Washed Away

Well here is the situation. 496 mark iv block. 80 psi oil pressure (on mech gauge at oil filter housing port, inlet) when cold. warmed up idle pressure 35-40. 60 psi at rpm warm. After a long run which does not have to a banzai run, just a normal cruise (3500-4500), oil pressure drops to 8-10 psi. After 3-5 mins of idle pressure back up to 30-35psi. Rev motor back up when reading 8-10 psi and pressure rises ok.

motor specs:
496ci
scat 4340 4.25 crank
cat h-beam rods
keith black flatops
federal mogul hp bearings w/proper chamfer
f/m high volume pump
comp cam and lifters/hyd
comp roller tip rockers
stock mercruiser pan w/ 1 qt kickouts welded on for 8 qts
fram filter not hp

All clearences where checked by machine shop and doubled w/plastigage at home. scat crank clearences were spot on but the cat rods needed cleaned up. clearences are o.k. the only oiling mods were a SMALL hole drilled in front gallery plug for cam chain oiling. The lifters where set at a quater turn down from zero.

My thoughts are that I am running the oil level at the full mark on stock dipstick and the .25 inch strocker is whipping the oil into foam. Haven't tried running a lower setting yet. The block has the stock windage tray. Maybe a crank scapper? Have a little to much lifter noise at normal psi, maybe not enough lifter preload?

I am running 10-50 mobile1 oil.

paradigm shift

What is your oil temperature?
Are you running an oil cooler?

I am running a 4.5 stroke with stock 8qt pan and windage tray. I have had no oil problems to date. Did you double check pan capacity after welding kickouts in. To much oil will cause foaming but you should beable to see it on the dip stick. Oil temperature running high can also cause low pressure and then cools down enough at idle. You might try another 1/4 turn down on lifter preload. Flat tappet or Roller lifters?

Washed Away

The oil pan is not the cast pan that I have seen. It is the stamped pan design. The oil height is the same as before but the kick outs were welded on. Same pan depth but wider sump. I do not have a oil temp gauge.
I am running the stock mercruiser oil cooler. Presssure is fine until I throttle back. Comp Xtreme Marine flat tappet.

Audiofn

Any chance you have to much oil in it? To muck your crank will spash in the oil and cause this.

Jon

Mbam

What exactly are the clearances?

blue thunder

Yes, what were the clearances? Particulary the mains. I would cut open the oil filter to look for the flakes of death. If all is ok, install oil temp gage. Should have one anyway. I suspect your cooler is too small and you didn't preload your lifters enough. I usually go about 5/8 turn on lifter preload. Once the oil temp gage is installed you can take runs with less oil than you are running now to see if the crank was splashing the oil and creating high temps. If your pump was cavitating you would see the oil pressure drop while running at speed. Doesn't sound like that is the case.

Dave

MACDAD260

My guess is that you need a bigger oil cooler. That 496 runs a lot hotter than a 454. Horsepower makes heat. The oil is what keeps the pistons cool so the oil needs to be cooled more with more HP. Even if you are having some foaming problems you will still need a bigger cooler. I swapped a 330 with a 502 Mag. I have a 2" X 12" cooler and my oil will get to 250* and the pressure drops at idle just as you have described. I am going to put an Eddie Marine 3" X 12" cooler on it this winter. I hope that cures the problem for me.

Good Luck.

Reed Jensen

I would suggest putting a temp sensor in the pan. I prefer to measure the oil where it is going to be hottest. Some people put the sensor in the hole in the block just above where the stock filter fits. If you measure the oil temp after it has already passed through the cooler..... you won't have any idea what the engine is doing. If there is an issue inside the engine... piston overheating because of lean mixture or detonation.... you will see it by the temp spike in the oil.... but if you are checking the oil after it has been cooled... you won't see the problem. I don't get alarmed about oil temp until it reaches over 250 degrees. Oil reaches it maximum 'lubricity' at 200 degrees. If you put on a cooler that is too big.... your oil pressure will increase.... but most of the oil is flowing out the pressure relief valve in the pump rather than passing through the bearings. Hot oil is like water..... it takes the path of least resistance. I'd rather have hot thin oil that is making it's way to the wear surfaces of the engine than cold thick oil that isn't going anywhere but circulating from the relief port back to the pump. The idiot that plumbed my boat put a 4" x 24" double pass cooler in the system... even at full boost the oil temp would never get above 75 degrees .... and then the dope put in straight 50 weight oil.... needless to say the bearings failed in 5 hours and the engines had to be redone. After some serious replumbing and rebuilding of both engines... I sorted out the oiling system and the boat ran great and never had any of the "flakes of death" in the oil as Big Thunder described. I found out the hard way that the supposed 'expert' that built the engines and rigged the boat was better at beating his own drum than actually knowing what he was doing. One other thing to consider is what kind of oil filter you are running.... does the engine have the stock oil filter bypass? If not you have to run a filter that has a built in bypass such as a fram HP6. You can actually see the bypass valve on the HP6 by looking down the inside of the filter..... it is the brown button at the bottom.

blue thunder

My temp senders are in the remote filter pad. This is in the path the oil takes after leaving the pump but before going to the cooler. You get almost the same reading as in the pan. Reed is right on with the 250F being max reasonable oil temp. My goal this year is to have oil temps that run around 200F and only get over 212 w/ a WOT blast but never exceed 220. I'll bet your oil temps are getting in the upper 200s Washed Away which is bad.

Dave

H2Xmark

what size hole did you drill in the galley plug to oil the chain? if to big a hole it can cause a oil pressure problem like you talk about[ i would think 1/16 is as big as you would want to go here]