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How Much Oil Pressure Before Starting New Engine

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#1 AndrewT


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Posted 27 November 2020 - 12:53 PM

I've done lots of searches and the advice is a bit conflicting.

My engine is completely rebuilt including a new oil pump.  I've got the plugs out and it's spinning freely on the starter motor.  The oil light is out but I'm only getting 25-35 psi on the pressure gauge.

Other posts suggest 50+ psi before starting but I just can't get it that high on the starter motor. If idling at say 1,000 rpm gives pressure of 60 psi when cold and 20 psi when hot then the much slower speed of the starter motor would struggle to get to 60psi wouldn't it?

Would 30ish psi therefore be safe to start? It's a brand new electric gauge and matched sender plumbed in to a sandwich plate on the filter so I can only assume that it's correctly calibrated.

It seems ok, nothing is leaking and once running I'll keep a close eye to make sure pressure does go up properly but obviously don't want to start it if this is too low.

#2 goudoogje


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Posted 27 November 2020 - 01:06 PM

I had this once, and on my case the oil pressure spring was the wrong one, i replaced it from a another engine, and i did had some more pressure. Can't remember the numbers of course, but mabye something to check? 

#3 whistler


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Posted 27 November 2020 - 02:23 PM

I usually achieve about 55 to 60psi on starter on a rebuild. Agree about the relief valve.

#4 Dusky


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Posted 27 November 2020 - 02:27 PM

You only need that oil pressure to make sure all galleries are filled with oil. The less spinning on the starter the better for the camshaft. Fire 'r up!

#5 Spider


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Posted 27 November 2020 - 05:02 PM

There's clearly Oil Flowing there, I'd fire it up at that and see where the OP goes then.

Like Dusky says, too much cranking on a fresh engine isn't a good idea.

#6 AndrewT


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Posted 27 November 2020 - 06:01 PM

Fair enough. I'll fire it up tomorrow morning and hope that nothing explodey occurs.

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