Oil pressure fluctuation question - Moparts Forums

Register Log In Moparts Forums Unlawfl's Race & Engine Tech Oil pressure fluctuation question

Print Thread

Oil pressure fluctuation question #2689142 08/18/19 06:24 PM 08/18/19 06:24 PM
Joined: Mar 2009 Posts: 2,457 Sydney,Australia tex013 OP top fuel
tex013 OP top fuel Joined: Mar 2009 Posts: 2,457 Sydney,Australia	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

Re: Oil pressure fluctuation question [Re: tex013] #2689146 08/18/19 06:29 PM 08/18/19 06:29 PM
Joined: Sep 2014 Posts: 4,457 Washington M madscientist master
madscientist master M Joined: Sep 2014 Posts: 4,457 Washington	Originally Posted by tex013 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

Re: Oil pressure fluctuation question [Re: tex013] #2689149 08/18/19 06:46 PM 08/18/19 06:46 PM
Joined: Aug 2003 Posts: 43,097 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,097 Bend,OR USA	Your running out of oil in the sump at those RPM at the end of the run Been there done that with a stock 6 quart Hemi pan in my old pump gas Duster with the 518 C.I. 400 block motor if I let it get low on oil down to the add mark. I had the cam #4 journal grooved to oil the rocker full time, never saw that on others motors that didn't have that mod done to them I ran 5W20 Wt in that motor and I worked on the six pack so it would idle at 850 RPM in gear just to show all the nay sayers that a big roller cam motor can idle at or below 900 RPM in gear with any carb set up That motor had between 18 to 20 Lbs. with oil temps above 180 F at or below 900 RPM I had cut the bypass spring so it had 65 Lbs. above 4500 RPM no matter the oil temps I ended up shifting it at or above 7000 RPM for hundreds of runs with no bad results either Add the extra quart of oil to see if that fixes it or not If it does help either work on improving the oil return or add the Accusump. I have a new 3 quart kit to use on my next fast car with a shallow oil pan Please let us know your results Last edited by Cab_Burge; 08/18/19 07:21 PM. Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Oil pressure fluctuation question [Re: madscientist] #2689156 08/18/19 07:01 PM 08/18/19 07:01 PM
Joined: Jan 2003 Posts: 1,237 North Central, Indiana Roughbird72 pro stock
Roughbird72 pro stock Joined: Jan 2003 Posts: 1,237 North Central, Indiana	Originally Posted by madscientist 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

Re: Oil pressure fluctuation question [Re: Cab_Burge] #2689172 08/18/19 07:50 PM 08/18/19 07:50 PM
Joined: Oct 2007 Posts: 4,205 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,205 New York	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

Re: Oil pressure fluctuation question [Re: tex013] #2689196 08/18/19 08:52 PM 08/18/19 08:52 PM
Joined: Jan 2003 Posts: 30,989 Oregon A AndyF I Win
AndyF I Win A Joined: Jan 2003 Posts: 30,989 Oregon	Add 1/2 a quart to see if that fixes it. If not, add another 1/2 quart. You should find a fill level where it is happy when bracket racing. Why are you running 20/50? Super loose bearing clearances?? I'd use something thinner than that unless the engine builder put it together sloppy and told you to use the thick stuff.

Re: Oil pressure fluctuation question [Re: AndyF] #2689204 08/18/19 09:19 PM 08/18/19 09:19 PM
Joined: Mar 2009 Posts: 2,457 Sydney,Australia tex013 OP top fuel
tex013 OP top fuel Joined: Mar 2009 Posts: 2,457 Sydney,Australia	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

Re: Oil pressure fluctuation question [Re: tex013] #2689231 08/18/19 10:33 PM 08/18/19 10:33 PM
Joined: Aug 2003 Posts: 43,097 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,097 Bend,OR USA	Both of the World iron blocks, one wedge and one hemiroid, had .039 oil restrictor in them to the rocker arms stock Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Oil pressure fluctuation question [Re: tex013] #2689237 08/18/19 10:45 PM 08/18/19 10:45 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	You might be holding to much oil is the top end so try and look at that.. you might look at the oil returns

Re: Oil pressure fluctuation question [Re: MR_P_BODY] #2689277 08/19/19 06:39 AM 08/19/19 06:39 AM
Joined: Mar 2009 Posts: 2,457 Sydney,Australia tex013 OP top fuel
tex013 OP top fuel Joined: Mar 2009 Posts: 2,457 Sydney,Australia	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

Re: Oil pressure fluctuation question [Re: tex013] #2689279 08/19/19 06:48 AM 08/19/19 06:48 AM
Joined: Jan 2005 Posts: 4,243 Charlotte, North Carolina sgcuda master
sgcuda master Joined: Jan 2005 Posts: 4,243 Charlotte, North Carolina	I used to have that problem at the traps using a Moroso deep sump pan. Oil is walking up the front of the block due to the negative g force. Adding a windage tray fixed it.

Re: Oil pressure fluctuation question [Re: sgcuda] #2689294 08/19/19 08:21 AM 08/19/19 08:21 AM
Joined: Mar 2006 Posts: 9,814 MI, usa dvw master
dvw master Joined: Mar 2006 Posts: 9,814 MI, usa	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.

Re: Oil pressure fluctuation question [Re: dvw] #2689311 08/19/19 09:32 AM 08/19/19 09:32 AM
Joined: Oct 2004 Posts: 3,097 back in Georgia dthemi master
dthemi master Joined: Oct 2004 Posts: 3,097 back in Georgia	Since it's starting while you're still under power, I'd say it's most likely windage. Most of the oil getting wrapped up around the crank. We dynoed a motor without a windage tray, then with a basic one, then with a really good pan with full tray, and left and right scrapers. From start to finish 40hp different on 1100hp. Without the tray at 6800 the oil pressure would go 50 to 80 like a hammer and the motor would bellow like it was under changing loads. The basic tray let it run clean, and not wad the oil up, but the last pan was still 15 hp better than the basic tray. I'm not an accusump fan either. Just a crutch for a solvable problem.

Re: Oil pressure fluctuation question [Re: dthemi] #2689321 08/19/19 10:03 AM 08/19/19 10:03 AM
Joined: Jan 2017 Posts: 288 Nevada M merpar enthusiast
merpar enthusiast M Joined: Jan 2017 Posts: 288 Nevada	Poly, is right its an oil pan problem. I would not run it again until pan is fixed. You are starving your bearings of oil. Two things need to be addressed. You need baffles in your pan to trap the oil on exc. and on decel. Then a good windage tray that covers the entire pan top. with louvers for drain back. I've been there and lost a motor because of poor oil pan design. And know other guys who had the same problem. An extra quart of oil won't hurt anything either.

Re: Oil pressure fluctuation question [Re: merpar] #2689484 08/19/19 05:39 PM 08/19/19 05:39 PM
Joined: Mar 2009 Posts: 2,457 Sydney,Australia tex013 OP top fuel
tex013 OP top fuel Joined: Mar 2009 Posts: 2,457 Sydney,Australia	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

Re: Oil pressure fluctuation question [Re: tex013] #2689492 08/19/19 06:09 PM 08/19/19 06:09 PM
Joined: Jul 2004 Posts: 653 Fredericksburg Va P plycuda mopar
plycuda mopar P Joined: Jul 2004 Posts: 653 Fredericksburg Va	I don't know what that world block looks like. but I had the same problem with the indy block. the oil wouldn't drain back fast enough. I hogged out the back and front drain in the lifter valley and it fixed it. I still went and bought a accusump. its nice having 50lbs of oil pressure before you hit the key.

Re: Oil pressure fluctuation question [Re: plycuda] #2689524 08/19/19 07:53 PM 08/19/19 07:53 PM
Joined: Jan 2017 Posts: 288 Nevada M merpar enthusiast
merpar enthusiast M Joined: Jan 2017 Posts: 288 Nevada	windage tray is very important. I have tabs welding just below the top of pan and is held in with fasteners.. Have the entire pan covered except for some louvers on the right side (passenger side). When you shut down the oil will climb up the pan at about a 45 degree angle pulling it away from the pickup. Check with Milodon I believe they have a tray you could modify. Best of luck.

Re: Oil pressure fluctuation question [Re: tex013] #2689568 08/19/19 09:55 PM 08/19/19 09:55 PM
Joined: Aug 2003 Posts: 43,097 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,097 Bend,OR USA	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)

Re: Oil pressure fluctuation question [Re: Cab_Burge] #2689697 08/20/19 11:11 AM 08/20/19 11:11 AM
Joined: Sep 2003 Posts: 19,310 north of coder moparx "Butt Crack Bob"
moparx "Butt Crack Bob" Joined: Sep 2003 Posts: 19,310 north of coder	cab, do you dimple die the drain holes to stiffen the scraper, or isn't it necessary ?

Re: Oil pressure fluctuation question [Re: moparx] #2689713 08/20/19 12:21 PM 08/20/19 12:21 PM
Joined: Aug 2003 Posts: 43,097 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,097 Bend,OR USA	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)

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1