Oil pressure fluctuation question
#2689142
08/18/19 06:24 PM
08/18/19 06:24 PM
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Joined: Mar 2009
Posts: 2,462 Sydney,Australia
tex013
OP
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OP
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Joined: Mar 2009
Posts: 2,462
Sydney,Australia
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What are peoples thoughts on this ?
I am getting some oil pressure fluctuation just before finish line then some drop when backing off . Normally run 60-65psi wide open , is fluctuating down to 50/55ish then back up to 65 then drops to 30/35 when i lift . Comes back up after about a second or so to 45 . RPM is slowing through 4500 at this time . Motor is a Mopar big block , 505ci . It is a World iron block , Mellings HV oil pump , solid flat tappet cam . It has a Milodon road race oil pan with 8 1/2 quarts oil , Penn Grade 20/50 currently . Will be going to Royal Purple 20/50 . New motor has about 20 passes and 6-800 street miles . Vehicle is my daily driver , bracket race monthly . Oil pressure cold is 70psi , hot is 18-20 psi in gear idleing jumps to 40psi from idle to 3500 then up around 65psi . I do not have any issues in daily street/ highway running
Thinking whether I go to an Accusump . With manual valve so as only operating on race day . 45 or 55psi switch ? Sandwich adapter at oil filter. Try an extra quart of oil ? Not much room in the engine bay , 68 Satellite . .
Tex
Last edited by tex013; 08/18/19 06:26 PM.
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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Re: Oil pressure fluctuation question
[Re: tex013]
#2689146
08/18/19 06:29 PM
08/18/19 06:29 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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What are peoples thoughts on this ?
I am getting some oil pressure fluctuation just before finish line then some drop when backing off . Normally run 60-65psi wide open , is fluctuating down to 50/55ish then back up to 65 then drops to 30/35 when i lift . Comes back up after about a second or so to 45 . RPM is slowing through 4500 at this time . Motor is a Mopar big block , 505ci . It is a World iron block , Mellings HV oil pump , solid flat tappet cam . It has a Milodon road race oil pan with 8 1/2 quarts oil , Penn Grade 20/50 currently . Will be going to Royal Purple 20/50 . New motor has about 20 passes and 6-800 street miles . Vehicle is my daily driver , bracket race monthly . Oil pressure cold is 70psi , hot is 18-20 psi in gear idleing jumps to 40psi from idle to 3500 then up around 65psi . I do not have any issues in daily street/ highway running
Thinking whether I go to an Accusump . With manual valve so as only operating on race day . 45 or 55psi switch ? Sandwich adapter at oil filter. Try an extra quart of oil ? Not much room in the engine bay , 68 Satellite . .
Tex Your oil pressure doesn't make sense. You are using a 20w50 oil and only have 20 PSI hot idle pressure with a HV pump. That makes no sense. I'm not a fan of the accusump. Just another place for leaks and more plumbing.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Oil pressure fluctuation question
[Re: tex013]
#2689149
08/18/19 06:46 PM
08/18/19 06:46 PM
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Joined: Aug 2003
Posts: 43,157 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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Last edited by Cab_Burge; 08/18/19 07:21 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Oil pressure fluctuation question
[Re: madscientist]
#2689156
08/18/19 07:01 PM
08/18/19 07:01 PM
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Joined: Jan 2003
Posts: 1,237 North Central, Indiana
Roughbird72
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,237
North Central, Indiana
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Your oil pressure doesn't make sense. You are using a 20w50 oil and only have 20 PSI hot idle pressure with a HV pump. That makes no sense.
I'm running the same pump with 10W-40 and hot idle, in gear is 30-32#
72 Plymouth Roadrunner 11.08@123.25
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Re: Oil pressure fluctuation question
[Re: Cab_Burge]
#2689172
08/18/19 07:50 PM
08/18/19 07:50 PM
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Joined: Oct 2007
Posts: 4,206 New York
polyspheric
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master
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New York
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Your running out of oil in the sump I agree, something is wrong in the pan, that big a drop means the pickup head is uncovered. I suspect there may be more than one factor. What oil control measures in the pan? Do you have a picture of pan interior? Kevin Johnson at Speedtalk is very good at this stuff.
Boffin Emeritus
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Re: Oil pressure fluctuation question
[Re: AndyF]
#2689204
08/18/19 09:19 PM
08/18/19 09:19 PM
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Joined: Mar 2009
Posts: 2,462 Sydney,Australia
tex013
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OP
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thanks guys I will be racing this weekend so will try some extra oil . 20/50 . I just always have , it does sit in traffic a lot at times so just some insurance . Both this World and stock blocks for me have dropped to 20psi hot idle in gear . 900rpm , after 1 hour down the freeway to the track especially . Milodon road race pan is fully baffled and trapdoored .
Have not noticed this before with stock block , pressure movement at top end . World has full time rocker oiling and priority main oiling so may be pushing a little more up top .
Tex
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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Re: Oil pressure fluctuation question
[Re: MR_P_BODY]
#2689277
08/19/19 06:39 AM
08/19/19 06:39 AM
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Joined: Mar 2009
Posts: 2,462 Sydney,Australia
tex013
OP
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OP
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Joined: Mar 2009
Posts: 2,462
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Cab , yes mine has the stock restrictors MrP , will pull r covers and have a look . Had a chat with machine shop . Noted he used a moroso/milodon(?) relief spring . Seemed to solve similar issue with his World block . He has a spare i can grab next weekend
Tex
Last edited by tex013; 08/19/19 06:44 AM.
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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Re: Oil pressure fluctuation question
[Re: sgcuda]
#2689294
08/19/19 08:21 AM
08/19/19 08:21 AM
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Joined: Mar 2006
Posts: 9,835 MI, usa
dvw
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master
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MI, usa
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A baffle in the front of the pan may help on decell. Does it already have a rear baffle? You are experiencing pressure loss on accell as well. This tells me the pan level could very well be low. Also 20 psi at idle with 20/50 shows it needs a fair amount of volume to make pressure at higher rpm. It could be bleeding excessive oil upstairs. Less internal leakage will leave more in the pan. Does it have 8.5 qts in the entire engine or just the pan? 8.5 qts in the pan should be more than enough with proper baffling. I can run mine with 6.5 qts in the pan with no fluctuation at either end. But it has a completely different pan. Baffles, swing trap door, swinging pick-up, and a full length diamond mesh tray.
Doug
Last edited by dvw; 08/19/19 08:30 PM.
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Re: Oil pressure fluctuation question
[Re: merpar]
#2689484
08/19/19 05:39 PM
08/19/19 05:39 PM
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Joined: Mar 2009
Posts: 2,462 Sydney,Australia
tex013
OP
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OP
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thanks guys . the pan is fully baffled with trapdoors etc . have not noticed this with other factory blocks . I have run this for nearly 10 years . Doug , 8 qts in the sump . The 8-10 psi swing is way down track well after 1/2 track . Street oil pressure , done that with 3 different blocks and 2 different sets of heads , all the same drop at idle from cold to hot . As to a windage tray . I did have one that I tried to get to work with this pan , ended up with more cut away than left . I also would prefer not to use a Accusump , its a crutch . Well I will try an extra quart on Saturday and go from there
Tex
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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Re: Oil pressure fluctuation question
[Re: tex013]
#2689568
08/19/19 09:55 PM
08/19/19 09:55 PM
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Joined: Aug 2003
Posts: 43,157 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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I started making my own crankshaft scrapers around 15 yrs ago out of both steel and aluminum sheet metal(.032 to .063), I build them to fit on the passenger side and shoot for between .030 up to .060 clearances to all the moving parts I do put one hole each right around one inch diameter right by the oil pan rail at each main cap to aid oil drain back I've been told that a good scraper can be worth up to 30 HP above 6000 RPM, the higher the RPM the higher the HP gain
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Oil pressure fluctuation question
[Re: moparx]
#2689713
08/20/19 12:21 PM
08/20/19 12:21 PM
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Joined: Aug 2003
Posts: 43,157 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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No dimpling because I haven't thought of that I use one of the large Unibits and deburr it afterwards I build them so they start at the edge of the timing cover and stop over or at the rear main seal holder, I seal it to the block with a adhesive silicone and cut a oil pan gasket so it meets both ends and cover the rest of the block and glue it down to the block also
Last edited by Cab_Burge; 08/20/19 12:22 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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