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Oil pressure dropping at high RPM!!

8K views 16 replies 7 participants last post by  DeepRoots 
#1 ·
HI Guys, have a centrifugal supercharged stock stroke 460 that is dropping oil pressure from 65 pounds at 2000 RPM on the foot brake to about 35 pounds after the engine speed rises above 5000 RPM (it hits the chip at 6200), it stays at 35 PSI for the whole 1/8 mile, and pops back up as I lift and engine speed drops. Engine specifics are main/rod bearing clearances of .003 and .0028, Joe Gibbs 15-40 oil, Canton 15-774 (Fox body & Cobra engine swap pan) road race style pan with 4 trapdoors and dual sumps, melling M84DHV pump, Canton pickup (all came bundled in a kit). I did make sure pickup wasn't too close to bottom of pan.


Would really love to hear some opinions about correcting this, Thanks!
 
#3 ·
If it's a front or mid sump pan the oil can rush to the back of the pan away from the pickup during acceleration.
 
#6 ·
If you don't loose oil pressure free-revving it in neutral but you do while accelerating, then either the oil is rushing away from the pickup during acceleration (maybe try welding baffles in the sump?) or you have internal clearances that are opening up under load. Your connecting rod or main bearing caps may be distorting under load causing a drop in oil pressure.
 
#9 ·
The 460 has the same oiling problems as the 351C, and needs restrictors installed in the block to reduce oil flow to the cam. I also restrict and block off oil passages at the front main. But if your rod and mains look fine, maybe try 20W-50 oil and don't worry about it. Ed
 
#10 ·
that is NOT a pan id use for drag racing,you said not too close? Well how far away is it now?

is there enough oil in it?
 
#11 · (Edited)
The pan is necessary because I put a Rod & Custom front end in it last winter. This pan is the only one that clears the (new) engine crossmember and PS rack. I have about 1/8 inch between pan and rack, and the hood actually touches my blow thru hat, so not much extra room in engine compartment.

I dont recall exactly what the pickup height is, but it is in between what Canton said, which is between 3/8 and 1/2 off pan.

I understand people mod the oiling system of high RPM 385 motors, but at a max of 6200, most say I shouldnt need to do restrictors or external lines. Plus I didn't have this pressure loss with the last oil pan.
I believe the car had 7 quarts of oil in it when I noticed pressure problems. This is a nominal 6 quart pan...

I had a pleasant phone conversation with Paul Kane of High Flow Dynamics (Thanks Paul!), he was familiar with my oil pan, and said it is a pretty good pan. He suggested I check to make sure the rear pan baffle was keeping oil from going straight up the back of the pan into the crank under acceleration and causing windage. The baffle in my pan is fully welded across the back with no gap, so I dont any issue there. His only other suggestion was since the pan is so close to the crank in the middle section, I could try a screen or a tray to stop windage. The screen is what I'm planning on doing, if I can get one that will fit in the limited space.

Thanks for your input guys!
PS The car is running 6.59 @ 106.2 right now. Yea, in the 1/8th.....
 
#13 ·
The pan is rated at 6 quarts, the system total should be 7, according to Canton. I had 7 in the pan, PLUS the 1 quart filter. So, 8-ish.
As far as the pickup height, I will measure it and plan to put it at the bottom of the Canton spec.
Engine was dynoed with this pan, had no oil pressure issues.
 
#14 ·
engine is level on the dyno,and its not ran @ rpm as long

well i tried to help, maybe someone else can tell you what you want to hear?

good luck
 
#17 ·
I'm sure he's got some great info.

From my own point of view, the road race pans are neat. I'd have to wonder in a high volume drag race environment how much oil leaves the enclosed area vs how much can enter the traps.
On the dyno it'd be fine as all four traps are moving oil toward the pickups. I'd worry about the hard launch of drag racing because I'd think the oil can only enter via one trapdoor.

either way, good luck
 
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