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how much oil pressure is too much?

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how much oil pressure is too much?

Postby ap72 » Fri Nov 15, 2013 9:21 am

I'm looking at various high pressure springs for the standard sbc oil pump and I'm curious as to how high is too high? I know higher pressure means more parasitic loss but I'd rather trade that for dependability.

I see they have a 90lb spring... dare I venture that high?
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Re: how much oil pressure is too much?

Postby rickseeman » Fri Nov 15, 2013 9:26 am

Why would you?
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Re: how much oil pressure is too much?

Postby perfconn » Fri Nov 15, 2013 9:35 am

Volume is what cools the bearings not pressure
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Re: how much oil pressure is too much?

Postby governor » Fri Nov 15, 2013 9:39 am

What block? if it is a block with priority oiling mains much less is needed. Also your bearing clearance has to enter in, so no cut and dried question. 90lb hell no!

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Re: how much oil pressure is too much?

Postby ap72 » Fri Nov 15, 2013 9:41 am

and more pressure means more volume, right?

standard block, LT1 actually.
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Re: how much oil pressure is too much?

Postby ap72 » Fri Nov 15, 2013 9:42 am

I need to check the clearances this weekend.

If 90lb is a hell no, what is the max?
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Re: how much oil pressure is too much?

Postby governor » Fri Nov 15, 2013 9:47 am

What block? what oil pan. 65lb hot is plenty, in my SHP block motors I run 45-50lb hot with HV not HP pumps.

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Re: how much oil pressure is too much?

Postby engineguyBill » Fri Nov 15, 2013 9:54 am

If you are looking for dependability, then go with a high volume oil pump and shoot for maximum pressure around 50# in a warmed up engine. Excessive pressure is not necessary and no, higher pressure does not result in more volume.
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Re: how much oil pressure is too much?

Postby ap72 » Fri Nov 15, 2013 10:07 am

already have a HV pump with a larger pickup and a ported inlet and rear main cap. I was just looking to get all I can out of the oiling system.

On the same note, 1/2 groove or 3/4 groove main bearings?
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Re: how much oil pressure is too much?

Postby Kevin Johnson » Fri Nov 15, 2013 10:08 am

Higher pressure will allow a greater volume of entrained air to enter solution IF the air bubbles are of sufficiently small size. Greater cooling ability with flow subsumes ideal fluids, not highly aerated ones. That being said, if you have a situation where there is a lot of aeration then that points to a separate set of problems that should be addressed particularly if reliability is your goal.
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Re: how much oil pressure is too much?

Postby swatson454 » Fri Nov 15, 2013 10:09 am

Here's a thought:

If a high-volume pump is installed that's capable of gobs of pressure but it's regulated by a 50 or 60 pound spring, isn't it simply bypassing that extra volume? If that's the case, wouldn't a standard-volume pump with the same spring make more sense?


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Re: how much oil pressure is too much?

Postby engineguyBill » Fri Nov 15, 2013 10:10 am

1/2 groove main bearings.
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Re: how much oil pressure is too much?

Postby ap72 » Fri Nov 15, 2013 10:14 am

swatson454 wrote:Here's a thought:

If a high-volume pump is installed that's capable of gobs of pressure but it's regulated by a 50 or 60 pound spring, isn't it simply bypassing that extra volume? If that's the case, wouldn't a standard-volume pump with the same spring make more sense?


Shawn


HV pumps move more oil below the pressure relief point- lower rpm. at rpm then yes the std volume pump will flow the same.

That much I know, but I'm a water hydraulics guy, not an engine bearing durability guy.
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Re: how much oil pressure is too much?

Postby Fordracer347 » Fri Nov 15, 2013 10:15 am

If you are still concerned, the old rule of thumb of 10 psi for every 1000 RPM has been a hot rod standard for decades and it has worked great. Many have found that with better control they can run far less than that and be just fine.

I prefer to use the 180* oil groove mains over the 270*, expecially on a conventional SBC there is no need for the added groove it can be more detrimental than beneficial. Some of the cup stuff was even using cap side bearings and cutting what groove they needed into them so they had more bearing surface area. That might have all changed since last I had heard but you get the idea.
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Re: how much oil pressure is too much?

Postby nhrastocker » Fri Nov 15, 2013 10:30 am

Fordracer347 wrote:If you are still concerned, the old rule of thumb of 10 psi for every 1000 RPM has been a hot rod standard for decades and it has worked great. Many have found that with better control they can run far less than that and be just fine.


That rule is old school.
My premise is to consider engine torque over RPM. This means 10 psi for every 100ft/lbs of torque.

If I was to use the RPM based rule of thumb, I would have to run over 100 psi on a 10500 RPM Comp Eliminator engine!
With engines that turn 9700 RPM+, I have always set the pressure around 55~60 psi and never had a single issue.
Again, you have to consider the type of bearing, clearances and the oil pan design.
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