5 liter (E150) oil pressure drop

its not a bad truck at all. 16 mpg highway with a tail wind @62mph. Nice stainless exhaust. It has a nice little rumble. I had the EOD trans rebuilt a few years ago so i'm a little upside down on value/cost and would put forth one more effort to find oil pressure problem. when cold oil pressure is fine (for a ford). I sould hook a gauge up to OP sender so that I'm understanding #'s and not degrees of low to high. if i do ten or so o-40 mph "dashes" up my street, oil pressure drops to the extent the lifters pump down. I've not got a really good idea of the cause. what I have done is let the truck sit for 2 months with kero in engine. After dumping and putting in 5/ 30 ( idont wish to trigger a oil weight debate) started it let it get normal temp and dropped this oil, and then put 10 30 in, as im still not using the truck just trying to flush it. I am wondering if it could be decaying plastic timing gears (engine has 170K mi) or sludge? or oil pump? Once again the oil pressure is good on startup so i wouldnt immediately think bearing wear. Any ideas? THe ps is the oil pan cant really be removed without raising the engine 13" so ive read so it will be a big commitment to see that. I suppose timing gear wear is possible, but now i wish i've done an otopsy on the old oil filter to see whats been floating around down there. Sorry for the long post i hope someone can help! boxcar- NNJ

The problem is going to be one of the 2 that you've mentioned. Either a blocked oil pickup tube or worn bearings. The only way to tell is to remove the oil pan and look. There's no real need, at this point, to install a mechanical gauge as you said the lifters collapse. I would really suggest pulling the motor and doing a thorough inspection on the entire thing. At 170K you might want to consider a good used motor or even a crate motor depending on the condition of the rest of the truck. As far as being "upside down", on a used vehicle at this mileage one major repair can get you there. If the truck is in otherwise good condition and reliable, "upside down" should not be a consideration. The consideration should be "is it worth it to ME to replace the motor in this truck?".