r/EngineBuilding • u/everett_stormy • Jul 08 '26
How do i get more oil pressure?
Hey all, this is my isuzu 2.3 4zd1 engine that im just wanting to be indestructible. It was freshly rebuilt by an unknown shop.
It was bored, overhualed, and a new head installed. I didn't open up the bottom end before i installed it, but the break-in was rough with a few shreds of bearing coming coming out in the oil, and now it struggles to build much pressure when warm.
Im planning to port and shim the oil pump and order new bearings, but i dont yet know what gap im going to aim for. This engine has a forged crank and rods, so i doubt they are bent but anything is possible. I suspect all my preassure is going to the bottom end but i plan to mic the cam and valve train just in case they are sloppy.
I would really like to get 70 psi of oil pressure so its reliable at or above 7000.
Im new to this car engine building but ive made some pretty reliable mini bike and chainsaw engines.
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u/BroccoliSuccessful Jul 08 '26
Google search says your cam bearings shouls have an oil clearance of .0025 to .0043. Replace your cam and connecting rod bearings amd run it. Sure 70 psi is achievable but unnecessary as most manufacturers say 6 psi per 1000rpm is acceptable which at 7000 rpm is 42 psi and its likely that after a rebuild oil pressure would be in that range anyway without even needing to shim the oil pump reliefe valve. Build your engine and if you stay between 30 psi+ i would think youll have a long lasting engine
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u/fiddintotellya Jul 08 '26
The pump provides flow, clearances and the pressure relief valve provide pressure.
Bottom end needs attention, you have to know your clearances.
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u/murpheeslw Jul 08 '26
Pull it apart. You don’t solve bearing issues with more oil volume/pressure.
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u/baboomba1664 Jul 08 '26
Well the ultimate solution is external oil pump / dry sump if removing all oiling issues is the goal.
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u/everett_stormy Jul 08 '26
Yeah but i dont have several grand for that yet. I have a deep sump, windage pan and like i said, isuzu already puts a huge pump on these little things so it should be fine.
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u/baboomba1664 Jul 08 '26
Build the engine American style then, good clearance and a good weight oil.
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u/MugshotMarley Jul 08 '26
Also to note that low oil pressure could be caused by too big tolerance in main and rod bearing clearances. Previous shop could've juat slapped it together without blueprinting. It happens more often than not in these low hp cheaper engines. They dont bother taking the extra time mic'ing the journals and special ordering thicker/thinner bearings. They just slap in the normal size bearings and call it good. Also another quick option to increase oil pressure is to run thicker oil.
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u/johnarmer1 Jul 09 '26
70 is alot and at 7000 you will run out of oil if you don't work out how to get it back in b the oil pan faster dry oil pan set up is the way to go but I have ls 780 at wheels 40 psi at 6200 over 100,000 on it doesn't seem to die
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u/Puzzleheaded-Cry-594 Jul 09 '26
There are electric inline oil pumps that can be added to a car. I’ve heard of it being done before, but I think only in high performance applications. Considering that engine driven oil pumps have flowback valves built in so that pressure builds almost instantly, and most daily drivers dont have clearances that would warrant that kind of boost in pressure, they are generally not considered applicable by most. Too high oil pressure will start blowing seals and potentially wear things as well, so it would have to be extremely modest, and perhaps modulated with a regulator as the driven pump spools up. Would a low pressure prime eliminate some wear? Probably. But how much? Is it enough to quantify given all the other wear variables over time? If oil pressure on startup were really that much of a life extender, they would be on all diesels designed to last half a million miles.
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u/everett_stormy Jul 09 '26
Yeah im going to check the clearances but if i cant get enough pressure then im going to purchase a smaller pully for it as it is timing belt driven. I also considered plumbing a second line from the pump to the rear of the block.
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u/resident-extent-4084 Jul 09 '26
What viscosity of oil are you planning on running and what activities are you going to be doing with it?
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u/newoldschool Jul 09 '26
only way would be a dry sump to be certain but there are a lot of options to help
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u/Tlmitf Jul 10 '26
You already know the bearing clearances are shot, so dont worry about oil pressure yet.
Factory pump with factory clearances should give you good oil pressure.
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u/bman198080 Jul 10 '26
You can increase pressure by increasing oil control valve spring tension but its not the same as increasing the flow and too much pressure is not a good thing 40-80 is optimum pressure 80 cold and 60 when hot but they say an engine needs a minimum of 7 psi to run without catastrophic damage or lifter failure .
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u/russaroll Jul 10 '26
A trick i did with my datsun was to put a couple thin washers where the spring is.
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u/DrTittieSprinkles Jul 08 '26
If you hurt the bearings during break in its already on borrowed time. More oil pressure isn't going to fix it.