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Oil preasure / Vacume pump question #1228883 05/07/12 02:03 PM 05/07/12 02:03 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	Hey guys, Heres a strange one maybe can shed some light on.... Freshened my engine over the winter..(Hemi) and added a couple of things...Vacume pump and a remote system 1 filter... When the engine is fired and running now...I noticed that the oil preasure is erattic...from 85 on start up...down to 60, 40 and finally none after a minute or so...at first I thought the relief valve was acting up...so we checked it and no problems.. After trying a few things over the weekend...I discovered that if I unhook the Vacume pump the oil preasure stays put at 85lbs...going to 80lbs idling, warm.... same as its been for like 10 years! Gauge shows only 6 inches of vacume when the pump is hooked up... No getting around it...hooking up the vabume pump is the culprit..but why? ( I also remade my 2 supply lines from the pan to the pump on the off chance that they were internaly collapsing...no change...) Anybody ever seen this before?? Thanks,

Re: Oil preasure / Vacume pump question [Re: WH23H6] #1228884 05/07/12 02:48 PM 05/07/12 02:48 PM
Joined: Jul 2010 Posts: 2,091 Delray beach, Florida P Performance Only top fuel
Performance Only top fuel P Joined: Jul 2010 Posts: 2,091 Delray beach, Florida	i've never seen that happen with only 6" of vacuum. what size oil pan are you running? i've seen hemi's that leak around the intake manifold internally that creat a lot of vacuum in the crankcase16-18" and still not have that problem. are you using steel braided lines to the pump? machine shop owner and engine builder

Re: Oil preasure / Vacume pump question [Re: WH23H6] #1228885 05/07/12 03:26 PM 05/07/12 03:26 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	I have seen a vac pump give a slightly lower oil pressure reading but nothing like your saying

Re: Oil preasure / Vacume pump question [Re: MR_P_BODY] #1228886 05/07/12 04:28 PM 05/07/12 04:28 PM
Joined: Mar 2006 Posts: 9,910 Eighty Four, PA B G Racing master
B G Racing master Joined: Mar 2006 Posts: 9,910 Eighty Four, PA	If your engine is sealed up real good sometimes the vacume pump will pull the oil pressure away.Try and put an open style breather on one valve cover and your problem will go away.Then restrict the breather or just make sure you vacume pump is pulling at least 5# [IMG]http://i430.photobucket.com/albums/qq21/ajcasini/max_zpsdppwd9km.jpg[/IMG]

Re: Oil preasure / Vacume pump question [Re: Performance Only] #1228887 05/07/12 04:30 PM 05/07/12 04:30 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	Quote: i've never seen that happen with only 6" of vacuum. what size oil pan are you running? i've seen hemi's that leak around the intake manifold internally that creat a lot of vacuum in the crankcase16-18" and still not have that problem. are you using steel braided lines to the pump? Its a custom 10 Quart pan...been on the engine for 10 years...swinging pickup with duel lines...Milodon... # 12 braided to the pump... No intake leaks...

Re: Oil preasure / Vacume pump question [Re: B G Racing] #1228888 05/07/12 04:32 PM 05/07/12 04:32 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	She is sealed up pretty tight... Sounds like its worth a try....project for tonight!

Re: Oil preasure / Vacume pump question [Re: WH23H6] #1228889 05/07/12 04:42 PM 05/07/12 04:42 PM
Joined: Mar 2006 Posts: 9,910 Eighty Four, PA B G Racing master
B G Racing master Joined: Mar 2006 Posts: 9,910 Eighty Four, PA	Quote: She is sealed up pretty tight... Sounds like its worth a try....project for tonight! [/quote Give it a try,it worked on a few we have running out of BGR.68WV Charger(Pap and Allen Ross) had the same problem. [IMG]http://i430.photobucket.com/albums/qq21/ajcasini/max_zpsdppwd9km.jpg[/IMG]

Re: Oil preasure / Vacume pump question [Re: B G Racing] #1228890 05/07/12 04:57 PM 05/07/12 04:57 PM
Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey J jamesc master
jamesc master J Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey	Quote: If your engine is sealed up real good sometimes the vacume pump will pull the oil pressure away. Bob not being argumentative but i'd like to know exactly what you mean by this? imho the only way pulling a mild vacuum on the crankcase could possibly cause the problem you're having is by causing the pump to cavitate and/or cause air to be pulled into the suction side of the pump. make sure the suction side integrity is good and remember this side is under vacuum even without the vacuum pump so leaks are not always readily apparent. you should definitely be able to run 6" without issue. if you have a vacuum relief valve where is it located, what oil pump are you running?

Re: Oil preasure / Vacume pump question [Re: jamesc] #1228891 05/07/12 05:48 PM 05/07/12 05:48 PM
Joined: Apr 2004 Posts: 1,056 Mt.Vernon IL Twin Turbo Mower super stock
Twin Turbo Mower super stock Joined: Apr 2004 Posts: 1,056 Mt.Vernon IL	Keeping the oil in the top end too much maybe with the pump running not allowing it to drain back fast enough?

Re: Oil preasure / Vacume pump question [Re: B G Racing] #1228892 05/07/12 05:50 PM 05/07/12 05:50 PM
Joined: Jul 2010 Posts: 2,091 Delray beach, Florida P Performance Only top fuel
Performance Only top fuel P Joined: Jul 2010 Posts: 2,091 Delray beach, Florida	Quote: If your engine is sealed up real good sometimes the vacume pump will pull the oil pressure away.Try and put an open style breather on one valve cover and your problem will go away.Then restrict the breather or just make sure you vacume pump is pulling at least 5# i think you mean 5", not 5#,(60") right? machine shop owner and engine builder

Re: Oil preasure / Vacume pump question [Re: jamesc] #1228893 05/07/12 11:00 PM 05/07/12 11:00 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	Quote: Quote: If your engine is sealed up real good sometimes the vacume pump will pull the oil pressure away. Bob not being argumentative but i'd like to know exactly what you mean by this? imho the only way pulling a mild vacuum on the crankcase could possibly cause the problem you're having is by causing the pump to cavitate and/or cause air to be pulled into the suction side of the pump. make sure the suction side integrity is good and remember this side is under vacuum even without the vacuum pump so leaks are not always readily apparent. you should definitely be able to run 6" without issue. if you have a vacuum relief valve where is it located, what oil pump are you running? This is what I was thinking...but I cant see where this is happening.... I pulled the pump tonight as well as the oil pan...no obvious problems... Its a Milodon pump, aluminum, duel external line pump. Custom oil pan..milodon swinging pickup..Vac pump relief valve is located on the top of the pump and is adjustable...separate gauge in the car...6" at 1200rpm Un-screw the adjuster so there is no vabume pump vacume and it sits at 85lbs oil presure..at 1200rpm...no fluctuation....screw the adjuster in so there is 6" of vacume and the oil preasure goes away! Seeing as how Im looking to get 14" at 7000rpm... its kinda freaked me out!!

Re: Oil preasure / Vacume pump question [Re: WH23H6] #1228894 05/08/12 12:07 AM 05/08/12 12:07 AM
Joined: Oct 2011 Posts: 3,036 bean town ....Ca W WHITEDART master
WHITEDART master W Joined: Oct 2011 Posts: 3,036 bean town ....Ca	sounds like a small leak in between the oil pick up and the oil pump that the vaccume from the pump can get to ? In the 8s N/A.with Brett miller W8's 5.07 at 133 at 2700lb

Re: Oil preasure / Vacume pump question [Re: WH23H6] #1228895 05/08/12 12:39 AM 05/08/12 12:39 AM
Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey J jamesc master
jamesc master J Joined: Jan 2003 Posts: 5,875 communist bloc of new jersey	i'm not sure if i can explain this "guess" correctly but... the milodon system feeds the rotors from both sides and "if" it's pulling air in somewhere (it would only take a little) it could cause the pump to become somewhat air bound. although this really shouldn't happen with a positive displacement type pump as opposed to centrifugal. there's the possibility that once the pump gets a little air in it, it may not really want to start pumping until it's oil filled again. i'm assuming it's the standard milodon setup which usually uses an AN type male union that threads into the pickup then the suction lines thread onto that. imho these fittings need to be sealed on both the inside and outside of the pan. i cut up some washers out of neoprene sheet though there are washers sold specifically for this. you have the vacuum relief mounted in the correct spot. sure sounds like an oddball problem but i would think that in some way it has to be getting air into the suction side. if the pump is worn somewhat it could aggravate the problem. this is the aluminum milodon pump that has the external feed fitting threaded into the side of it and the cover with the second feed in it?

Re: Oil preasure / Vacume pump question [Re: WH23H6] #1228896 05/08/12 01:07 AM 05/08/12 01:07 AM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Its a custom 10 Quart pan...been on the engine for 10 years...swinging pickup with duel lines...Milodon... # 12 braided to the pump... No intake leaks... You could be sucking the O-rings in the pick up free by a little and sucking in air there IF that point is above the oil level... they dont have much drag on the O-rings so the pick up can pivot... the problem pretty much has to be on the suction side of the pump

Re: Oil preasure / Vacume pump question [Re: MR_P_BODY] #1228897 05/08/12 06:38 AM 05/08/12 06:38 AM
Joined: Mar 2006 Posts: 9,886 MI, usa dvw master
dvw master Joined: Mar 2006 Posts: 9,886 MI, usa	Is there actually no pressure or is the gauge wrong? It's been mentioned before that a vacuum pump acts on the gauge diaphragm. Doug

Re: Oil preasure / Vacume pump question [Re: dvw] #1228898 05/08/12 08:09 AM 05/08/12 08:09 AM
Joined: Apr 2004 Posts: 1,056 Mt.Vernon IL Twin Turbo Mower super stock
Twin Turbo Mower super stock Joined: Apr 2004 Posts: 1,056 Mt.Vernon IL	What block are you using? I still think you are sucking the pan dry with the pump running and its not letting the oil drain back properly through the valley. My indy block did the same thing when I let too much oil go to the top end. I did not have restrictors in the oil lines to the heads. Once I put some in my oil pressure was fine. The indy block has small oil holes for drain back. With a vacuum pump running and air being drawn from the crank case through the valley it could restrict drain back. For now I would do what bg said and put a breather on the other valve cover. Last edited by Twin Turbo Mower; 05/08/12 08:10 AM.

Re: Oil preasure / Vacume pump question [Re: Twin Turbo Mower] #1228899 05/08/12 08:39 AM 05/08/12 08:39 AM
Joined: Mar 2006 Posts: 9,910 Eighty Four, PA B G Racing master
B G Racing master Joined: Mar 2006 Posts: 9,910 Eighty Four, PA	5" is correct,and this has happened and it has been corrected by the method I described.On Dave Ross' 540" wedge the pressure went to 0,he called the pump manufacture and they told him the same thing.He vented the engine and his oil pressure was rock solid and his pump was set for 5" Last edited by B G Racing; 05/08/12 08:42 AM. [IMG]http://i430.photobucket.com/albums/qq21/ajcasini/max_zpsdppwd9km.jpg[/IMG]

Re: Oil preasure / Vacume pump question [Re: Twin Turbo Mower] #1228900 05/08/12 05:19 PM 05/08/12 05:19 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	Quote: What block are you using? I still think you are sucking the pan dry with the pump running and its not letting the oil drain back properly through the valley. My indy block did the same thing when I let too much oil go to the top end. I did not have restrictors in the oil lines to the heads. Once I put some in my oil pressure was fine. The indy block has small oil holes for drain back. With a vacuum pump running and air being drawn from the crank case through the valley it could restrict drain back. For now I would do what bg said and put a breather on the other valve cover. Its the MP Mega block....stage 5 millenium heads....would putting a breather on the opposite valve cover just not defeat the purpose of the Vacume pump? I can't help but think is got to be a leak on the suction side of the oil pick up somewhere were in the vacume area... I took off the pan and pickup last night...couldnt see anything....the o-rings between the pickup and pan where nice and tight....All I know for sure is Im not nuts ! Its happening....

Re: Oil preasure / Vacume pump question [Re: dvw] #1228901 05/08/12 05:21 PM 05/08/12 05:21 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	Quote: Is there actually no pressure or is the gauge wrong? It's been mentioned before that a vacuum pump acts on the gauge diaphragm. Doug I have a Mechanicle gauge as well as a 30lb trigger for my pro oil light...gauge hits 30 and the light is on....both devices are in separate sides of the block....

Re: Oil preasure / Vacume pump question [Re: B G Racing] #1228902 05/08/12 05:26 PM 05/08/12 05:26 PM
Joined: Dec 2004 Posts: 134 Closest Race Track W WH23H6 OP member
WH23H6 OP member W Joined: Dec 2004 Posts: 134 Closest Race Track	Quote: 5" is correct,and this has happened and it has been corrected by the method I described.On Dave Ross' 540" wedge the pressure went to 0,he called the pump manufacture and they told him the same thing.He vented the engine and his oil pressure was rock solid and his pump was set for 5" So did he restrict the vent just enough to still build Vacume? Do you know how much over all Vacume it made at high RPM? I was looking for about 13" at 7000.... I understand that any more than 13 or 14 will start to pull oil off bottom end parts...wrist pins and such... The grief we go through just to try and put an "8" something on the window!!

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