a constant 80psi until I added my vac pump. All of a sudden, I would drop to 20psi... after asking the same question, I was told the oil pump was weak. It couldn't over come the vac. The 2 pumps fight each other! I was sceptical but had no where else to look. I installed a new Ray Barton oil pump and never looked back... cured it! This is of course assuming that all of your tolerances are in order. Now have over 100psi at 7000rpm right through the stripe... only dropping briefly upon lifting at the end..
I know that many of you will feel that "excessive" oil pressure is not necessary and HP robbing... to each is own... I'm old school and believe that more is better. I'll give up some HP to extend the bearings and protect my investment. My Hemi runs 9.0s...148MPH... 3400lbs.. Just pulled the #3 bearing cap..(after 65 hard runs this year) no signs of wear ... it will be re-torqued and go another 60 to 80 runs next year! Gotta love fully grooved bearings...over 100psi and Brad Penn straight 40 oil...
Many thanks to the intelligent, experienced replies I have received on this board.. as well as the "open" ear of my good friend Tim Banning (For Hemis Only) engine builder has kept my racing hobby alive and well.
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Re: VAC PUMP
[Re: WH23H6]
#1533152
11/14/13 03:46 AM
11/14/13 03:46 AM
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Joined: Jan 2003
Posts: 19,363
Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,363
Las Vegas
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I would be looking at the oil pump as well. As fo rthe PSI thing. I run more than what oyu ahve posted and have for years. My bearings alway slook new as well and am also a Brad Penn user, although 10w30
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: VAC PUMP
[Re: Al_Alguire]
#1533153
11/16/13 01:00 AM
11/16/13 01:00 AM
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Joined: Dec 2004
Posts: 134
Closest Race Track
WH23H6
member
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member
Joined: Dec 2004
Posts: 134
Closest Race Track
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Quote:
I would be looking at the oil pump as well. As fo rthe PSI thing. I run more than what oyu ahve posted and have for years. My bearings alway slook new as well and am also a Brad Penn user, although 10w30
Its funny... when talking to some pro-mod guys.. it seems that SUPER high oil pressure is the only way to make things live! Anything with over 900 lift cams need mega oil pressure... works for me... I not one to argue with success.. High vac numbers seem to cure any leaks caused by high oil pressure numbers... seems like a win / win to me !
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Re: VAC PUMP
[Re: dragon]
#1533155
11/16/13 11:32 PM
11/16/13 11:32 PM
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Joined: Feb 2008
Posts: 452
Monrovia, So-Cal, USA
racerhog
mopar
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mopar
Joined: Feb 2008
Posts: 452
Monrovia, So-Cal, USA
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Try Slowing the Pump Speed Down.. Or lower the Vacuum to 10 or 9 in.. But If it was not a week pump. It might not have enough oil to cover the system or the wrong size inlet to the pump are possible... 
Last edited by racerhog; 11/16/13 11:43 PM.
Bob(Cowboy)Hogan
Monrovia So-Cal
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Re: VAC PUMP
[Re: racerhog]
#1533156
11/18/13 11:32 PM
11/18/13 11:32 PM
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Joined: Dec 2004
Posts: 134
Closest Race Track
WH23H6
member
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member
Joined: Dec 2004
Posts: 134
Closest Race Track
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Quote:
Try Slowing the Pump Speed Down..
Or lower the Vacuum to 10 or 9 in..
But If it was not a week pump. It might not have enough oil to cover the system or the wrong size inlet to the pump are possible...
Shouldn't have to slow the vac pump down.... you need 14 to 16 inches to make it worth while..if the oil pump is up to the task... make sure the catch can is not filling up...could be the wrong place to draw from. I draw from both sides... splitting the pressure but keeping the volume the same..
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Re: VAC PUMP
[Re: AndyF]
#1533158
11/19/13 01:07 AM
11/19/13 01:07 AM
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Joined: Mar 2006
Posts: 9,835
MI, usa
dvw
master
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master
Joined: Mar 2006
Posts: 9,835
MI, usa
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A pump will become more and more inefficient as the pressure on the inlet side is lower. Think of how well a fuel pump would work with no vent? My bet is the internal design of your pump is affected by less positive pressure on the inlet side than other style pumps. It could be by design or excessive internal clearance of your pump. Also the required volume of your engine could have the relief valve almost completely closed when supplying the 68psi@7000 w/o the vacuum pump. When you remove the positive atmospheric pressure on the inlet side, the pump can no longer keep up equaling less pressure. I would say a different style pump or decreased internal leakage. My 2 cents Doug
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