Oil system myths

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@yellow rose

A couple of questions to get yer opine if I may...

Do you think cavitation affects HV oil pumps?

How does thicker oil behave with an HV pump and related gaskets?

Lastly, any info us big block guys can use? :poke: :D
 
justinp61 said:
In the early 80's I had a 71 RR that I built a 67, 915 headed 440 for. I used a high pressure pump on it and with 6 quarts of oil the gauge would fluctuate. With 7 quarts it was rock solid 72 lbs pressure at cruise, cold it would peg the 100lb gauge. When I rebuilt it I used a HV pump and the pressure was normal with 6 quarts. :realcrazy:
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What weight oil did you use?
 
MarPar said:
@yellow rose

A couple of questions to get yer opine if I may...

Do you think cavitation affects HV oil pumps?

How does thicker oil behave with an HV pump and related gaskets?

Lastly, any info us big block guys can use? :poke: :D
Click to expand...
Cavitation can only occur in any oil pump water pump even up to and including a fire pump on a fire truck if you exceed the supply. If the pump gears or impellers are not damaged. Using a heavier weight oil will certainly use more power to pump.
 
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SGBARRACUDA said:
Cavitation can only occur in in any oil pump water pump even up to and including a fire pump on a fire truck if you exceed the supply. If the pump gears or impellers are not damaged. Using a heavier weight oil will certainly cause more power to pump.
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If you have an HV pump, would it would create more "watts", but not necessarily create more "amps"?

Hence cavitation?

So (in my minds' eye), using a thicker weight oil with an HV pump (versus a standard pump) would create more "amps" by design, no?

Thank you for indulging my curiosity, Roy.

-Mario
 
Not sure about watts and amps. But a HV pump over a standard pump has taller gears and therefore has the capability pump more GPM. Now weather it has the capability to exceed supply or in the case of a engine the supply of oil has been a argument by people since forever.
 
SGBARRACUDA said:
Not sure about watts and amps. But a HV pump over a standard pump has taller gears and therefore has the capability pump more GPM. Now weather it has the capability to exceed supply or in the case of a engine the supply of oil has been a argument by people since forever.
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I’m a bit stumped over the cavitation issue, because I’ve never seen it with a water pump or an oil pump.

I know I’ve heard that cavitation with a water pump is often caused because the suction side of the pump can’t keep up with the output of the pump.

I *think* I’ve seen cavitation on a belt driven fuel pump...but...I was never sure about that, and in the end I felt like the vent was too small but the experts say that it was cavitation and not the vent.

I didn’t have time to sort it out so I opened up the vent AND increased the hose diameter on the suction side of the pump, and it went away.

Which one fixed it? I have no idea.
 
yellow rose said:
I’m a bit stumped over the cavitation issue, because I’ve never seen it with a water pump or an oil pump.

I know I’ve heard that cavitation with a water pump is often caused because the suction side of the pump can’t keep up with the output of the pump.

I *think* I’ve seen cavitation on a belt driven fuel pump...but...I was never sure about that, and in the end I felt like the vent was too small but the experts say that it was cavitation and not the vent.

I didn’t have time to sort it out so I opened up the vent AND increased the hose diameter on the suction side of the pump, and it went away.

Which one fixed it? I have no idea.
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One of the biggest misconceptions when it comes to centrifugal pumps is that water or oil in a engine is “sucked” out of the oil pan or radiator. Which isn’t possible, what actually occurs is the is a pressure drop created by the impeller of a WP or in the case of a oil pump the rotation of the gears creates a lower pressure on the intake side of the pump which causes fluid to travel to a higher pressure. Atmospheric air pressure is 14.7 at sea level. It’s easier to understand it when you stick a straw in your glass of water or soda, when you “suck” on a straw, it travels up the straw because with your mouth you have lower the pressure on the suction side causing the fluid to travel up the straw. Unless your talking about positive displacement pumps which is a different animal.
 
SGBARRACUDA said:
One of the biggest misconceptions when it comes to centrifugal pumps is that water or oil in a engine is “sucked” out of the oil pan or radiator. Which isn’t possible, what actually occurs is the is a pressure drop created by the impeller of a WP or in the case of a oil pump the rotation of the gears creates a lower pressure on the intake side of the pump which causes fluid to travel to a higher pressure. Atmospheric air pressure is 14.7 at sea level. It’s easier to understand it when you stick a straw in your glass of water or soda, when you “suck” on a straw, it travels up the straw because with your mouth you have lower the pressure on the suction side causing the fluid to travel up the straw. Unless your talking about positive displacement pumps which is a different animal.
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So then (because what you said makes 100% perfect sense) the pumps actually function much like a carb. They operate from a pressure differential.

Thanks for that.
 
mbaird said:
Maybe it was factory specific ?
1 plant used gasket .. 1 did not ...?
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I can tell you this........unrelated to the oil pump topic, but Chrysler was one of the few auto makers who did not use exhaust manifold gaskets. A LOT. Their reasoning was two machined surfaces made a good seal. I know oil pumps are not exhaust manifolds, but the principle is the same.
 
@RustyRatRod I though it was for heat transfer from the exhaust manifolds? I ran into a 440 with no exhaust gaskets from a motorhome.
 
pishta said:
@RustyRatRod I though it was for heat transfer from the exhaust manifolds? I ran into a 440 with no exhaust gaskets from a motorhome.
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I don't know and didn't say what the reason was. I just know they didn't do it. I also know two like machined surfaces normally will seal, all else being equal. Up to a point, of course.
 
318willrun said:
my experience:
  • Every factory stock small block mopar I've taken apart did not have a gasket for the oil pump.
  • Every factory stock small block mopar I've taken apart did not have a hole in the bolt for the cam retaining plate.
My 340 had neither but someone was in there before me. I did use the gasket that came with my kit or pump can't remember.
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I don't remember for sure, as it was almost 40 years ago. But I do remember making a oil pump to main cap gasket for a 273 engine, I built. I'm thinking I removed a factory gasket, but there was none in the replacement gasket set.

Edit: I just looked at the 1968 Factory parts manual. It shows a oil pump mounting gasket for the slant six, and the big block. It does not list a gasket for 273,318, or 340 engines
 
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MarPar said:
@yellow rose

A couple of questions to get yer opine if I may...

Do you think cavitation affects HV oil pumps?

How does thicker oil behave with an HV pump and related gaskets?

Lastly, any info us big block guys can use? :poke: :D
Click to expand...

NOT RELATED TO SMALL BLOCKS , BUT A 426 HEMI WOULD PUMP THE PAN DRY AT DRAGRACING REVS !
And both of the ones I had came from the factory with a gasket between the pump and block , just like my 440 did------------
 
The first small block I ever helped build was a late 70s 360, and during assembly (I was about 14), I asked why there was no gasket between the pump and rear main cap. Dad told me he had never seen one (mind you he worked in a Dodge dealership in the early 80s through the 2000s) and swore that Chrysler never used one from the factory on small blocks. Is that true? Who knows, but it's interesting to me why they might use one on engine A and not on engine B. Maybe they were there in engines that the mating surface(s) weren't machined correctly?
 
I have built with and without a gasket with no problems either way. If I have one I use it, if I don't then I don't.

Look at the other side of the pump. That 5 bolt plate on the bottom of the oil pump has no gasket....
 
The issue of direct oiling to timing chains may have more to do with modern engines than our classics. Engines now often last several hundred thousand miles, and their computer controlled fuel and ignition requiring more precise cam timing. Timing chain wear has become an issue in ways that weren't considered in the days of carburetors and points ignition.
The new oil requirements introduced in 2020 of API SP and ILSAC GF-6 mandate increased protection against timing chain wear. So, it's certainly a modern engine issue.
 
Mopar Sam said:
I have built with and without a gasket with no problems either way. If I have one I use it, if I don't then I don't.

Look at the other side of the pump. That 5 bolt plate on the bottom of the oil pump has no gasket....
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If I'm installing the original oil pump and it came with no gasket, then I don't use a gasket either. If it worked for the XXXXXX miles without one, then the machining surfaces must not be leaking and i like the idea of no gasket to blow out. If I'm installing a different/new pump, then i use the gasket for sure.... with Indian head shellac :)
 
318willrun said:
my experience:
  • Every factory stock small block mopar I've taken apart did not have a gasket for the oil pump.
  • Every factory stock small block mopar I've taken apart did not have a hole in the bolt for the cam retaining plate.
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  • From what I remember, early, 64-? small block engines used a gasket between the oil pump and the main cap. Some where along the time line they stopped using the gasket and it went AWOL from full gasket sets and replacement oil pumps.

  • The only original engines I have seen to have the cam thrust plate bolt with the through hole were 70-73 340's and the early HP 360's to about 1976 using the double roller chain. No oil gallery plugs. I never had a virgin 68 or 69 340. I was never interested in later 318's or 360's, so I have no experience with them. Early 273's and 318's were 4 solid bolts, silent chain, and a cast cam gear. Later 318's and 360's used 3 bolts, a sheet metal tab to oil the silent chain using a plastic coated aluminum cam gear.
 
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