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mark5775

Low oil pressure after overhaul.

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I will try to be brief but have a lot to cover. Just overhauled 656G. Polished crank, new main and rod bearings. New piston and sleeves. Oil lite blinking at low idle. Put gauge on it and found to  be around 6 pounds. Order and installed new oil regulating poppet and spring. Still low. Ordered and installed new oil pump. At 1600 rpm pressure is 20 lbs and drops as it gets warmed up. Using IH SAE 30 oil. I am stumped. Took pan back off and plastic gauged one rod and one main. Both checked out  good. Runs about 6 lbs at idle. Ran with valve cover off and drip seems normal. HELP

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camshaft bearings worn maybe

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21 minutes ago, Wes806 said:

camshaft bearings worn maybe

Sounds about right.

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I know I have been guilty of not putting new camshaft bearings in on some overhauls. Been lucky though that it didn't  hurt oil pressure do know that they will affect it.

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Mark

         Are you sure that the oil galley plugs are all installed?      Are you sure that the oil pump pickup screen and suction tube are clean and open?    I have had to put an oil supply in a can and hang the can under the oil suction screen.   Then run the engine with the oil pan off.   Check quickly where the oil is pouring out.   It is very messy but you will know where the oil is coming out.

GT&T

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Start with the easy stuff did it have better oil pressure before the overhaul? If your engine came with an aluminum filter base that had phonelic valves to control oil pressure, filter bypass, and drain back the seat in the casting gave us trouble when you ordered new poppets you got metal ones but it was a hit or miss if that would help if the seat was bad you either had to figure out how to get it remachined or replace the casting. Do you have the correct gasket between the base and the block? most overhaul kits have 4 gaskets, two look close to correct, the gasket must match the base or you can loose pressure there I have seen that before. 

 

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3 hours ago, R190 said:

Start with the easy stuff did it have better oil pressure before the overhaul? If your engine came with an aluminum filter base that had phonelic valves to control oil pressure, filter bypass, and drain back the seat in the casting gave us trouble when you ordered new poppets you got metal ones but it was a hit or miss if that would help if the seat was bad you either had to figure out how to get it remachined or replace the casting. Do you have the correct gasket between the base and the block? most overhaul kits have 4 gaskets, two look close to correct, the gasket must match the base or you can loose pressure there I have seen that before. 

 

Had the same thing on a 291 once. Had good pressure a few days then dropped off. Put in a new oil pump and no difference. Found a piece of gasket in one of the valves in the filter base. Cleaned it out and been running good ever since.

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had same thing happen few tears ago. found a piece of crap under one of the valves behind the filter base. did you have the filter base off ????  if you did I would still double check, just like the above posts say.

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Did you rebuild the pump. Or a new one . 

I find the Farmall c I have are all worn out 

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18 hours ago, Wes806 said:

camshaft bearings worn maybe

Sorry, didn't mention that the cam bearings were replaced. This was done at a machine shop because he cooked the block out.  Prior to overhaul the pressure was not great because the oil light would flicker on a low idle. (Didn't know what the pressure was because only installed mechanical gauge after overhaul) . Engine was very tired, thus the reason for overhaul. Double checked the oil filter mounting gasket and sure that is correct. The seat on the oil pressure regulating poppet (steel poppet removed and replaced with new) has a nick on the inside 1/2 that does not extend to the outside so don't feel that is problem.  Can't believe I am loosing 35 to 40 lbs of pressure thru that.  I can remove again and post picture is someone thinks that is a possibility. Thanks to all who replied.  

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I had a machine shop once install the second or third from the back cam bearing wrong on a 291 and it would act the same as yours. It took a while to find that one.

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Ok, Pulled pan and plumbed a weed sprayer full of oil into the oil pressure sending port. Pumped it up and oil pours out around the back cam bearing? Is this the normal place for excess oil to dump? It pours out before building any pressure.

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That is where your problem is. It is going to have to go back to the machine shop so they can fix their error.

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Mark

        You have done a fine job of diagnosing the problem, congratulations.   It is a shame that you will have to tear the engine back down,  but now you know what is wrong.   I feel your pain.

GT&T

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