512 bearing problems (long)

Hi all:

I put together a 512 stroker a couple of years ago and have had continuous bearing failures which have me at a loss. Here's the story.
400 block, callies crank, eagle BBC 6.535 rods, 13.5 compression, .700 lift roller cam, milodon pan and swinging pickup with milodon pump cover, melling HV oil pump. Put it together in 2008 and made 4 passes on it and it put number 6 rod out the side of the block. There wasn't much left to look at but 5/6 journal was blackened. After much review, i figured it was an oil leak out of the lifter bores. So i had the crank welded bushed the lifter bores in the replacement block, new rods and pistons and tried it again. By now its 2009. Ran if in the garage for a total of about 20 minutes and the bearings (especially 5/6) look terrible. Main bearings look good enough to use again, although i wont. Lots of scratches and worn down to the copper. Out it comes again. I figured that it was running out of oil at the journal, so I opened up the feed holes to the mains, put restrictors into the cam holes, and added a second feed to oil galley with a braided steel hose (old school, but I am desparate at this point). I replaced the swinging pick up and pan with a static pick up version and changed all the hoses as well as the remote filter. I crack check the crank and see that the small pits coming out, looks like the weld is coming apart, so order up a new crank. Just got it all together again and the ran it for approx 10 minutes (warm up, set valve, timing etc) and the bearings look like the picture. The clearance on the rods was between 0.0015 to 0.002. I had about 60 psi oil pressure at idle hot, about 70 cold.
So far the only part i haven't replaced is the oil pump cover, but it looks fine, and i don't like just changing parts unless i can see a problem. Anyone have any ideas? I am running out of ideas, patience and $.

Thanks!
Tony

I see either dirt, debris or to close on the bearing to crankshaft clearances in the center of that bearing I like more clearances on the bearings to crankshaft than your using, to tight is way worse on a race motor than loose. Try having the crank ground down another .001 and try that, .0025 or looser on all of the bearings, rods and mains (all of my motors end up with .003+ rod and main bearing clearances)

As a rule of thumb you need .001 per inch of journal diameter, PLUS .0005 for added insurance. On the mains you can use this but you need a good alignment of the mains and a straight crank.

thanks for the replies, guys. i was told to tighten up the rods by another builder this time around. They were around 2.5 though before. I suppose I'll loosen them up next time. I had been using plastigage before to measure the clearance, but I used a bore gage this time. I set a micrometer on the rod journal diameter and zeroed the bore gage on it. Then read the clearance directly from the bore gage. I noticed that the bore gage could scratch the bearing (spring too tight) and could conceivably give a clearance greater than actual. Is this what you guys use, or should i check with plasigage and stop fooling around with the bore gage?

I was really shocked to see how quickly the bearings went out (literally 10 minutes idling). I pulled out #2 rod bearing and it looks in decent shape, except for some wear around the top of the bearing.

I am starting to think the mopar is rejecting the bowtie parts!

tony

How much crank end float? , are the rods centred on the pins? , how much rod side clearance?

Wow, that is really bad news. You changed basicly everything but the crank, and I assume when it was welded and ground it was checked for everything. So, I am thinking something else is the cause.

What bearings are you using?

FWIW, in my 511 low deck I use Clevite MS1277HG main bearings (0.0029") [RB mains],
and Clevite CB-743HXK (xtra clearance, coated, 0.0020") [2.200 journals].
I am not saying you need the coated bearings, that is just what I use, and would run looser (0.0025") without coating. I currently have 529 passes on the rod bearings, and 247 on the mains. The rod bearings always looked like new during the inspections, so I keep putting them back in. The mains were OK at the last inspection, but not perfect so I changed them while it was apart.

I would look real close at the oiling system also.
What was the piston to head clearance?

Well, looks like I may have found the problem. While pulling the motor last night I got a face full of gas out of all the rear cylinders when I was taking out the flex plate bolts. Good thing I put out the cigarette!. Pulled the head and found more gas on each of the rear cylinders. I dont' think i noticed before as i turned the motor over before pulling the heads. I had a hard cranking problem that I attributed to a dying battery, but now i am sure it was hydraulicing during cranking. Turns out one of the rear jets fell out of the extention and might have stuck the float, although fuel never came out of the vent. I never took off the float bowl since i don't know when. BTW, end clearance is 0.002 and the side clearance is 0.025 and less. Deck clearance was 0.040 is 0.060 now (different gaskets)

Jim, the bearings I used where CB743HN's. I was going to use the oversized ones this time to get a bit more clearance on the rods.

I really learned a lot on this deal. I even built a small oil pump dyno last winter to check pressure vs flow with various restrictions, measured oil flow with crank at various positions, etc. None of it helped. Should've checked the jets.

Thx for all the replies. I'll post more when I get it back together.

tony

Quote:

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Well, looks like I may have found the problem. While pulling the motor last night I got a face full of gas out of all the rear cylinders when I was taking out the flex plate bolts. Good thing I put out the cigarette!. Pulled the head and found more gas on each of the rear cylinders. I dont' think i noticed before as i turned the motor over before pulling the heads. I had a hard cranking problem that I attributed to a dying battery, but now i am sure it was hydraulicing during cranking. Turns out one of the rear jets fell out of the extention and might have stuck the float, although fuel never came out of the vent. I never took off the float bowl since i don't know when. BTW, end clearance is 0.002 and the side clearance is 0.025 and less. Deck clearance was 0.040 is 0.060 now (different gaskets)

Jim, the bearings I used where CB743HN's. I was going to use the oversized ones this time to get a bit more clearance on the rods.

I really learned a lot on this deal. I even built a small oil pump dyno last winter to check pressure vs flow with various restrictions, measured oil flow with crank at various positions, etc. None of it helped. Should've checked the jets.

Thx for all the replies. I'll post more when I get it back together.

tony

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Dude, I'm really sorry to hear that, check the rods and crankshaft for cracks and being bent now before putting the motor back together Way better to be safe than sorry, no fun being upside down sparking the roof off of the car because something broke sometimes the dammdest things bite us racers