Cam Failure

[Muad'Dib]

FrankZ... i edited your post removing the attachments, and posting the pictures properly that you attached.

You may benefit by reading this thread:

viewtopic.php?f=19&t=112

Thanks.

[John]

You guys took a potty break while I was away....

Oiling for this motor is ah... Mopar says it best here in Mopar Jeep Motors 3rd Edition The last paragraph says a lot. The pump is mounted at the underside of the block opposite the No. 4 main bearing. The pump draws oil through the screen and inlet tube from the front sump at the rear of the oil pan. The oil is driven through the drive and idler gears and pump body, then forced through the outlet to the block. An oil galley in the block channels the oil to the inlet side of the full flow oil filter. After passing through the filter element, the oil passes from the center outlet of the filter through an oil galley that channels the oil up to the main galley which extends the entire length of the block. The oiling system has a capacity of 5.7L (6 quarts). Galleys extend downward from the main oil gallery to the upper shell of each main bearing. The crankshaft is drilled internally to pass oil from the main bearing journals (except No. 4 main bearing journal) to the connecting rod journals.Each connecting rod bearing cap has a small squirt hole. Oil passes through the squirt hole and is thrown off as the rod rotates. This oil throw off lubricates the camshaft lobes, camshaft positiom sensor drive gear, cylinder walls, and piston pins.The hydraulic valve tappets receive oil directly from the main oil galley. Oil is provided to the camshaft bearings through galleys. The front camshaft bearing journal passes oil through the camshaft sprocket to the timing chain. Oil drains back to the oil pan under No. 1 main bearing cap.The oil supply for the rocker arms and bridged pivot assemblies is provided by the hydraulic valve tappets which pass oil through hollow pushrods to a hole in the corresponding rocker arm. Oil from the rocker arm lubricates the valve train components and then passes down through the pushrod guide holes in the cylinder head, past the valve tappet area, and returns to the oil pan.
The stock lubrication system will be adequate for normal passenger car operation. However, in any case where DiamlerChrysler engines are subjected to unusually high crankshaft rotational speeds (over 6,000rpm), acceleration, deceleration, or cornering loads, special precautions must be taken with the engines oiling system. Not only must an engine's oiling system be modified for adequate lubrication, but it must also be modified to achieve optimum engine power output.

Is that better than the thigh bone is connected to the....
John

[oletshot]

A little more detailed than my description.

[oletshot]

When rods are reconditioned they remove material from the cap and then remachine a new hole for the bearing. I wonder if the squirt hole is being removed or made smaller when reconditioning the rod.

FrankZ, I should have been more clear with my con rod lubing the cam. I realized how the cam bearings get their oil, I was referring to the cam lobes and their lubrication at idle. Above idle there is oil being thrown all over the crankcase, thus the 2000rpm breakin to make sure the cam gets plenty of oil splashed on it.

[John]

A little more detailed than my description.

The one during break? LOL
John

[dwg86]

Do the new rod bearings have a knotch in them that would let the oil out? I know there have been some newer bearings being made for the amc v8's that don't have the knotch in them. Some are grinding a knotch in the bearings before they install them.
As for reconditioning the rods...only a couple thousands is taken off, not enough to effect the hole.

[Flash]

Thanks John, that's the way i thought it oiled.......but just wasn't sure.

Frank, i now your getting a lot of guessing thrown at ya, but we all would like to find the real answer or working solution to the problem as well. Your the best test pilot we've got!!!!!

I would be real interesting to see if there was a difference in size of the oil lube hole, in the rods between #5 or #6 compared to the rest of the rods.
Do you have any finger Drill bits?(actually, they may be to small any way, but a drill bit would make for a good comparison between rods) to us as a gauge?

as dwg86 has said, they only take a fue Thousand's off of it.............But could one rod have been recondition before...Or even more then that.........then you have factory machining tolerances that my have sent that rod out on the small side to begin with.............

If you take a look at the two halves of the rod bearing, there is a notch or groove on one end of the bearing shell and a half moon circle that mated with the other or upper shell creating the hole that allows oil to exit the rod thru the half moon holes in the rod cap/rod...........When you check the diameter of these holes, make sure the rod cap nuts/bolts are torqued to spec before you check the size of the lube hole.

Thanks
Flash

[oletshot]

It seems to me that the rod squirt hole was actually on the rod itself not the cap, I remember a V groove going around the rod bolt then out the side. Probably makes no difference to the theory though, as I'm sure they press out the bolts and remove material from the rod also during reconditioning.

Flash, my guess would be that the extra stroke wouldn't have anything to do with it. The 258 uses the same oiling system the 4.0 uses

[John]

It seems to me that the rod squirt hole was actually on the rod itself not the cap, I remember a V groove going around the rod bolt then out the side. Probably makes no difference to the theory though, as I'm sure they press out the bolts and remove material from the rod also during reconditioning.

Flash, my guess would be that the extra stroke wouldn't have anything to do with it. The 258 uses the same oiling system the 4.0 uses

Your memory is pretty good, just looked at a unconditioned long and short rod. The bearing cap furnishes one side of a triangle shaped galley running from the rod bearing opening flowing around the rod bolt and out a triangle shaped galley to the crankcase to ah spray anything it passes. Our cam is really relying on splash lubrication for the lobes, really bad to idle these. Also think Oletshot is correct with the thought that changing the stroke wouldn't be change its performance in real world terms.We still pass the camshaft twice for each revolution, we do change the timing of the event somewhat (rod speed etc). A properly reconditioned rod really does not remove that much material from this area prior to re cutting for the bearing.
John

[FrankZ]

I talked to the shop this morning about the oil hole. He told be that my robds took a minimal amountof clean-up so I don't think the oil hole is an issue. No parts yet so nothing new here.

[4point6]

Here is an interesting article from Hod Rod on flat tappet cam problems. Sounds like Jeeps aren't the only ones with cam failures.

http://www.hotrod.com/techarticles/engi ... index.html

There are some suggested oils to use there also with higher zinc content, Rotella 15W40 included.

[cherokee]

What about the possibility of a reversed rod cap? The connecting rod section of the Jeep motor book mentions lubrication of the opposite cylinder bank (obviously information meant for a v8 despite being in the 4.0 section). Is it possible that in the case of the 4.0 a reversed cap squirts oil away from the camshaft instead of towards it?

[FrankZ]

Nope, caps were all on correctly.

[Flash]

Here is an interesting article from Hod Rod on flat tappet cam problems. Sounds like Jeeps aren't the only ones with cam failures.

http://www.hotrod.com/techarticles/engi ... index.html

There are some suggested oils to use there also with higher zinc content, Rotella 15W40 included.

Frank, on the 2nt page of the link above^^^......It said this

"Rabotnick mentions yet another possible contributing factor: "Many daily-use or street/strip hot rod engines are built up from35-to-40-year-old engine blocks. The average builder never checks the lifter-body-to-lifter-bore clearance. It may have doubled. Pro guys bushthe lifter bores, but most homebuilders just dust the bore with a brake-hone to make the bore smoother and remove varnish. If there's morethan 0.001-0.0015-inch clearance, you could be in trouble." But Comp'sGodbold counters, "We see the same type [of] problems whether it's abrand-new CNC-machined Dart block or a junkyard block."
Just another thought and place to check!!!!"


A question to those that have had 2, or more cam fail. In the same block......was it the same lobe??????


Flash

[4point6]

So we know of a lot of camshaft failure scenarios - anyone have any stroker builds that have some miles on them, with no problems? If so what is the build (cam, oil pump type, piston/rod combo, valve spring combo, CR, quench, block/head work done, oil used or additive added, etc.), how many miles, how it was broken in, how the engine was used (light duty DD vs dedicated rock crawler vs high rev), etc. The more data the better. Maybe this will help eliminate some ??'s.