For those of you who haven't been following my problem for months now, http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=5;t=002683
It started when the pick up broke off. I replaced the pump and pick up, the pressure would drop when I got on it. Fine at idle and cruising 25/60 psi. I replaced the main and rod bearings, still droped when I get on it. Replace the oil psi gauge. Changed different weight oils, brand filters, different brand oil pump, High volume to a standard volume pump. I took the motor out and had it rebuilt. Had my builder set the pick up to 3/8's off the pan. Still droped when I would get into it, after the rebuild. My builder did say he didn't see anything that looked to be my problem, but if I did still have the problem, it wasn't my short block.

Sat. I went up to see a friend (jakeshoe) and while I was there, I took him for a ride to show what my oil psi was doing. Well, it didn't do what is has been doing for months now. I got home and checked the oil and it was a quart low, (freah motor still, 700 miles on it since rebuild) so I added and went around the block, the psi problem was back. After thinking about it for a sec., I took a quart back out and the psi is fine again. That means I am running 4 quarts in the motor. When changing oil, I am putting 5 quarts in like I always have with any of my motors and a standard one quart filter. How is the extra oil making my psi go down? Is my pan the problem? I have a stock pan on it and it worked fine on the motor for about 8 months before all this started.

As of now, when I am racing it/getting on it. the pressure goes to about 65 psi, drops to 55ish psi for a nano sec, then go back up to 65 psi. So, is it something to do with my pan? Any thoughts from the experts?

Thanks guys for helping me with the whole problem for the past few months.

Michael

Are you running a windage tray? Is this an aftermarket pan? I had a similar problem with a Milodon 6 qt pan. If I ran it with 6 qts, it would start dropping pressure at 5500 rpm. If I ran it a quart low it would not drop pressure until 6000 rpm. I did not have a windage tray. A windage tray will be my next addition when I find the time. I didn't think I needed one since I shift at 5800 rpms and I did not have this problem when I had a stock pan on the engine. I thought the aftermarket pan would be a nice upgrade since the plug on my stock pan was double oversize. After this ordeal, I looked at the stock pan and it has more oil control features than the aftermarket pan. My theory is that the aftermarket pan w/o a tray allows the oil to get picked up by the crank and splash oil away from the pickup at high rpms. Dropping the oil level moves the oil away from the crank buying you a few more rpms before the problem occurs.

I am running a stock pan and no windage tray. I just can't understand why I never needed one before and now I do? My psi drop is right when I get onit, no matter what the rpm. I was thinking of getting a big bad pans to see if that would help. I did get a an idea of running a 2 quart oil filter and then I could have my volume back, but still show low on the dip stick.

Now that I think of it more, it does sound like something like the crank picking up the oil creating the psi drop. Oil control problem. hmmmm......

Michael

Since the problem appeared after replacing the pump and the pickup, did you try to replace the pump and pickup with the same brand as you originally had in there before the problem started? I did read that you switched pump brands. Are you sure that you are using the stock length pickup?

I replaced the pump because my pressure was droping off when I got on it. Upon taking the filter apart to inspect it, thats when I seen metal strands in the filter, I pulled the pan and the pick up had broken off, not fell off, but broke off. It was a 3 year old pump and I guess the pick up had fatigued. The strands were from the screen of the pick up. I have double checked with each pump I have had to make sure I had the right pump pick up. (Called manufacture)I replaced it with the same one I had before, a Melling HV, and then I tried a Moroso SV pump and the psi was even worse, would drop right to 0 when I got on it. So after a few weeks, I put the Melling back on. It gave me way better psi, like atleast 20 while getting on it. I'm realling thinking its a windage problem, not sure why it didn't do this for the 1st 8 months I raced with it tho.?.? Thanks for the input guys.

Michael

I've been seeing the same problems. I had the oil to full and the pressure didn't go much above about 45psi and it never seemed really steady. I had added another liter without any change. So, after reading this, I dropped out about 2 liters (to add mark) and it held steady at 60psi at 4000rpm. I need to test drive it in the near future.

I have a so called HVHP pump but I installed the standard spring in it so that shouldn't be the problem. I have a stock pan without any other oil control. After this, I think that a crank scraper or windage tray will go in my next engine. I believe the oil is being picked up by the crank. I've read before that the oil can literally wrap around the crank but I don't know if that is true. Need a oil pan with a window.

Peter

Originally posted by Peter F.:
Need a oil pan with a window.
Man that would help alot huh!!

Old- I would swap in a new oil presure gauge if you have not already ! I have been stung by faulty gauges once or twice in the last 20 years!
Good Luck!

Originally posted by 67johnny:
Old- I would swap in a new oil presure gauge if you have not already ! I have been stung by faulty gauges once or twice in the last 20 years!
Good Luck! Good idea, or it could be the sending unit.
You might try a new one.

Believe it or not, old worn out cam bearings will cause the problem you're describing. Were your cam bearings replaced during your rebuild and were they installed in their correct locations?
(They are somewhat different in size, front to rear.)

Yes, the rebuild included the cam bearings and I think my motor builder is smart enough to install them right. I have changed gauges and sending units 3 times, so thats ruled out. Its got to be a windage/oil control problem, take a quart out and the psi is fine.???

Michael