Oil presure

mikeintn

Member
My 1948 ZTN oil pressure goes down as the RPM goes up, never seen this before, every engine I've been around always works the opposite, at idle its at 25 psi, and will go down to 15 psi at full throttle, hot or cold, runs great, changed oil when I got it before starting it, just wondering if anyone has seen this before, or what causes it, or normal for MM? Thanks Mike
 
My first guess is the sump screen is almost plugged tight and when you rev it up the pump is being starved for oil.
MMDEL
 
I remember my dad talking about years ago when some people would change oil in the R-Z motors, if it was thick and wouldn't come out they would stick a screw driver up through the drain hole, which of course would go right through the oil sump screen. I have run across some that way.
 
That's a good idea, but I forgot to say I took the side cover off the engine and checked it when I changed the oil, it wasn't bad but I did clean it and the bottom of the crank case out, I know it sounds weird, but the oil pressure goes down as RPM goes up.
 
Ive never been within fifty feet of a ZTN but it sure sounds like either a restriction possibly in the pickup tube/pump or the strangest pressure relief valve problem in history.
 
Sounds like we are starting to grasp at straws. It might be that the woodruff key is sheared on the oil pump shaft, but is fitting tight, and will carry the load till the shaft speeds up. Far fetched maybe. In any event the pump area and relief valve will need to be checked. First remove the pipe plugs on the front side of the pump, and check passageways.
MMDEL
 
Its got a few in front of it before it gets finished, may take oil pump out and look at it when I get back on it. Thanks
 
i would check the pressure with a master gauge,if you have not done so, to eliminate any gauge problem. worn brgs would cause the oil pres. to drop once warmed up. sure acts like something in the pump pickup.
 

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