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K-Series Main Bearing


mahatma

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I'm trying to get some new main bearings for my engine re-build but the code that is supposed to be stamped on the bearing ladder is no longer there *eek*

 

The code on the crank is fine but how can I go about determining which bearings I need to order ? *confused* The engine is still in bits at the moment, so I have the crank, block and bearing ladder all separate.

 

Thanks

 

Andy

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Technically incorrect, but pragmatically often acceptable answer is simply to fit mid-grade bearings. The grades are in steps of approximately .0002", but I've seen more than one K-series with the main bearing housings .003" out of round. Worrying about a grade that is fifteen times smaller than an inaccuracy in the system has always struck me as being a little pointless.

 

I should point out that we would correct such a main housing, but it is not uncommon after the engine has run for a bit.

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Technically incorrect, but pragmatically often acceptable answer is simply to fit mid-grade bearings. The grades are in steps of approximately .0002", but I've seen more than one K-series with the main bearing housings .003" out of round. Worrying about a grade that is fifteen times smaller than an inaccuracy in the system has always struck me as being a little pointless.

 

I should point out that we would correct such a main housing, but it is not uncommon after the engine has run for a bit.

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Thanks Roger.

 

I'm not sure if I understand right, but are you saying that; given the overall engineering tolerances in the engine, using the middle grade bearings is unlikely to give me any problems ... or should I take the crank, block and bearing ladder to an engineering shop and get it checked for roundness and then get a new set of bearings ?

 

I'm not even sure where I would take it, if the engineering shop route is an option, can you recommend somewhere ?

 

Regards,

 

Andy

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It would be a good idea to have your main housings measured, but you must fit the cylinder head too with a K-series before this is done. In the unlikely event that the housings are badly out of round they should be corrected. Scholar can do this, but it is normally unecessary.

 

In most cases, you will probably be OK just to fit mid-grade bearings. I must however point out that this has to be your decison and your responsibility because I haven't seen the engine.

 

 

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Roger, I understand the risks that you are suggesting ... but I absolutely appreciate the advice.

 

I still have the bearings that I removed, separated out in pairs 1 to 5. On closer inspection, I noticed some very small markings on the back side of them - I'd have to get a lens to read them properly but they appear to be numbers. Is there any way that I can collect these markings and use them to specify the new bearings ? or are they just batch number etc ?

 

Also, does anyone know if the bearings are matched pairs; i.e. are the pair for No.1 journal going to be the same size or could they be different top and bottom ?

 

 

Kind regards

 

Andy

 

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The main bearings are not in matched pairs. You have to buy each half as an individual item. The halfs that you require depend on the combination of codes of the crank and block. With the thicker half (where there is a difference) being fitted in the ladder (not the block). The half shells are colour coded (green - thin, blue - inter, red - thick). I have just rebuilt my bottom end and it required red and blue for no. 1 and all blues for the remainder. Also note that you must specify whether the shell half is grooved or plain as well. CHECK CHECK and CHECK again prior to ordering and check again as you fit them.

 

Best of Luck.

 

Colin

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Thanks guys ... this does sound like the sensible option, but is the manufacturing process the same for the R500 cranks and are the journals the same size ?

 

I guess what I'm asking is, are the manufacturing tolerances much more stringent on the R500 crank, block and bearing ladder enabling Minister to only spec one bearing size *confused*

 

Thanks

 

Andy

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OK, could someone just confirm that a full set of mid-grade main bearing means that they are all BLUE - block side and bearing ladder side? I just want to make sure that I get the right ones. With the 3 middle bearing ladder shells being grooved.

 

Thanks

 

Andy

 

 

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