New Motor Start up with Xtremely High oil pressure

[Dadandson]

Turned the key on the new motor tonight. Fired right up and runs like a top. No smoke, 2,000 rpm's for twenty minutes, everything went well. One issue; The idle oil pressure is 60 and it buries the gauge to 100 when rmp's increase. This does not sound right. Will the oil pressure come down after time or is there something else going on?

 

[Deleted member 8987]

That's inverse of most folks.....but, no.
Shouldn't be that high.

However:
What is it really?

Have you screwed a mechanical gauge into the port?

I think I would do that first.

Otherwise, the relief valve should take over long before 100, so that's next.

 

[Dadandson]

I was thinking relief valve. I will disassemble and inspect tonight. Does the numbers on the gage correlate to pounds as a mechanical gauge would i.e. 60 on the car gauge equals 60 on the mechanical gauge?

 

[Deleted member 8987]

Should.

I don't think a 1974 still used Whitworth Gauge Grading.

(that's a joke).

Before you tear it down, I would confirm pressure.

You will be nice and high on a new engine, with fresh oil, but the relief valve should dump it at a pre-set level.

BTW, many decades of experience.....I have no idea what oil you have in it, but I would never use heavy oil for break-in.
You need something lightweight to get into tight spots.

In fact, I used to use 20WT non-detergent in my engines, until it became difficult to find, run it for 500-1000 and drop it (hot) and the filter.

 

[hpmowog]

Check for a stuck relief valve first. I've had a galled relief valve stick in the bore before and have the same symptoms.

 

[Deleted member 8987]

Reason I said check the actual pressure first, is A) it's easy, B) the sender was out, and may have been dropped, and C) I have certainly seen LBC gauges that were far from correct.

For all anybody knows, it was reading high before the rebuild with horrible tolerances, hence "looked" normal.

Second is relief valve, as Lord Knows we've seen that happen.

But, until you have empirical data to support going further, I always want to know what it actually IS.

To wit: I have a couple of gauges for oil on my Jag, one was reading very low.....checked pressure mechanically, it was fine.
Sender replaced (leaking anyway), no change. Swapped the dash gauge, it now reads close to mechanical, and I am happy.

In another marque, I have boxes of oil senders and water temp senders, usually match them to a gauge by A) mechanical oil test and B) thermostat in tank.

They are not all necessarily "bad", just have variations that I match to the variation in the dash gauges.

In a shop, you immediately go for the relief valve instead of actually reading the pressure, you'd probably get fired.

You would then have no idea what it actually was before you changed out the relief valve.