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Old 05-02-2012, 04:25 PM
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low oil pressure on new rebuild

Just had my 390 (1960) totally rebuilt. Before rebuild it had around 20 lbs oil pressure all the time,Now it has 30 when engine is cold then drops down and hoovers between 18 & 22. I have an electric gauge---went & got a manual gauge& it read same thing. There is no engine noise,so I think its getting oil everywhere. Should I be real concerned about this and has anyone else had this happen,and I it is to be concerned about,what has to be done to correct it? Right now it has 30 wt break -in oil in it and will be changing it in about 300 miles. This is not a high revving engine,I have 2.79 rear gears and its in a light car,so when cruising at 50-60 on level it practically idling,but if I do rev it the pressure doesn't go up much
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Gary

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Old 05-02-2012, 04:52 PM
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That sounds pretty low for oil pressure.Did you mic the crank out and did you put in new cam bearings as well? Those are sometimes overlooked.
How do the rocker arms oil? maybe there is a restrictor missing, dont know if there ever was one , or if it suppose to have one, just sayin.Could be.
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Old 05-02-2012, 04:58 PM
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Crank was turned and all new bearings,inc cam bearings
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Old 05-02-2012, 05:12 PM
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Maybe exsessive main bearing clearances new or not

My 390 did the same until i changed the mains, then it carried 80 lbs also did you get a new oil pump?? you can shim the oil pump relief valve with a 3/8ts washer to raise the pressure
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Old 05-02-2012, 05:25 PM
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Put a rebuild kit in oil pump Mains & rods all new
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Old 05-02-2012, 05:27 PM
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Quote:
Originally Posted by rsfyj
My 390 did the same until i changed the mains, then it carried 80 lbs also did you get a new oil pump?? you can shim the oil pump relief valve with a 3/8ts washer to raise the pressure
Do you use just 1 washer,and how much will it help?
hate to think about tearing the pan off already^&*(*&^&
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Old 05-02-2012, 05:50 PM
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Quote:
Originally Posted by yragat
Crank was turned and all new bearings,inc cam bearings

New bearings are good when clearances have been checked and confirmed.
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Old 05-02-2012, 05:58 PM
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usualy one washer will get you 20lbs or so

I had a 390 with a corroded through oil galley in the rear main bearing to the cam area. We drilled it out and put a tube in the bad area. that stopped the leak and the oil pressure cam back. rebuild kits??? hmm// new Melling Oil pump is what you should have.
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Old 05-02-2012, 07:01 PM
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They don't list a new pump for it as far as I know. Block was hot tanked
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Old 05-02-2012, 07:42 PM
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I had

a machine shop clean and re-install an oil pump on my dirt car 351 clevland after a rebuild and the guy left out half of the shims and I only had 30 lbs of oil pressure. I took it apart and shimed it up for 100 lbs. Check out the oil pump its not hard to drop the pan I put main bearings in a 1964 Ford galaxy from the oil pan removed on a lift. about 6hr job. I dropped the oil pan, unbolted the motor mounts jacked up the engine far enough and put spacer blocks in between the engine and mounts, from there i installed all main bearings and a rear rope seal that I soaked over night in oil.
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Old 05-02-2012, 07:58 PM
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do u mean to shim the spring/ if so how much do they normally get shimmed?
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Old 05-03-2012, 05:53 AM
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depends on the pump

and the spring but one washer will raise oil pressure as long as you dont have any internal leaks etc
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Old 05-03-2012, 07:53 AM
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Change the oil

I recently broke in a SBC with 30w Non-detergent, I hope your using Non-d for the break in. I ran about 14-20 PSI at idle on and electric gauge and a mechanical under the hood gauge. Once I change the oil and got rid of the break-in grease and junk the PSI jumped to 38 psi at idle. Try it see what happens....before you start busting gaskets and dripping oil on the floor.
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Old 05-03-2012, 08:18 AM
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Quote:
Originally Posted by Renegade_6
I recently broke in a SBC with 30w Non-detergent, I hope your using Non-d for the break in. I ran about 14-20 PSI at idle on and electric gauge and a mechanical under the hood gauge. Once I change the oil and got rid of the break-in grease and junk the PSI jumped to 38 psi at idle. Try it see what happens....before you start busting gaskets and dripping oil on the floor.
I'm using Brad Penn 30 wt break-in oil and wix filter and ZDDP. ran for 1/2 hr at 1800 rpm to break cam in then drained oil & put in 6 new qts of 30 wt Brad Penn & zddp & new filter and have about 200 miles on that---300 more miles & will change to Brad penn 10W40,or 20W50
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Old 05-03-2012, 08:40 AM
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Change the oil

I went through the same worries. That being said I am a weekend gear head and not a professional engine builder. On my second oil change I ran 20/50 and all my worries disappeared. The oil psi was better with each oil change and after 500 miles.
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