BrazilianZ28Camaro wrote:Have you tested the oil flow to the cam bearings?
Seem there's no adequate oil volume at the bearings...
A bit hard to describe from the image above, but the oil hole is apposite the shadow in that image. Yes, there is some damage there. I'll see if I can post some better pics later.Is the bearing demage at the opposite side of the oil hole??
Have. No obstructions or dirt. Definitely going to check and clean it again. Probably see if I can see anything else with the boroscope we may have missed the previous two times.You should check the oil passages for dirty or clogged.
SilverXJ wrote:No, how is that done?
SilverXJ wrote:Do you know if his two cams were from the same company? His situation does sound like mine.
SilverXJ wrote:I'm hoping someone here can help me out with a problem I have been having.
I've had recent cam bearing failures. Two different block, two different cams. This is a 4.6L Jeep stroker engine. 4.0L block, 258 crank, 4.0L rods, KB pistons, Harland sharp roller rockers. Nothing special.
The first block was fine with a Comp Cam. Had a few thousand miles on it then changed it for an Isky cam and new lifters (with less lift than the Comp). Cam spun when it was installed with little pressure. Main and rod bearing clearances were .0018"-.0020. Cam breakin went fine using Joe Gibbs 50wt break in oil 30 minutes between 2000-2500 rpm, flat tappet hydraulic. Oil pressure started out good then I started noticing the pressure was dropping at idle. Standard volume oil pump, Clevite bearings. Bearing material was pushed out at the bottom and babbit looked like it had been spread about. All the oil holes on the cam bearings lined up with the galleys. No binding in the valve train. Plenty of room on the springs before bind as well as with the retainers to stem seals in rocker pivot. Cam tunnel checked out straight and true.
Taken from the bottom of the block.
New block ,new parts, crank turned. New Clay Smith cam, new lifters, bearing, oil pump, etc. Used Durabond cam bearings this time around. Same thing. Oil pressure started out good then dropping to less than 20 PSI at a hot idle. Used 30wt Brad Penn break in oil. Main and rod bearings were .0018"-.0020" again. Cam spun fine, and bearings lined up with the galley holes. Looks like #2 is worse, then #3, then #1 and #4 being the best.
My machinist thinks oil volume is being bled off through the push rods (.080" hole in push rod, nearly a straight shot to open air). However, Other people have used this combo with out this issue. As well as initial oil pressure was good. Possible, but I don't know. I left out a lot of details trying to keep this short. Any ideas would be greatly appreciated. Or let me know if you want more details.