Separate names with a comma.
Discussion in 'Engine Topic' started by lumpy12, Feb 1, 2014.
Drain a qt out and see if it fixes it.
That's a great idea! it would maybe answer 2 of the possible causes. If its cavitation , the pressure should stay good. If its the pick-up, you may not have any pressure on fire up.
I'm not sure if this is the correct answer, just an educated guess....
The pressure would most likely drop because there is no restriction from the filter, just a direct flow back into the pan.
I can't see how it could be going back into the pan. From the pump it would hit the filter and then go through the bypass and into the oil galleys.
Cold, it bypasses the filter and sends 60#'s to the motor. Hot, if it's bypassing the filter, I would think it would still send more than 20# to the motor at 5000rpm.
Regardless, this is an interesting thing going on.
I get to try:
different filter bypass
poke around in the pan for a loose or slipped pickup
and maybe even pull the pan --- oh joy!
My buddy had a 475 hp 383 that did the same identical thing. We never heard lifter clatter, so we just left it.
Not sure exactly how the oil flows through the block, I was just guessing. Sorry.
No, that's a really good guess and it could be right on the money. I don't know how the oil does what it does, especially when something goofy is going on like mine
This is a mystery motor as it came with the car. It has an Edelbrock top end kit but the stock pan and I worry about sucking air if I ever hit a road course, so a road race pan is already on my wish list!
I've been really curious about what's inside (crank, rods, pistons, oil pump, 4bolt/2bolt mains, studs, etc.) Worst case is I pull it and end up doing it all right.
I have the same thing happen on my current engine in my '71 RS/SS 350 with this engine built with Edelbrock top end, hi volume pump, 2 bolt mains, and drives fine. I was told as long as I have pressure do not worry and just drive it. I do not drive it a lot but it has been like that for several years. Tried different filters, oil levels, etc. I would be interested to see what you find out.
I start in on the tinkering and testing tomorrow. Weather sucks for test driving however, but I'm really curious to find out what's up
The sending unit will more likely fail when the motor is hot rather than cold. Too bad it isn't standard practice to spot weld the oil pan pickup. I'll put my $ on the oil pressure sending unit or wire. Check the wiring diagrams too, maybe a bad GND.
No,there is a bypass on the pump too. Once it hits the limit the pressure overpowers a spring on the side of the pump and it pumps anything over that pressure back into the pan. I tried shimming the spring once and had oil pressure that past the guage max,and would blow the rings out of the filter. If the spring were broken it would bypass at a much lower pressure. The bypass can only pass a limited amount of oil,so eventually the pressure goes past the bypass point because the bypass cant release the pressure fast enough. Most pumps bypass at 35 to 45 psi,but because of how much volume a chevy pump(even a stock one) can push,the pressure can still go way higher then that because the bypass cant release the oil fast enough once the pump reaches it's max flow.