High oil pressure

[DPsuper]

I just installed a melling oil pump on my 1600 turbo motor and my oil pressure goes up to 80psi and when I started it my gauge pegged out past 80psi. Could this be an issue or is high oil pressure ok?

[FJCamper]

Hi DPsuper,

A cast-iron Melling produces some high oil pressure, and seeing first-start cold pressures of 80 PSI is not uncommon. But it should drop fairly fast on warmup. Warm starts should be more like 30- 50 PSI.

120 PSI blows stock coolers.

80 PSI on summer starts might be tolerated, but winter starts are going to be trouble.

What weight oil do you use?

FJC

[Piledriver]

Cast iron pumps have issues at both ends of the temp scale largely due to being iron.
This is ignoring the pump body being undersize ~.003-5" or therabouts to begin with, like most aftermarket pumps for ACVWs.
(Melling pumps are the only iron pumps made for the ACVW I know of)

They can hold great tolerances as the materials used in the pump expand at the same rate...
Unfortunately the engine block is mag or aluminum on an ACVW.

When cold, they can make too much pressure
When hot, the block they SHOULD seal to expands around them, making the air suck and oil leak (internal to case) from poor fit worse.
This causes low hot oil pressure.
Oh, and they drip externally after a while.

Oring-ing the pump body can greatly help the hot pressure issues and the external drip, and the high pressure cold can be dealt with by a Berg-style pressure relief cover and/or "pressure balance grooves" originally used to reduce spark scatter on various engines, but it also neuters the max pressure significantly wihout really hurting the volume.

I'm running a Melling pump now with a dual oringed body and pressure balance grooves, and it actually works quite well.
OTOH it was a science experiment to see what it would take, and if it helped.

Out of the box they are damage waiting to be installed.