Oil cavatation? looking for clues
 

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.

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?

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.

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

Jon

What exactly are the clearances?

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

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.

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.

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

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]

Another thing to check is the fit of the distributer to the block..... if the distributer is too loose in the block it will allow the oil that is intended to go to the lifters on the right side of engine to just leak back into the sump. Hence low oil pressure..... again.... oil is like water.... it takes the path of least resistance. Anywhere oil is bled off it will decrease the pressure. The entire oiling system is like a controlled leak.... you just want it to leak in the right places! Good oil won't begin to coke up until over 400f. I had an air cooled motorcycle and the oil on that engine ran 350 f ! I could have deep fried chicken in it! The oil didn't discolor or burn... it just broke down quickly and would lose it's lubrication properties, so I had to change it often.

Where are you measuring the pressure?

Here is a picture of a main bearing that was in an engine that the oil temp got to 280F. Unfortunately it was dino oil (straight 40) and couldn't take the heat. It broke down, lost it's cushioning ability and caused crank to bearing contact. This engine still ran strong and had 60psi warm at 3500rpm. Idling it was around 10psi. Before the hard run it stayed about 40psi warm idling. Cutting open the filter revealed the flakes of death but also saved me a lot of money because I didn't spin a bearing.

MMMMMMMMM....... Flakes of death! lol So many times people get "hung up" on oil pressure. I'm beginning to think some guys measure the length of their **** by how much oil pressure their engine makes! Boat guys talk about 60 psi and 80 psi... I work on old Aston Martin engines... AND THOSE GUYS DO MEASURE THE LENGTH OF THEIR ****'S BY THEIR OIL PRESSURE! A freshly rebuilt DB5 or DB6 engine will make 125 psi .... even when hot! These guys are crazy. All this extra pressure is an attempt to stave off bearing and cam failure because of poor design from the factory. I like to measure the oil pressure on a tall block at the hole at the very front of the block.... by the right head. It is the very furthest from the pump.... and thusly the weakest point... I know that if I have pressure there.... I have pressure everywhere. I ran 10-40 dino oil and after a high speed run,,,when the engines came down to idle.... the most oil pressure I would see was about 25 lbs. I didn't worry about it because I knew the main and rod bearings were getting oiled.

Here is something for you guys to ponder. If you are running a pump in the sump... ( melling, chev, merc, etc etc) . These pumps are designed with space limitations. The pump was originally designed to pick up warm oil,10-40 w, push it through a filter ( most of which goes through the bypass) and down the passage in the block to the main bearings, through the crank and to the rod bearings, along with oil being bled off to the cam bearings, lifters, rockers, etc. The total volumn of the oil being pushed by the pump is about 1 1/2 qts. Now that little pump is put in a boat.... and for the sake of tempurature control.... that oil is being pushed out the block,through a hose, up to a remote filter, down another hose, through a remote cooler, back through another hose, and then into the block. Total volumn of oil now having to be pushed..... about 3 qts, plus it has to be pushed through about 10 feet of hose. Right now that pump has to keep moving twice the volumn of oil flowing before it lubricates anything. Starting to see my point? A lot of the oil can't be pushed fast enough so it just flows out of the pump through the pressure relief valve. If you measure the oil where it first comes out of the block.... it will be high, because it is the static pressure within the pump. But by the time it gets out to the bearings,,,, it isn't much. Try this experiment. Try blowing the water through a 25 foot garden hose. I'm sure you will agree that no matter how hard you blow.... there isn't much water coming out the other end..... I prefer to run a thinner oil at a hotter temp so that it flows easier.... Look at the oils they run in new Chev car engines.... 5-30 oil... and those engines don't suffer bearing failures all the time like boat engines do.

I think people run higher viscosity oils in boats because the valve train creates so much more oil temp than does automotive. The trick is to not run hard until the oil is up to normal operating temp and therefore the viscosity is appropriate for the flow restriction of the marine system.

I guess we are talking to ourselves now because washed away seems to have disappeared. :rolleyes:

Dave

I'd like to know your theory on why the valve train in a boat motor is hotter than in an automotive engine. Reed

Higher sustained rpm in a boat. What are you thinking?

That wasn't much theory I guess. Maybe this will be better: Higher rpm allow less seat time for the valves so they run hotter. Also the valve train itself spends more time (due to rpm) under the load of the valve spring. All in all, much more heat than typical auto.

Dave

MMM.... yeah,,,, the exhaust valves do run hotter. Especially if the motor is blown. Intakes don't run that much hotter.. a little due to the cycles and extra heat from supercharging and there is a little more heat from hysteresis from the springs. But the load on the cam bearings and rocker faces remains constant. Just more friction from movement. I would think that if you held an auto engine on a grade for a couple of hours you would see comparable heat.... ok... you win... boat valve train does run hotter. :D But you still have to have oil flow from the pushrods up to the top of the engine to dissapate the heat into the oil.... So I still think thinner oil is better! Just so that you know... the lifters in my motors were crane roller hydraulics, and the tech staff at Crane told me those lifters were designed for auto engines and will not pump any oil up to the rockers if it was thicker than 10-40 at 200 degrees f. So I was especially pissed off at the guy that put straight 50 w oil in the engines. I wondered at the time why the roller rockers were worn out after 5 hours too.After I spoke to the tech department at Crane I knew!

I agree Reed. An auto engine would do the same thing under the same condition. But if that was the case, I would run higher viscosity oil in the auto engine as well. I certainly don't agree with the straight 50 wgt oil your engines had. Way too thick for pumping when cold. I do like the 15-50 synthetics though. It will flow comparable to the 10w-40 you mentioned and is what I run since producing the bearing in the picture above.

Dave

My guess to, stick to the basics 1st before trying to find some exotic problem/solution, get an oil temp guage and put the sender on the oil fliter block where merc does it is qucik and easy and temp will not be dif by more than a couple degrees if any than what you measure in the pan and you can't see that on a guage when running at WOT anyways . It will tell you if your at 240 or less or 250 or more which is what you need to know.

The 300hp 454 oil cooler is like 2x 7", the 385hp 454mag 10", the 415hp 502 mag 13"
if you increased your HP signifigantly you need to increase your cooling to match.

Because you are capable of sustaining 60 lb pressure @ reduced engine speed, and that pressure drops off at elevated rpm’s, leads me to believe that you may have a supply/delivery problem (aeration). Excessive bearing clearance would typically depress pressure across the board, rather than vary pressure by demand, although clearance and/or windage are a distinct possibility.
I have seen instances where the pick-up being located to close to the pan resulted in a similar situation to yours. The pick-up draws its oil supply from beneath; being to close to the pan severely restricts the volume (creating a low pressure area beneath the pick-up) of oil available to the pump. As rpm’s increase, demand does also. When that supply is restricted the oil becomes aerated due to cavitation, the oil becomes a vapor, heats, and at this point the volume the pump is capable of handling is diminished resulting in lower pressure and incomplete lubrication. As you reduce the rpm, demand decreases, supply stabilizes, aeration bleeds out, and pressure returns.
I would suggest you check:
The clearance from pan to pick-up
Did the pan distort or warp during welding?
Is the pick up screen clogged?
Is the pick-up securely attached to the pump?
Bypass spring
Is the oil pump is properly torqued to the rear main?
Hope this helps,
Bob

Hey guys. Great ideas here. Haven't thought about the oil temp. Sounds like a gauge is in order this spring. I'll try to answer some of the questions. Bearing clerances ran .002 on the rods, .002-.0025 an the mains, can't remember rod side clearance but it doesnt stick out in my mind as a worry. I am running mobile 1 after a breakin with regular 10-40 oil. No "death flakes" after second oil change ( still regular oil, this is when I switch to synthetic). Boat is in storage so I'll be very careful when checking filter in the spring rollout. Engine is based off a 365 Mag setup. It is this oil cooler that I have. Oil pan did have some warpage after welding, so I spent some time with clay on my pan to pickup clearences (.25"). The pickup was also welded to new pump (spring removed during welding). The hole in the gallery plug was smaller than 1/16". The distributer is factory stock. The pressure also only drop at idle ( not during run) after longer runs, then slowly rises.

The engine was built for a reliable 500 or so hp @ 5000-5200. I never oil pressure or temp problems with the 365. The block had 200 hours before the tear down, and now has 10-15 hrs on the new build. I have probably added 130-150 hp to the motor. The oil temp problem may be the place to start. I thought the stock cooler would have given me enough protection.

Did I read that a temp gauge can be plumbed at the oil filter housing inlet? (this is where the mech oil psi gauge is)

There is a big difference between the little sparkly bits (almost microscopic) and "flakes of death". Flakes of death are very visible bearing material and are actually small flakes @ 1/32 of an inch across. Good luck!

Oil temp sensor can be placed in the remote oil filter block ( where the oil filter is there is an extra hole there just remove the brass plug)

Merc uses a 2" longer oil cooler on the 415hp 502 mag than on the 365hp 454. The hp500 cooler is like 17" long

I had the same problem and it turned out my high volume oil pump was sucking the pan dry. I went with a standard volume/pressure pump and it cured the problem.

jhnrckr may be on to something.
I ran into this on a Ford FE motor. High volume pump sucked the 10 qt pan dry, flooded the top end with oil. And that was at 3000 rpm.
Worth checking out.
Gary

I can't imagine an engine with 10 qts of oil up in the valve cover area. Were the return holes plugged? The valve covers would have been filled up totally. I think the oil was just getting aerated and with the bubbles it becomes compressible and the pump couldn't handle it.

Reed Jensen
I wouldn't have believed it either if I had not seen it. I think part of it is lack of adequate return volume, and some may be pickup/pan design as well on those engines. Inadequate pump/pan clearace could result in aeration with the higher volume pump
BTW, I'm not the only one who had encountered this on FEs, see:
http://groups.yahoo.com/group/cccommander/message/13735

Thanks for the info.... I guess on the ford engines the return area was restricted by the manifold gasket. Those engines to my recollection , had the oil piped up to the rocker shafts. On the chev engines the oil is pumped up the rods... Most of the restriction for oil flow to the upper part of the chev is through the lifters. On the crane roller hydraulic lifters there is so little oil passing that if you run anything thicker than 10-40 they don't lubricate the rocker well enough. But there are "passages" between the lifter areas and the lower crankcase that can collect lots of oil from what is flung off the crankshaft. It may be possible that oil is pooling there, but I'm still skeptical that 10 qts can collect in the rocker covers.

it sure sounds a lot like your pump bypass is sticking open. Make sure the pickup is 1/2 inch from bottom of the pan to avoid cavitation and foam

Roby

Is it possible that the lifter valley can be holding oil under high pressure too? I know that when I switch to a standard volume pump all my problems went away, solid pressure from idle to 5600+ RPMs.

Washedaway,
When you added the kick-outs did you re baffle the pan, add any diverters or trapdoors?
Bob

Rmbuilder,

No I didn't add any other trap doors or baffles. I did deburr all the oil drain back holes and slots in the block.

I don't know wher this will end in the spring, but some spring time testing is due with oil levels ( a 1/2 to a quart lower on stick), maybe a quick shut down and watching the level rise on the stick. The pressure never seemed to flucuate at crusing rpms (3500-4000). Maybe a return to a stock type pump is worth a try.

On the oil filter bypass we hallway's plugged it. made all the oil run thru the filter ,just careful not to rev motor when oil was cold .I always run the Moroso pumps with the anti cavitation grooves in it. I think mellings new design pumps have this ,they do require a deferent pick up.on my boat blower engine it had 90 psi and never sucked the pan dry even at 7250 Rpm. My Chevelle small block it has 80 psi on the Moroso pump in a 10-12 sec.pass down the track at 7800rpm it does not suck the pan dry.contradiction?Smokey Yunic allway"s said for every 1000RPM all you need is 10psi so 6000 is 60 psi.

On Oil level sounds like might want to run a quart low.see if the crank is picking up the oil .On My Chevelle it has a 7 quart Canton oil pan on it and testing it on the bench with 7 quarts in it it was above the windage tray.even with the oil filter consideration capacity, It might be that close on yours?remember it does not sit level in a boat.

What about the oil pump matting to the rear main cap ,could some be spraying (leaking) out?

I have seen rod side clearance do it. you did say you had to do some work to the rods?

It has to be windage which would make aeration, but what is causing it?

You said it goes down when you let out of it .I don't think this is it but.
On my Camaro drag car it had a Moroso T sump pan on it and when on the breaks hard the oil pressure would go down to 20 psi. so the oil was moving forward in the pan oil pump sucking some air. I bought a Jeff Johnston Billet fabrication oil pan with full kick out ,flat bottom .It looks like a 14 quart pan its so big . I only run 7 quarts in the pan and no problems any more.even with the oil level that low.

Iwas wondering how lifter preload might cause this problem. I owned a 24' panther that had the same problem.Just started it had 65psi warmed up 55psi after a run than idle 10to 15 psi. let idle for 10 to 15 mins and back up to 55 TRIED EVERYTHING MENTIONED in this thread except lifter preload. I always adj 1/2 turn maybe it was never enough. Can anyone explain how that would cause this problem. Never did cure that problem just ran it that way for 3 years than sold boat and that guy ran it for a few more. But it did always make me worry and not enjoy the boat totally

I have had windage problems in the past and they showed as a drop in oil pressure at elevated rpm. Also, when I had windage problem I could smell oil burning as it hit the underside of the hot pistons. It was an unpleasant situation. Well, I have fixed the windage problem, studied the bypass valve plugging option and decided to leave bypass in, buy larger coolers and replumb oil lines to eliminate 90* elbows. I have been having the same problem with oil temps.

Lifter pre-load will not cause oil pressure problems.

Dave

What windage tray is the best? I presently have Dooley 8 qt. pans with a sheet metal tray. I am considering going to a Milodon screen type with a crank scraper. While this may work well in cars, I'm worried the screen won't control the oil in rough water.

Ya gotta love engines. I've seen stock rebuilds blow up in a week and buddies beaters drive for years without anything but gas and a quart of cheap oil every other fill up. Its gotta be some sort of addiction that makes a person tear into a perfectly good running motor and try to make it better (faster, stronger, quicker). I'll give ya some more background on the engine (block really). The boat has 350 hrs on it. The guy I bought it from bought it at a repo auction with a blown 365 mag. He bought a 330 long block and had it installed. (At appox. 75-100 hrs I believe). I bought the boat and threw a cam and intake on it and ran it for a year. This last spring I pulled the motor and rebuilt to a 496 (cam and intake looked good but did nothing for performance). The 330 ran solid with no problems what so ever. I ran it from the Maumee River to Mienkes West flat out one day, feeling guilty the whole time, but that lo-po motor would only rev to 4600 and never even hurt it (probably a 1/2 hr run).


Oh, on the rod side clearences they were checked and I don't remember the specs but they don't stick out as a problem.