Re: oil pump for hemi with lowish hot oil pressure
[Re: ogopogo]
#2487759
04/25/18 01:18 PM
04/25/18 01:18 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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what psi? (idle & at speed). confirmed with a good mechanical gauge?
live every 24 hour block of time like it's your last day on earth
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Re: oil pump for hemi with lowish hot oil pressure
[Re: ogopogo]
#2487836
04/25/18 04:15 PM
04/25/18 04:15 PM
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Joined: Oct 2007
Posts: 4,206 New York
polyspheric
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master
Joined: Oct 2007
Posts: 4,206
New York
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"High pressure": strong relief spring "High volume": taller gears Other problems: too much oil diverted to valve gear loose bearings
Boffin Emeritus
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Re: oil pump for hemi with lowish hot oil pressure
[Re: ogopogo]
#2487864
04/25/18 05:17 PM
04/25/18 05:17 PM
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Joined: Aug 2003
Posts: 43,176 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,176
Bend,OR USA
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What weight oil was used in it and how much pressure is "low" ? I like and use the old rule of 10 lbs. per 1000 RPM with hot oil, in other words 20 lbs. at 1000 RPM is good as long as it has 65 Lbs. at 6500 RPM ![up up](/ubbthreads/images/graemlins/custom/thumbs_up.gif) I like and use 5W20Wt oil in all my street toys now My old 518 C.I. pump gas wedge stroker motor had 70 lbs. cold at 1200 RPM with 5W20Wt. oil, it had 18 to 20 Lbs. idling at 800 RPM with the oil temps north of 170 F and it had 65 Lbs. max above 3000 RPM with hot oil. I had to trim the high volume bypass spring 1 1/2 coil to get if down that low after running the motor, stock it would have 80 lbs. cold idling and make the bypass spring work above 3000 RPM (it would bypass at 80 Lbs> no matter what the oil temps. where
Last edited by Cab_Burge; 04/25/18 05:18 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: oil pump for hemi with lowish hot oil pressure
[Re: Leigh]
#2487909
04/25/18 07:16 PM
04/25/18 07:16 PM
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Joined: Jul 2006
Posts: 4,179 California
mickm
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master
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California
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My engine is about 5 years since the build, and has about 12 lbs at idle, after being on the highway for a bit. The engine runs cool, 170-190, but after pulling off the highway, will drop down that low. All it needs is a few hundred rpm to be back in the 20+ range, and pressure climbs with RPM to 60-70+ lbs.
After a little city driving, the idle pressure climbs back up to around 20 or so, so it does seem to be an oil temp issue.
I run 20-50, but next time am going to try a straight weight. The bearings are all .005 or so on the loose side. I'd have to look up exactly what they are. I got all the internal components from Tim at FHO, and he said put it together, that's the clearances he wanted to see.
Anyway, it is a little disconcerting. I don't let it sit long at that pressure, if I'm at a light or something I'll rev it every 10-15-20 seconds or so to get the pressure up a bit.
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Re: oil pump for hemi with lowish hot oil pressure
[Re: ogopogo]
#2487930
04/25/18 07:56 PM
04/25/18 07:56 PM
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Joined: May 2004
Posts: 12,388 Taxes & Virus's R-US, NY
Dragula
I Live Here
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I Live Here
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Taxes & Virus's R-US, NY
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I recently aquired a 426 mopar crate hemi that apparantly ran really well/strong,but has lowish oil pressure when hot.it came to me minus oil pump so I am going to order a pump for it today.Should i get stock replacement or hi psi or hi volume pump for it? i plan to run it as is for now... As stated, I would go thru it first and check clearances. Hemi's like putting oil up top in the heads, so if you don't have a big 12quart pan and put a big pump on it, oil pressure will not only get worse, it may lock right up.
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Re: oil pump for hemi with lowish hot oil pressure
[Re: dvw]
#2487993
04/25/18 10:19 PM
04/25/18 10:19 PM
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Joined: Jul 2006
Posts: 4,179 California
mickm
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California
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Straight weight 50 vs 20w50 will do nothing. Its 20w vs 50w cold, not hot. What you have is enough flow paths hot to reduce pressure when the oil is thinner due to temp. So is the oil temp too high? Or is there to much internal leakage? First off I'd be measuring oil temp. Water temp seldom correlates to oil temp. Is the oil temp in range? Then you have a decision. Either your build has excessive leakage in the lifter bores, valve train, drain back issue, etc. Or the engine is in trouble. If you're confident there is no issue, the high volume pump will help. Make sure there is sufficient capacity in the pan. Doug Makes sense, thanks.
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Re: oil pump for hemi with lowish hot oil pressure
[Re: ogopogo]
#2488298
04/26/18 03:16 PM
04/26/18 03:16 PM
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Joined: Jan 2003
Posts: 13,363 Marion, South Carolina [><]
an8sec70cuda
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I Live Here
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Marion, South Carolina [><]
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IMO, get a high volume pump and then manipulate the pressure to your liking w/ the spring. Either trim the spring or shim the cap out w/ an extra gasket or two to drop the pressure.
Dragula...like I've said before, you don't need a 12 quart pan to keep a hemi out of oil starvation. You need to control where the oil you have is going. Your last combo had an issue somewhere that was putting oil somewhere it shouldn't have and starved the vitals. Your big pump and 12 quart pan was a bandaid at best and even that didn't work did it? My 572" hemi has 7.5 quarts in it and survives just fine turning 7500 rpm. Same setup since 2006.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: oil pump for hemi with lowish hot oil pressure
[Re: ogopogo]
#2488312
04/26/18 03:45 PM
04/26/18 03:45 PM
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Joined: Jan 2012
Posts: 2,645 Stuttgart, Arkansas
rickseeman
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Stuttgart, Arkansas
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thanks for the input guys,i know almost nothing about the engine,came from a friend of a friend who said it ran really strong except for that one issue.I likely will pull the pan off and have a quick look before i run it but doubt I will do a full teardown. I have no idea the actual psi #s unfortunately.... I understand you not wanting to do a full teardown. Some people don't want to open that can of worms. The regular Mopar/Melling high volume pump should get you where you want to be. In the old days when I would buy a tired street hemi (these things were always tired) if it didn't have enough oil pressure I would put 50w Valvoline racing oil in it. And if that didn't bring it up I would put a hi volume pump on it. That always solved the problem. These were tired motors with 50,000 miles or 10 years on them. No telling what the clearances were. Good luck.
2011 Drag Pak Challenger
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Re: oil pump for hemi with lowish hot oil pressure
[Re: an8sec70cuda]
#2488485
04/26/18 11:00 PM
04/26/18 11:00 PM
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Joined: May 2004
Posts: 12,388 Taxes & Virus's R-US, NY
Dragula
I Live Here
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I Live Here
Joined: May 2004
Posts: 12,388
Taxes & Virus's R-US, NY
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IMO, get a high volume pump and then manipulate the pressure to your liking w/ the spring. Either trim the spring or shim the cap out w/ an extra gasket or two to drop the pressure.
Dragula...like I've said before, you don't need a 12 quart pan to keep a hemi out of oil starvation. You need to control where the oil you have is going. Your last combo had an issue somewhere that was putting oil somewhere it shouldn't have and starved the vitals. Your big pump and 12 quart pan was a bandaid at best and even that didn't work did it? My 572" hemi has 7.5 quarts in it and survives just fine turning 7500 rpm. Same setup since 2006. Never had a 12 quart pan....gonna have one this time around. Was told by multiple engine builders, my junk was all set to go...We usually see mopars with low idle oil pressure that have excessive crank clearances. We deck the caps and re-line hone. We did this twice on my Hemi...
Last edited by Dragula; 04/26/18 11:03 PM.
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