Re: Oil preasure / Vacume pump question
[Re: WH23H6]
#1228884
05/07/12 02:48 PM
05/07/12 02:48 PM
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Joined: Jul 2010
Posts: 2,091 Delray beach, Florida
Performance Only
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top fuel
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Delray beach, Florida
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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
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Re: Oil preasure / Vacume pump question
[Re: Performance Only]
#1228887
05/07/12 04:30 PM
05/07/12 04:30 PM
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Joined: Dec 2004
Posts: 134 Closest Race Track
WH23H6
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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...
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Re: Oil preasure / Vacume pump question
[Re: WH23H6]
#1228889
05/07/12 04:42 PM
05/07/12 04:42 PM
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Joined: Mar 2006
Posts: 9,910 Eighty Four, PA
B G Racing
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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.
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Re: Oil preasure / Vacume pump question
[Re: B G Racing]
#1228890
05/07/12 04:57 PM
05/07/12 04:57 PM
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Joined: Jan 2003
Posts: 5,875 communist bloc of new jersey
jamesc
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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?
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Re: Oil preasure / Vacume pump question
[Re: jamesc]
#1228893
05/07/12 11:00 PM
05/07/12 11:00 PM
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Joined: Dec 2004
Posts: 134 Closest Race Track
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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!!
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Re: Oil preasure / Vacume pump question
[Re: WH23H6]
#1228894
05/08/12 12:07 AM
05/08/12 12:07 AM
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Joined: Oct 2011
Posts: 3,036 bean town ....Ca
WHITEDART
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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
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Re: Oil preasure / Vacume pump question
[Re: dvw]
#1228898
05/08/12 08:09 AM
05/08/12 08:09 AM
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Joined: Apr 2004
Posts: 1,056 Mt.Vernon IL
Twin Turbo Mower
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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.
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Re: Oil preasure / Vacume pump question
[Re: Twin Turbo Mower]
#1228900
05/08/12 05:19 PM
05/08/12 05:19 PM
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WH23H6
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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....
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Re: Oil preasure / Vacume pump question
[Re: dvw]
#1228901
05/08/12 05:21 PM
05/08/12 05:21 PM
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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....
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Re: Oil preasure / Vacume pump question
[Re: B G Racing]
#1228902
05/08/12 05:26 PM
05/08/12 05:26 PM
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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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