Sorry I first posted this in the Barracuda forum when it should have been here.

I rebuilt a 360 and it runs great (12.80's in a 3400 lb. Cuda) and the oil pressure is normal when cruising (30 psi. @ idle when hot and 58-60 psi down the hwy) but when I stop to torque it up for a blast the oil pressure goes down to 30 lbs. and just stays there as long as I'm into it for the full 1/4. It never builds any more pressure than 30-35 psi like it does when cruising normally. If I'm already running down the road and the oil pressure is up to 58-60 and jump on it it stays up fine as long as I'm into it. It's only when I torque it up (got a 3,000 stall) from a stop that it never builds more pressure unless I bring the rpm's up real slow. Then it goes to about 40 psi. I put about 900 miles on it and finally got around to yanking it back out and apart for inspection and frankly expected to see toasted bearings and find a faulty oil pump relief valve. Much to my surprise I couldn't find any problem at all. Every rod and main bearing still checked out at .002 clearance and bearings looked just like the day I put them in and the oil pump checked out fine on my test jig. I was really surprised to see the bearings were still like new cause I didn't take it easy on it even though the pressure showed low under acceleration.

Things I checked when apart include all bearing clearances (every one checked .002). Rod side clearance (.019-.022). Disassembled the oil pump and checked the relief valve and found no problem. Lifter bore size is .905-.906 which is a little loose but is this loose enough to cause this problem??? Checked to make sure all block plugs are in and they are.

I also tried adding up to 2 qts. of oil extra just to make sure it wasn't starving for oil under acceleration and it had no affect.

I'm running a Melling HV pump with the standard pressure spring and a Moroso pickup for stock pan and set to 1/4" clearance to pan. Also have a factory 360 windage tray. Stock oil pan. De-burred all the oil drain back holes.

Anybody else seen a problem like this or have an what it can be? I've rebuilt many engines over the last 25 yrs. but never ran into this problem.  

Oil pressure problems can be grouped into 2 main categories.

First, lack of pumping. This could be the oil pump clearances themselves, the pressure relief valve, or an oiling system problem like sucking the pan dry, or otherwise cavitating the oil pump (sucking air). Sometimes there will be a crack in the pickup, but usually oiling problems under acceleration have to do with either g-forces sloshing the oil to the rear of the pan, not enough oil capacity, or the oil isn't returning to the pan quickly enough. You mention a high-volume oil pump and stock pan, with low gears and a loose stall, this could suck the pan dry. Adding 2 extra quarts is an ok test for this problem, but will cause windage which could also cause the pump to cavitate.

The second type of oil pressure problem is pressure bleed-off. This means the pump is pumping, but too much oil is bleeding by the bearings, lifters, rockers, etc. This is checked by making sure all clearances are proper, check cam bearing clearances as well. Also, check that the lifters aren't coming so far out of the bore that the relief is allowed to show. I've even seen cracked blocks or heads be the cause of low oil pressure. If you had the block magna-fluxed and pressure tested, you could determine if it's cracked.

Hope this helps.  

Thanks alot for the reply Badfish. You raise some good points. I knew I was taking my chances with the stock pan and hv pump and gears, etc... but since it does it even when I just torque it up before the car actually moves I have a hard time seeing that being the problem. That's why I did the extra 1 then 2 qts. of oil test. I did drain it back down since it never helped. Since I allready verified (twice) the bearing clearances are ok (allI didn't check the cam bearings since their hard to check with an assembled engine).
Unfortunately I skipped the block magnaflux test since it came out of a car that was holding coolant fine. I never thought to test for cracks for any other reason. Now I wish I would have done that.
The pump pickup is a new unit and I did look it over good before installation and didn't see any cracks but I won't rule that out at the moment until I inspect it again.
I had a smaller cam in it at first (only .488 lift) and it did the same thing so I kinda doubt the cam lift is causing the lifters to come up exposing the oil slots but I will double check that also.
One thing I didn't put in my first post is the lifter bores mic'd out at .9057-.906 which is slightly out of spec as the FSM says .9055 is the limit. This clearance puts the lifters at .0017-.002 clearance. I wonder if this the cause??

Thanks again for the time taken to help Badfish.

Fishy68  

I know it sounds funny but I have had several fram  oil filters do just what you are saying.I have found that the folds lay on top of each other and slow oil flow down. Also what kind of oil are you using.  

I'm using Valvolie VR1 30 weight and a Napa gold filter. I have read that the Napa filter is made by Wix so I think it's a good one but what the heck, I might just give a different filter a try because your the second guy in the last couple days that mentioned he has seen that. I didn't ask him what filter he was refering to though.

Thanks  

I had a similar experience with a newer filter off a late model 360, put on a fram problem solved.  

Extra oil is a danger unless you have a very deep pan. I do not think the 30 psi is a very serious problem unless you only use the car for the strip.  Your .002 bearing clearence is probably the source of your oil pressure loss.  This sould be .0015 or less unless you are running a thick base weight oil, say 50 wt racing oil.  Your rod side clearence seems a little high also.  Try running the engine with straight 50 wt and see if the pressure improves.  Make sure the oil is well warmed up before you flog it.  Does the block have new cam bearings?
Don