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Eric Hodges
Samba Member
Joined: May 01, 2011
Posts: 95
Location: Simi
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 Posted: Sat May 10, 2025 10:10 am Post subject: High Oil Pressure |
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Hi experts.
I have a sky-high oil pressure problem. Up to about 3000 rpm, the pressure is normal, 45 pounds. Above that rpm, the pressure climbs to peg the gauge at 80 pounds.
I've removed the two oil pistons and blown compressed air through the gallery. No change.
I've removed the piston at the flywheel and run it.
No change.
I've stuck a wire up the flywheel gallery supply line, but it couldn't make the turn.
I believe there's a plug in the oil gallery somewhere, and I'm hesitant to take the world apart to gain access to all the gallerys.
Any Ideas?
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'74 Super, worn, becoming DD |
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DerrickfromNC1
Samba Member
Joined: October 24, 2008
Posts: 1394
Location: North Carolina
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| Posted: Sat May 10, 2025 10:46 am Post subject: Re: High Oil Pressure |
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| What kind of oil pressure guage & sending unit. I think VDO has 2 different sending units with a different range(0-80 & 0-150psi) and must go with the matching guage. I would test actual pressure with a mechanical guage at the sending unit port. |
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 42037
Location: at the beach
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| Posted: Sat May 10, 2025 10:52 am Post subject: Re: High Oil Pressure |
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| DerrickfromNC1 wrote: |
| What kind of oil pressure guage & sending unit. I think VDO has 2 different sending units with a different range(0-80 & 0-150psi) and must go with the matching gauge. I would test actual pressure with a mechanical gauge at the sending unit port. |
what Derrick said ^^^
Also, you need 10 PSI per 1000 RPM. I manage my oil pressure to about 12 - 14 psi per 1000 when the oil is at max temp, by choosing a viscosity that allows that.
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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Eric Hodges
Samba Member
Joined: May 01, 2011
Posts: 95
Location: Simi
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| Posted: Sat May 10, 2025 11:34 am Post subject: Re: High Oil Pressure |
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The oil pressure was fine at all rpm's, until I took the engine out to find a vacuum leak at the intake manifold boot.
Then the problem. I bought the 80 psi gauge and sender at the same time
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'74 Super, worn, becoming DD |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42037
Location: at the beach
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| Posted: Sat May 10, 2025 12:45 pm Post subject: Re: High Oil Pressure |
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| Eric Hodges wrote: |
The oil pressure was fine at all rpm's, until I took the engine out to find a vacuum leak at the intake manifold boot.
Then the problem. I bought the 80 psi gauge and sender at the same time |
Have you cross checked the sender number to the gauge to be sure they sent you the correct one? Have you tried the old gauge from when the engine worked fine? I guess you had a gauge before to be able to make the statement that it worked fine before. Does the new gauge have settings that are configurable if it is not an older style VDO gauge?
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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Eric Hodges
Samba Member
Joined: May 01, 2011
Posts: 95
Location: Simi
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| Posted: Sat May 10, 2025 5:56 pm Post subject: Re: High Oil Pressure |
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The gauge and the sender are old.
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'74 Super, worn, becoming DD |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42037
Location: at the beach
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| Posted: Sat May 10, 2025 6:06 pm Post subject: Re: High Oil Pressure |
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| Eric Hodges wrote: |
| The gauge and the sender are old. |
what is the gauge model number and the sender number?
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin |
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modok
Samba Member
Joined: October 30, 2009
Posts: 27560
Location: Colorado Springs
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| Posted: Sat May 10, 2025 6:09 pm Post subject: Re: High Oil Pressure |
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| Eric Hodges wrote: |
Hi experts.
I've removed the piston at the flywheel and run it.
No change.
I |
Hold on, do you mean you removed the plunger and spring and put the threaded plug back and ran the engine
OR
you left the threaded plug out and ran the engine with the thing just open?
huh, well, no, that would let all the oil drain out right?
Need clarity on this. 
The oil relief bore should have two holes drilled sideways through it in the bore.
one near the top which is where the oil passes back into the sump when the plunger gets pushed down, and the other below the plunger which is a vent.
Both those holes need to be there for it to work. |
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modok
Samba Member
Joined: October 30, 2009
Posts: 27560
Location: Colorado Springs
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| Posted: Sat May 10, 2025 6:16 pm Post subject: Re: High Oil Pressure |
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Tho it's not a great angle, in this cutaway pic you can see the two holes drilled horizontally through the flywheel side oil plunger bore.
the upper hole exits into the case between the lifter and the pushrod tube.
the lower hole goes into the inside of the sump about at the oil level
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Eric Hodges
Samba Member
Joined: May 01, 2011
Posts: 95
Location: Simi
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| Posted: Sun May 11, 2025 5:11 am Post subject: Re: High Oil Pressure |
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Just to clarify.
The oil pump/sender was purchased in 2016-ish and not changed, not removed not replaced.
The oil pressure regulates properly from about 1500 to 3000. It rises to 45 psi and stays to about 3000 rpm. Then, as the rpm rises, the oil pressure rises to 80 psi, pegging the gauge.
I removed the piston and spring from the forward (flywheel) plunger and replaced the threaded plug. No leaks.
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'74 Super, worn, becoming DD |
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Eric Hodges
Samba Member
Joined: May 01, 2011
Posts: 95
Location: Simi
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| Posted: Sun May 11, 2025 5:19 am Post subject: Re: High Oil Pressure |
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My guess is a plugged gallery somewhere, and I don't relish the thought of tearing it apart and sending the cases out for a hot tank....
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esde
Samba Member
Joined: October 20, 2007
Posts: 6289
Location: central rust belt
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| Posted: Sun May 11, 2025 6:59 am Post subject: Re: High Oil Pressure |
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| Eric Hodges wrote: |
Just to clarify.
I removed the piston and spring from the forward (flywheel) plunger and replaced the threaded plug. No leaks. |
Do you mean, that you removed the piston and spring completely, and put the plug back with no piston/ spring?
If not, what exactly did you do?
It sounds like, the issue is with that spring and piston, as it should open to dump the high pressure you are seeing. I would look for another OEM spring and piston, and make sure the piston edges are eased, and check that it moves freely in the bore.
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modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that. |
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anthax
Samba Member
Joined: October 21, 2016
Posts: 306
Location: Hälsingland, Sweden
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| Posted: Sun May 11, 2025 9:48 am Post subject: Re: High Oil Pressure |
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| What size of oil pump? 30mm? |
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Eric Hodges
Samba Member
Joined: May 01, 2011
Posts: 95
Location: Simi
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| Posted: Sun May 11, 2025 6:16 pm Post subject: Re: High Oil Pressure |
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I found the problem.
My apologies for sending you all out on my wild goose chase,
Sudden problems tend to point to the last thing you did, which in my case was R and R the engine. Everything was disconnected and reconnected. The thumb nut on the sender, that goes to the gauge, was loose.
I tightened it and I now have 40 psi no matter what the rpm.
Fixed.
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'74 Super, worn, becoming DD |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23002
Location: Oklahoma City
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| Posted: Sun May 11, 2025 9:55 pm Post subject: Re: High Oil Pressure |
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| Eric Hodges wrote: |
I found the problem.
My apologies for sending you all out on my wild goose chase,
Sudden problems tend to point to the last thing you did, which in my case was R and R the engine. Everything was disconnected and reconnected. The thumb nut on the sender, that goes to the gauge, was loose.
I tightened it and I now have 40 psi no matter what the rpm.
Fixed. |
So....at 850 rpm idle you have 40 psi....and like....at 4500 rpm you have 40 psi?
Not quite so sure that is an improvement.
Ray |
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