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Thread: Xflow Oversized main bearing housing problem

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    Xflow Oversized main bearing housing problem

    Hi. Been lurking here for a few years but only just registered as I could do with some help.

    I recently purchased a 2nd hand but excellent condition 711m block without main caps. On getting it home I have measured the block part of the main cap housing to find it oversized. The main caps I have are standard size.
    How can I overcome this issue?
    Can I use oversize bearings for the block half of the mains and standard for the caps?
    Is it possible to have just the caps machined to match the +.15 of the block?

    Thank you

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    Re: Xflow Oversized main bearing housing problem

    Unfortunately the caps are matched to the block. You may be able to get them line bored for your oversize block but you need to know if you can obtain oversize bearings for your purpose. It may be alot easier to obtain another block which someone may have already done.

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    Re: Xflow Oversized main bearing housing problem

    If the block is already oversize one would assume oversize OD bearings are available? So line boring the 'underside' std. caps should be an option - even if it is only one sided! An 'out of the box' idea would be metal spray the oversize journals back to undersize then line bore to std to match the caps? Multitude cat skinning methods!

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    Re: Xflow Oversized main bearing housing problem

    Bearings are available from burtons at £96 a set for oversize housing (cheaper supplier suggestions welcome)

    I have had a price for line boring at £350-£400!! Seems excessive?
    Can't guarantee either that only the caps will loose material and none extra from the block.

    Might have to source a new block because at the moment it's a £200 door stop. Add the machining and it could be £600!

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    Re: Xflow Oversized main bearing housing problem

    If I use oversize housing bearings on the block part of housing and standard on cap side, what problems would this cause? Oil lubrication issue at back of bearing?
    The journal side of the bearing would be the same diameter all the way would it not? Just a 0.15 step on the bottom half of housing bearings. Obviously get same manufacturer/brand and 2 sets of bearings would come in at £150

    If that makes sense to anyone

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    Re: Xflow Oversized main bearing housing problem

    If you are into it for £200 then stepped size bearings is a £50 saving if it works - got to be worth a punt? The line boring quote sounds spendy but they maybe quoting for additional lathe work to bring the caps out to within the line boring tool tolerances?

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    Re: Xflow Oversized main bearing housing problem

    As Forest Rallying said, main bearing caps are matched (line bored) to the block. So if you have other main caps then these are in 99.99% of all cases not suitable as is to your block. Because the line which these were bored/matched on will not be the same. Even a very very tiny amount "off-line" would mean the bearing gaps are gone or are too wide.
    Even if you had the matched (unbored) main caps then you would need to have it line-bored because of the same reason (axis line-bore different).

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    Re: Xflow Oversized main bearing housing problem

    Thank you for your responses.
    i have spoken a machine shop who have a block with matching caps that they are going to have acid cleaned, new cam bearings, bore to my 83.73mm pistons and check crank for £400.

    I might do a build thread when that is done so the knowledgable people on here can point out any mistakes if I'm going to make any. Although i would like someone to build the complete engine for me, I can't afford to keep throwing silly money at it.
    I'm not a mechanic but I should be capable of putting a xflow together with a little help

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    Re: Xflow Oversized main bearing housing problem

    The line boring process is expensive because it's the setting up of the tooling that's so time consuming, an engineer that I know waits until he has a batch of blocks to do and that way he says it's so much easier and costs a little less money for the customer.

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