oil pressure drops at high speed

Kurt Combs · Post by **Kurt Combs** » Wed Oct 15, 2008 11:28 am

My oil pressure drops at high speed, for me that means 65 mph+. I am running stock Ford gauges in a 1972 F250 with a 360. Engine is old and tired with bandaid repairs like; new rod bearings, timing chain, junkyard heads, and it has a little valve noise, probably a tired lifter. Uses a little oil, like a quart every 400-500 miles. What has me stumped is that my oil pressure is better at 55-60 mph, than it is at 65-70 mph. If I slow down for a few miles the oil pressure goes back up. I am running 15-40 Delo oil and I change it frequently (or it changes itself). I am not worried about the pressure drop, just curious. (BTW, I have a 390 rebuilder in the garage just in case the 360 gives up the Ghost.) Any ideas about what causes the pressure drop?

Post by **DuckRyder** » Wed Oct 15, 2008 8:28 pm

Drainback holes in the head clear?

Does overfilling it one quart help?

Post by **Ranchero50** » Wed Oct 15, 2008 8:52 pm

Yeah, methinks the old umbrella valve seals have dissentigrated and made there way into the drainbacks. Been there, a pain to clean out

Jamie

69timemachine · Post by **69timemachine** » Wed Oct 15, 2008 9:50 pm

Maybe the spring in the oil pump pressure regulator is getting weak? Is that the original oil pump? Just an idea.

mrtleavitt · Post by **mrtleavitt** » Wed Oct 15, 2008 10:26 pm

My 390 does the same thing. I've never worried about it. It just makes sense as the oil gets hotter it will definitely get thinner creating less pressure. As long as the guage doesn't get too low (probably below 1/4) it should be fine. I've never had an old ford not do that.

Kurt Combs · Post by **Kurt Combs** » Thu Oct 16, 2008 12:27 am

Thanks for the replies. The pressure doesn't get too low, if you trust a Ford guage. I think I will live with it until I rebuild the 390 in the future. The truck just keeps running about the same and I drive it a lot. The 390 is just sitting in my garage waiting for the 360 to self-destruct and then I will have a good core to rebuild.

peanutman · Post by **peanutman** » Thu Oct 16, 2008 9:25 am

My orig heat gauge was going bonkers. Changed the thermo, sending unit, printed circuit,voltage stab and wire to gauge-same thing. went to az and bought a mech heat gauge and problem was solved. I don't trust these old ford gauges

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oil pressure drops at high speed

oil pressure drops at high speed

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