Why does oil pressure drop..???

[bobpo]

I know this is normal but I don't understand it. Maybe some of you x-perts can explain this to me.

When I first start and drive Miss Tillie, the Oil Gauge reads about 5+ pounds of pressure. As I continue to drive, the pressure drops to about 3 lbs.

Why is this....?????

[ford1]

as the motor warms up so does the oil, when cold oil is fairly thick, when hot it gets thin, thin oil runs out of the clearances on the mains and crank eadier and faster than thick oil, try pouring stp out of a can when cold, then warm it and try again, you will see what in talking about

[hardtimes]

Originally Posted by bobpo

I know this is normal but I don't understand it. Maybe some of you x-perts can explain this to me.

When I first start and drive Miss Tillie, the Oil Gauge reads about 5+ pounds of pressure. As I continue to drive, the pressure drops to about 3 lbs.

Why is this....?????

Bobpo,
Fairly simple formula, IMO...i.e.- as heat (engine) goes up, viscosity of oil goes down!

[RHD]

I never bother with a oil pressure gauge. What you don't know, won't hurt you.

[Aerocraft]

There is no "cap" on the pump. The oil only has to go a short way, up the pump, turn a corner and quickly gets dumped into the valve chamber. From there it is gravity and splash that delivers the oil. Once the viscosity drops, pressure drops but volumn stays high. Gar Williams

[bobpo]

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Originally Posted by RHD

I never bother with a oil pressure gauge. What you don't know, won't hurt you.

You're probably right. I know it happens, just didn't understand why. THANKS to all of you.

Being from Missouri doesn't help either. (the Show Me State)

[2manycars]

There is no pressure regulator on a model A pump, as it is not intended to create pressure, but volume. The pressure you see is from the friction of the cold thick oil against the passage up the pump body and into the valve chamber, where it dumps out. As the oil heats up, it gets thinner and so can flow easier, and so the lower (or no) pressure reading. An oil guage on a model A only proves the pump is still running, nothing more. The oiling system on a model A is gravity feed to the main bearings and cam bearings, and splash to the rod bearings and pistons. There is no pressure designed into the system.

[V4F]

no pressurization . free flow system .................

[Mike V. Florida]

Originally Posted by bobpo

I know this is normal but I don't understand it. Maybe some of you x-perts can explain this to me.

When I first start and drive Miss Tillie, the Oil Gauge reads about 5+ pounds of pressure. As I continue to drive, the pressure drops to about 3 lbs.

Why is this....?????

Three pounds seems like alot in a normal A.

[Terry, NJ]

My Ford 8N (1952) tractor (4 cyl, flathead) would start at 40 lbs, cold and go zero by the time it was warm. The first time, I went into a panic until a friend told me it was normal. Some "Normal"!
Terry

Originally Posted by bobpo

I know this is normal but I don't understand it. Maybe some of you x-perts can explain this to me.

When I first start and drive Miss Tillie, the Oil Gauge reads about 5+ pounds of pressure. As I continue to drive, the pressure drops to about 3 lbs.

Why is this....?????

[bobpo]

THANKS GUYS, i DON'T KNOW WHY, BUT i FEEL BETTER NOW...AND IT MAKES SENSE....