4.3 Merc oil leak on top of intake

[wire2]

Re: 4.3 Merc oil leak on top of intake

Yes, the cylinder walls and cam lobes get oiled by the counter weights slinging oil, but it's not from running in oil in the pan. It's slinging oil that's draining back from the top of the motor.

Ok, that may be the case, but I'm dubious that it's coming from the top of the engine.
The heads get oil pumped up through the lifters, push rods and spit out by the rockers. It drains through small openings in the head casting, usually front & rear. The drain holes have to line up with a hole in the head gasket, and then drains down a return hole in the block. There's probably 2 drain holes on each side in a SBC, front & rear, and the oil will tend to trickle down the casting, not onto the crank.

I'm thinking it's more likely that oil is being thrown from the crank con rod journals, which are under pressure. All 8 con rods are directly in line with a cylinder, so lots of small drops being flung up at TDC of each piston.
Anyone?

 

[coheej]

Re: 4.3 Merc oil leak on top of intake

Ok, that may be the case, but I'm dubious that it's coming from the top of the engine.
The heads get oil pumped up through the lifters, push rods and spit out by the rockers. It drains through small openings in the head casting, usually front & rear. The drain holes have to line up with a hole in the head gasket, and then drains down a return hole in the block. There's probably 2 drain holes on each side in a SBC, front & rear, and the oil will tend to trickle down the casting, not onto the crank.

I'm thinking it's more likely that oil is being thrown from the crank con rod journals, which are under pressure. All 8 con rods are directly in line with a cylinder, so lots of small drops being flung up at TDC of each piston.
Anyone?

If you take an oil pan and fill it with the correct amount of oil minus what's in the filter, it would not come up out of the sump area. Also, don't forget the rods are throwing all of the oil coming through the rod bearings. When the engine is running, there is a significant amount of oil in circulation through out the engine. There may only be 3 quarts in the pan at that time.

 

[John_S]

Re: 4.3 Merc oil leak on top of intake

Lots of info posted here: http://forum.grumpysperformance.com/viewtopic.php?f=54&t=615

About half way down, is a routing diagram or two.

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

Lost compression in #6. Need to start a new thread.

 

[Aloysius]

Re: 4.3 Merc oil leak on top of intake

Cylinders oil from the rod journals throwing off oil. Bearing clearances that are too wide, or too much side gap on the rods will throw excessive oil on the cylinders. Counterweights hitting the oil have nothing to do with lubricating the cylinders..if that were true, dry sump motors wouldn't work.

rod bearings are semi-pressurized. Centrifugal force forces the oil to the rods from the main journal..they oil when the holes in the crank line up with the hole drilled to the rod bearing. Grooved mains help supply oil to the rods in extreme use.

Cams are lubed by oil returning through holes in the valley, and oil slinging off the rod journals.

some Chebby marine engines use a windage tray to separate the oil from the crankshaft.

I was wondering if there was excessive blowby, which you've now confirmed. burned a piston I bet.

 

[John_S]

Re: 4.3 Merc oil leak on top of intake

Cams are lubed by oil returning through holes in the valley, and oil slinging off the rod journals.
.

Cam bearings have direct oil pressure feed like the crankshaft bearings.

The cam lobes are lubricated via the lifter bore. The lifters only take on the oil when the hole in the side of the lifter aligns with the oil passage. When the holes are not aligned, the oil lubricates the lifter bore and runs down the lifter onto the cam lobes.

 

[Aloysius]

Re: 4.3 Merc oil leak on top of intake

Hopefully it runs down the lifter..they're pretty tight (less than 0.001"), because the oil has to be forced up the pushrods to lube/cool the head. The cam bearings ARE pressure lubed, as they're in the oil galley that feeds the lifters...that feed the pushrods...that lube the rockers. The lifters are off center of the cam lobe, so they spin in their bore. roller lifters are different, and don't need as much oiling, since the tremendous shear load is removed.

There have been instances of cam lobe failure (flat tappet)on sustained low rpm engines from lack of oil. source was traced to not enough oil being throw off the crank throws.

 

[wire2]

Re: 4.3 Merc oil leak on top of intake

.... the oil has to be forced up the pushrods to lube/cool the head. .....

I have to question the cooling abilities of engine oil.
My car (Charger SRT) has a bunch of extra features in the dash displays, one of them being oil temperature.
During normal cruising speeds (2200 rpm/70 mph) the oil reads 105? C (221? F) while the coolant temp is 170? F.
Under "spirited" driving, the oil temp goes even higher but coolant remains at 170.
It would appear as though the oil is being cooled by the head, not the reverse.

 

[imported_TheMan]

Re: 4.3 Merc oil leak on top of intake

Sounds like a good time to add an engine oil cooler.

Isn't oil ideally supposed to be 180 - 200F?

 

[coheej]

Re: 4.3 Merc oil leak on top of intake

The oil is taking heat away from the bearings.

 

[Aloysius]

Re: 4.3 Merc oil leak on top of intake

Oil temperature should be over 212 degrees..220-240 or so is fine.

The coolant temperature and the ACTUAL head temperature are quite different. The coolant passes through so fast it doesn't pick up ALL the heat in the head. That's why "heat soak" happens if you shut an engine off immediately after running it hard.

Most engine heat is produced in the heads, due to the tremendous heat input from combustion. Bearings produce very little heat in relation to the head, since bearing heat is ONLY produced by friction. The only cooling for bearings is from the oil.

 

[Evinrude Boater]

Re: 4.3 Merc oil leak on top of intake

I was wondering if there was excessive blowby, which you've now confirmed. burned a piston I bet.

Scored, corroded and gouged cylinder wall. I imagine the piston and rings are damaged too. If she ran good as a lame engine I can't wait to experience a fresh 6 cylinder!!!
Any thoughts on the cause of such damage?

 

[Aloysius]

Re: 4.3 Merc oil leak on top of intake

Looks like detonation, from the aluminum buildup on the top of the cylinder. Probably damaged the rod from the shock load also. NOT oil related.