Low oil pressure when hot

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mod5v

mod5v

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New build lots of used parts. 360+.030, J heads. fresh turned crank full grove main bearings. opened up oil passages.. solid cam .365 intake lobe .373 ex lobe using the old 273 type lifters{dumb bell shape}. so when its cold with 30w breakin oil I get 50psi at idle but as soon as it warms up to 200 deg I'm down to 10-15 psi. I am wondering if with this much lift in the cam if the lifters are letting the oil bleed by and that's why the pressure drops so bad when oil is warm.
 
dumb bell solid lifter.... Is that a answer or just having fun?
 
If the 'waistbands' above the lifter bore is the issue, you ought to be able to spot it peeking above the tops of one or more bores as you rotate the engine around with the intake manifold off. A 50 to 15 psi drop at a low idle stone cold to really hot is not out of line ....but that could vary with your clearances, etc. What pressure do you get revved and cold/cool, vs 200F?
 
lets not forget that you are running an engine which is set up as a "large pressure leak" with the full groove bearings and the oiling mods you did

now, I know, this should effect cold oil pressure as well, but it may explain the larger then expected drop in cold-hot pressure
 
the open center part of the lifter expose the oil galleries..and you lose oil pressure...
 
Exactly. Since the lifters do not have full bodies, they expose the oil galleries just like Tony said. I assume you are running a high volume pump?
 
Thank You 70aar that was my thought but I just wanted someone with more experience to confirm it. also yes I have a HV pump and also a 10 qt pan and have opened up the drain back holes from the heads and lifter valley so I'm not pumping pan dry. Cold pressures are 50 idle 1200rpm to 75 at 4000. hot are 10psi idle and 40 at 4k. I will pull the intake and see how close the "waistband" is to being exposed at full lift and try to calculate where its at on the base. but I will get some solid bore lifters just to be safe.
 
It's not anything to do with full groove main bearings.
I haven't heard of anyone using the dumbbell lifters in years.
 
I used full grooved main bearings in my last build and it definitely had an affect on oil pressure. However 10-15 at idle hot with 30w doesn't worry me. I'd switch to a 40 or 50w and call it a day if you want a touch more pressure on your gauge. I run 0w40 in mine.
 
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That is what I thought. Why would anyone use these in a SB Mopar? I have only heard bad things when they do?
 
mod5v said:
hot are 10psi idle and 40 at 4k
Click to expand...

40 PSI at 4k that sounds low to me, does the pressure go up the higher you rev it past that? My understanding of Mopar oil pumps the pressure/flow jumps up rapidly when the engine is revved (unlike Chebbies that slowly build pressure consistent with RPM); it should be giving you max pressure at lower RPMs and leveling off as the revs climb. My $0.02

EDIT: Yup those lifters look like they'd cause a big time pressure loss, the oiling passages in the lifter bores are meant to be covered up fully by the lifter body, I bet you will see oil gushing out the lifter bores if you prime the oil pump with the intake off.
 
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P= F/A

Pressure equals Force over Area.

By opening up the oiling passages and using the dumbbell lifters. You have increased the area. Decreasing the pressure. Adding heavier oil will increase the force, increasing the pressure. Personally I prefer pressure over flow. Pressure = oil gets everywhere it needs to. Flow = oil gets back to pan quicker. I much prefer oil getting everywhere it needs to over how fast it gets back to the pan. Running heavier oil is sort of a bandaid. I would change your lifters and see what kind of change you get in pressure.

My 340 has 70-80 cold idle psi. 40 hot idle psi in park, 30 in gear. Gains 10 psi per 1k rpm to about 60 psi. Never worried about oil pressure once in my setup.
 
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