Thread: oil pressure drop

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Just installed after market oil pressure gauge and sending unit in 70 351 w. In order to install, I had to use bushing and short nippleto install. When I fired it up, pressure went right up to 60 lbs and then settled to 52-53 steady. As soon as I put it in gear. it drops to 20lbs. I realize I need to put a mechanical gauge on it, but why would putting it in gear make it drop/difference?
Any thoughts?

RPM drop.

Don

That much drop? No way that is an acceptable operating pressure, right?

When you raise the rpms slightly (like 100 or 200) does it climb, and if so, what to?

How many miles are on the engine? What weight oil are you running, and is this after it warms up?


Don

Originally Posted by chiefsaj

That much drop? No way that is an acceptable operating pressure, right?

20 lbs. at 800 is not bad. what is it going down the rd. ?

I was a little hesitant to run it too hard, it is a fresh rebuild(5000 miles). When i gave it a little throttle , it did come up into the 30s. Maybe I'm ok if you think that is pretty good.

when I mentione drebuild, just trying to say I didn't think it would be the tolerances.

Originally Posted by chiefsaj

I was a little hesitant to run it too hard, it is a fresh rebuild(5000 miles). When i gave it a little throttle , it did come up into the 30s. Maybe I'm ok if you think that is pretty good.

what Itoldyouso said and its around 40 lbs@2000 rpm's it should be ok.

Thanks guys, I feel better now.

Originally Posted by chiefsaj

Thanks guys, I feel better now.

keep you eye on it and be sure it stays pretty consistent.

Yes, it's electric. There was no resistor supplied, but I used an 18 AWG(oversized) wire to prevent any possible drop.

The gauges had 20AWG and came with a length of 18 to run to the sending unit. When I said over sized, I was comparing it to the gauge wires. Maybe I should run the 14-16...

I don't believe changing the wire size from 14 to 18 gage will make much Dif. in you over all oil pressure. they are not accurate anyway, as long as its consistence.