Bearing Questions.

So, my refresh made a total of 6 passes before it kicked a rod. Now, from my own post-mortem, it appears that a crack in #3 cyl wall let in some water. The piston encountered said water at about 6500, and took the wrist pin right out. I'm down two rods, a piston, and a pan. Needs a sleeve, obviously. The cam has some nicks, and some marks you can just barely feel with a fingernail. IIRC, I can send it back to Comp for a repair. If not, new it is. The pistons, luckily are still current in the KB/Icon catalog, as are the Eagle rods. #3/4 rod journal is not pretty.
What is of deeper concern is the state of the bearings. I put new mains and rod bearings in, and several are not pretty. #5 and #6 rod bearings are showing copper, and the mains are just plain rough. I assembled using liberal amounts of Lubriplate, as I have in the past. The engine was very well pre-oiled, and oil pressure was good on initial fire-up. Even if I hadn't cracked a cylinder, this thing was on borrowed time. It's worth noting that the two actual good passes I got, out of six, it ran almost a full tenth quicker than it had been, with a 1.52 60' launching it with a solid 700-800 more on the converter than it has ever liked in the past. And .050 less valve lift (Thank you PRW rockers.) What might I have done to hurt those bearings so quickly? I'll try and post up some pics later.

Why did you refresh the engine before i?

What engine. What bearing clearances? I’m not a fan of any paste type assembly lube. If it’s a small block and you are running solid lifters you need to tube the passenger side oil gallery and plug off the drivers side at the number 1 main bearing.

You SHOULD be using full groove mains and a high volume pump. Your bearing clearance should be tight enough (.0020-.0022 on the rods and .0023-.0025 on the mains) so you can run a good, not off the shelf 5w30 or ow20 synthetic oil. Just my .02

It's a 360, solid roller. The reason I did the refresh was that I felt it was getting tired. I'm using a Comp lifter that doesn't require tubing the oil galley, and has worked well for the past several years. The old bearings actually looked really good, that's what has me scratching my head.

I’m not sure what lifter that is, but on any solid lifter application the block should be tubed or the lifter bores bushed. The leaks around the lifters are incredible.

Parts don't fail for no reason, even in racing.
Now is the time for you to figure out what EXACTLY caused the failure.
Trying to do a accurate biopsy on broken parts ain't easy but it is doable
good luck, let us know what you end up finding and thinking

Cab- Good point. At the initial start up, the oil pressure was exactly as it should be- quick jump to 60 psi at idle cold, dropping off to 50 psi at idle hot, with the brief delay at shut-off before it falls to 0. After a few passes, I noticed, but it didn't fully register with me, that the oil pressure was swinging quite dramatically when I was trying to sort out the carb/idle issue. The pressure would drop to almost zero whenever the motor fell off the idle. When that sunk in, the internals had already been externalized. My first thought was that a rod bolt had let go. The rod bolt that did fail was collateral damage. The cylinder wall crack was the biggie. I'll try and post a pic of the top of the piston. It was definitely hydrauliced, with absolutely no indications that piston and head made contact. I do have this to add- When I put the roller in, the cam that was shipped to me was for a Magnum, and had no rocker oil grooves. That was treated as no biggie, as I have friends with lathes. However, there was a small discrepancy between groove sizes, and the passenger side rockers have had a bit of an oiling issue. When I had the motor apart this time, I had my friend cut that one groove .010" deeper and about .015" wider. I no longer have a passenger side rocker oiling problem (cue the "Well duh, of course it ain't NOW" comments) I have a hard time believing that modest change up would have resulted in the bearing damage I'm seeing. 'Tis a mystery, wot?

another question: what bore size did you run, and did the damage come from weak bore or corrosion?

Michael

Was there water in the oil prior to the hydraulic issue?
Doug

It was running fine before the refresh? It doesn't make sense that it just cracked after you rebuilt it.

No water in the oil prior to the rapid disassembly. In the end, it was running fine before I tore it down, but it was getting tired. The oil pressure was getting a little "soft"- 40-45 psi at hot idle vs 50, a little more blue smoke on hot starts, that sort of thing. This is a .040 over motor, 1973 block. I know cracked cylinder walls are a bit odd for 360's, but the shape of the deformation of the piston top is what's leading me to think cracked wall being the cause. There's definitely a crack now.

Unless the crack was large enough to see through, I would consider it secondary. I had a 2" long crack in #5 that was misdiagnosed as bad head gasket causing overheating. The cylinder wall was rusted/pitted from it being that way so long. I would push out a gallon of water, but it still finished Rocky Mountain Race Week with frequent refills.

Think about it. Your chambers are about 80 CC. 30cc = 1oz. Per the calculators, -30cc's would take my combo from 9.5:1 to 12.5:1. -60cc is 18.4:1. -90cc (3 oz!!!) is 36:1 You would need about 2.5-3 oz. to get into hydraulic lock. Is the crack bad enough to be passing 2-3 oz. of water each cycle?

Did you measure your oil clearances when you installed the new bearings?

#2 and #4 cam journals are each fed from a single drilling that intersects with the main bearing drillings if I recall correctly on a small block.
Grooving the cam journal without installing a restriction to the rocker shafts will reduce oil to the bearings. The bigger the groove, the easier it is for oil to escape the bearings.

The crack is just small, but definitely there. My assumption was that a small crack could let in enough water to kill it. So, most likely rod bolt was the rod-killer. And no, I did not actually check all my clearances. We just bought new bearings based on the part #'s of the existing ones. All the rod and main journals were pristine, with a couple of the bearings showing signs of stress. No grooving, just some copper showing in a few spots.

With only 6 passes before it let go, I would look closer at your first thought. Can you post pictures of the rods, rod caps, bolts.?
Were all the rod bolts still screwed into the rod? i.e. did one come loose.

Hmmm. On the rod that exited the program, one of the bolts had backed out. It's sitting in the bottom of the pan. I never gave that fact much thought.

Finally got a chance to take some more pics. The mains, plus some rod bearings and a pic of the damage to [img]http://[/img] the piston.

More.

Couple more.

Last ones. The pair of rod bearings is the rod that came apart. The one with all the copper is one that didn't fail. Yet.