Ih 350 utility low oil pressure

Not to old of a engine rebuild. I'm just not happy with oil pressure. starts out with about 40 and drops to 20 after warm up. do you guys think that replacing pressure relief valve and relief valve spring in the oil pump will help? Any thoughts would be appreciated.

What weight oil are you running?

What was done on rebuild, cam bearings ? Main bearings? Rod bearings?

30 this summer

Done it all

What are u calling rebuild? From bare block with all brgs. replaced? Have u installed a master gauge and got some real numbers? Readings at idle cold and hot , same at wot camshaft brgs. play a big roll in pressure drop after hot

bare block. all bearings, it was a rebuild kit but I don't remember cam bearings maybe .I even replaced the sleeves,

Before you do anything else check oil pressure with a known good (master) gage. I had a sudden "low oil pressure" issue (20 psi when warmed up dropping to near 0 at idle) on a Super M . Turned out the oil gage was outta whack and was reading 40 psi below actual. A replacement gage solved the problem.

Not likely your oil pump relief valve is the issue. If it were pressure would stay constantly low even when cold. More likely it is from worn cam bearings. Or possibly the oil pump cover plate is scored and needs resurfacing, or the cover gasket has blown out.

Were it my tractor, and if the pressure holds steady at 20 (or even 10) psi hot I'd simply run it as is. And perhaps switch to 15W-40 oil which may boost pressure a bit. (We have a Super H that runs 25 psi at speed and 10 at idle using 15-W40. Been this way at least 20 years - it continues to run fine....)

20 psi is fine.

Ok so you did all that , BUT did you have the crank checked , did you plasta gauge the rods and mains you don't remember replacing cam bearings nor rebuilding or replacing the oil pump . That's not a rebuild you threw parts at it and expected it to be all better. Probably running 10W 30 oil .

hummm.

Simple things first. Use a known good oil pressure gauge to test. If same readings, did you do anything to the oil filter. You know it has a bypass style filtering system with an orifice in the bolt to regulate flow through filter.

Any increase in size of that orifice will change pressure drastically. Some after market add on kits are made wrong so be sure that hole is correct. I don't know the size but you could easily compare it to any H, M , 300, 400 etc . Even just temporarily block the hole for a test. Oil goes to all other parts like normal with that hole blocked.

Then the oil pump. With that low of pressure when start up you could have broken spring or I have seen some tractors with the wrong piston put in oil pump. It should be straight full length of piston and no reduced size near lower end. One of the first M Farmalls I worked on I found that wrong valve. I believe it is for a diesel as they run much less oil pressure.

Now, oil pump. Pretty rare for a bad cover on a 300 as they are thick and don't warp. BUT, very common for the shaft in pump to wear badly so gear moves away from side of housing.

I replaced a lot of cam bushings in H and M's but never really saw any terribly worn. Saw them turn in block and move out of place because they were too tight when installed.

Also, some times oil gallery plug gets left out in front of engine under cover. Especially when block is soaked to completely clean it.

Pressure should run near 70 psi on that engine, warmed up, moderate to high rpm's. Will it work with lower pressure, of course, but something is not right.

Ok so its been a few years back but I did take the block, crank, and cam to a motor guy at napa and he and I looked at them and he said they looked fine. No scores or gouges. We didn't gauge the crank or cam. I know I replaced main and rod bearings, rings, seals, etc., napa also went over the head etc. I still can't remember about the cam bearings if they were with the kit. I had napa to reseal and replace sleeves due to coolant leaking into oil. I did nothing to oil pump just reinstall. The reason for tear down was because of the coolant leak into oil. Didn't know oil pressure at that time due to no gauge bought this tractor at a auction.it ran decent before tear down.

Also running 30 weight low ash from case ih

So I don't remember removing the oil gallery plug. does it screw in? The block was cleaned. Will that have affect on oil pressure?

Agreed. 20 PSI is pretty good pressure for operating.

It’s same as a frost plug. Yes have effect as your loosing oil along the path. When u have a spray nozzle on a garden hose you have pressure in the hose when spraying , open the nozzle or take it off and no pressure .
Same with worn brgs. You are loosing more oil and even more when oil get hot , and pump can’t keep the pressure up.

nothing wrong with 20lbs oil pressure

I don't know but i'd switch to a 15w40 and see what it does.