Bearing Problems-BBC
 

Gentlemen,

I am having some issues finding oversize race-grade crank bearings for a Gen 6 502 BBC block. My mains have been bored .020 over and the crank is STD. I can find the stock-style aluminum bearings .020 over but those will not hold up for long. Does anyone know where I can get custom bearings made or what company might manufacture oversize race/heavy duty bearings to fit? I can't be the only one who has run into this.....the rest of the block is cherry and is ready to go.

The engine will be a fuel injected 540. Ported Iron Eagle heads, Bob Madera ground cam. EMI Exhaust. Heavily modified MPI setup.

I appreciate any help or opinions.

Your mains are bored? Are you sure that is correct? I have seen .002 over rod bearings for the housing bore but never on the mains ....especially .020

Yes, Mains are bored .020 over....double checked with bore gauge. I can't believe that this isn't a common way to fix spun mains.

Clevite does make them, but not in a performance bearing. Only 1-4 are .020" over, The thrust stays std.
But... they only make them in .010 and .020 under journal size.

What was the dimension you came up with when you checked them with a bore gauge?

Im not trying to be difficult but you are saying the main housing bore is 2.9570/2.9580 ?

No, but my block is trying to be difficult! :lolhit:

I got the block for cheap (probably the reason) so I can't complain too much....everything comes at a cost I guess. Previous owner took it on trade so didn't know the history.

Yes, that is correct. What is the common way to repair spun mains? Sleeving them? Have heard of that being done before just figured that an over-sized bearing would be easier. There I go thinking again.

You can use shim stock under the bearing

:eek:

why didn't they machine the caps, then align hone the block to standard size?

No clue.....found all of this out after I bought block. Now I need to make it work.

LOL, or spray weld and bore back to size

The saddles were probably hurt beyond that point. Not a good idea to move the crankshaft centerline that much... It becomes more than a .005 or .010 short timing chain can compensate for. The bigger issue with a one piece rear seal block, such as a Gen VI, is that the crankshaft centerline moves up, but the rear seal does not... ie: rear seal leak. Boring the main housing bores oversize has become more commonplace with most engines being one piece rear seal. On a Mark IV block, the seal retaining area is the same dimension as the housing bore... when you cut the cap and hone the bore to std. size, the seal area size and alignment is corrected along with the housing bore.

What kind of block is it? It may not be worth repairing. You can machine the block for a saddle but to do that on all 5 is going to be costly. So you need to really consider is the block worth it?

There is no signs of heat damage along the mains either so if they spun, it wasn't for long. I see no evidence of any kind of major mishap. A friend picked it up for me out of state and had his local shop hot tank, check it out and put in plugs/cam bearings. Everything is great except for these odd sized mains.

Have you measured all five bores to see if they are all .020 oversize? I'm sure you can get away with using a Clevite 1748P. The Clevite P series bearings are a steel back bearing, and are probably fine for what you're doing. Only problem is, as I stated above, is that only 1-4 are over size... and you'd have to grind your mains .010... cheaper than another block.

Rear thrust is .020 over also.......

Masch,
Very very common procedure to save a block with very badly damaged main bores. You can only do so much with an align hone. The big rebuilders do this pretty regularly to save blocks and all of the major bearing manufacturers make bearings for this purpose. Same goes with cam bearings.

Unfortunately I dont know if anyone makes a good race type bearing. If anyone, I would bet on King.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

CI,
I dont think this is the case, but the thrust might be .010 wider. I have done this to several blocks and all five bearings are the same crank journal size.

King alecular makes them:
Main sets with oversize thrusts in .010", .020" and .030" as well as a special .020" oversize outside diameter "line bore" main set for blocks with +.020" oversize housing bore blocks. (write for further details)
Tried to find you a link, you need to probably call them:
http://www.kingbearings.com/bullseye_tolerance.php

Thanks for the info...I guess you learn something new everyday. Ive been in the business over 20 years and have never seen it.

The Clevite MS1748P is only oversize on 1-4. The thrust uses std housing bore... It's kinda goofy that they do it that way... It's got a standard thrust width, but it's not available in std shaft size... only .010 and .020. OP made the comment that his mains were std, that's why I stated he'd have to grind the mains .010.

See page 402, line 108:

http://www.mahle-aftermarket.com/C125790900540AC0/vwContentByUNID/58A5032D3003098AC12579AB00615520/$FILE/EB-10-07.pdf


At any rate, It's not gonna work for him anyway, as all five bores are +.020. Like you guys said, I do believe King makes the set he needs.

Good info, thanks for posting!

I just can't believe that this isn't a common way to fix this problem with oversize bearings. It is the solution for turned cranks, why not for the more expensive to replace part, the mains? .020 is not a whole lot to have to thicken a bearing.......

I did find that King makes a set....but not in their performance series bearings.

MB5274SI it is an Allecular Silicon bearing. Is this strong enough for a 600 hp marine application? King's web catalog sucks by the way.

King MB5274SI is probably what you will have to use. I would not be afraid of using those bearings as long as you are not making outlandish HP. Also, depending on which crankshaft you are using, you might have to put a chamfer on the bearings to clear the radius on the crank.

Boy, that is really strange that Clevite does it that way. Would pretty much mean that the block would have to be align bored and not honed to finish size.

King just responded to my custom bearing request........500 minimum order. Anybody need over-sized bearings?:lolhit:

Going to give Odessa Babbit a call......they claim they can make any bearing.

What is considered OUTLANDISH? Talking under 650 hp here....but heavy throttle handed driver:rolleyes:

Exactly... Doesn't make much sense.

Do they consider that a custom bearing? It's in their catalog.

I know of a couple that have been modified to at least that horsepower level and are using the "normal" King bearings.

I am almost certain that the last couple of 502's that I have worked on had King bearings in them from the factory. They were both "freshen up" deals and did not need the crankshafts reground so I wanted to put the same exact bearings back in them that came out. After a bunch of measuring and comparing, I pretty much came to the conclusion that the oem bearings were King. After looking at bearings for 25 years you sort of get to know which is which, they all have thier tell tail characteristics even without part numbers.

I think that those bearings would work just fine if they are run with the proper clearance etc. Unfortunately for you, the machine work has already been done so you will have to live with whatever clearance you end up with unless . . .

What I would do is get the King bearings but in .010" undersize. Then you can bolt them together and measure them and have the crankshaft reground to give you the clearance you want to run.

Your other choice is to get the King bearings for your standard crank and see what you have, but if it isnt right you will be stuck with those bearings.

Not sure what other choices you really have :(

I have been emailing back and forth all day with King. She told me:

Ron,

We don’t even have this bearing available in the SI material and don’t have any current plans to produce it, but for your information, our SI material is actually the same as our HP material and it has the same strength to withstand high loads, etc. Please let me know if there is anything else I can help you with.

Thanks,

Diana Walters
King Engine Bearings, Inc.
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Phone: (973) 857-0705 Ext. 306
Fax: (973) 857-3228
[email protected]

I also sent her a PDF of her catalog.......getting quite frusterated. Also asked if they made that bearing in any other material.

GF,

Are you talking about the MB7254SI ?

I have found that King's support really is not very good. The best thing to do is try to order the bearing or have a warehouse actually check to see if it is available. I will try to remember and have my PBM warehouse check on it in the morning.

Yes, but it is MB5274SI.......You have little dyslexia there...haha. I tried calling a few king distributors yesterday...nobody had them...supposed to call me back...believe that when I see it.

i think this block will make a good mooring anchor...you got it cheap. once you have custom bearings made it won't be cheap any more. then you hafta consider that you may need to freshen it up in 2 or 3 or 4 years...

Geeze I wasn't even drinking last night :) If I hear anything I will let you know also.

I appreciate the help....Thank You!

Well, no luck here. My warehouse called them and they are not available. My only other thought would be to try calling a couple of the big rebuilders like Jasper, Grooms etc and see if they use them and possibly have a set available.

My last response from King. What constitutes enough demand to make a run of these bearings?

Ron,

I apologize, but we did have these available previously, and if we have enough demand we may produce it again, but at the moment there are no plans to produce it. That is why it has not been removed from our catalog. Unfortunately we do not have anything available right now. Please let me know if there is anything else I can help you with.

Thanks,

Diana Walters
King Engine Bearings, Inc.
Subscribe to our eNewsletter! Click here
Phone: (973) 857-0705 Ext. 306
Fax: (973) 857-3228
[email protected]

Why wouldn't Clevite MS829H20 work? If I understand the issue you need all 5 main bearings .020" undersized, right? H bearings are for nascar.

http://www.summitracing.com/parts/CLE-MS829H20/

That's for a .020 undersize shaft diameter. His shaft is standard, but the bearing housing bores in the block are .020 oversize.