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Thread: 1.6 Xflow Max Bore Wear

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    1.6 Xflow Max Bore Wear

    I'm putting a Solex on a 1.6 Kent with low boost, and I am fitting custom forged pistons for the build. This car will be for the street. The engine is stripped and I'm taking measurements to get the pistons ordered. I measured the bores as follows to get a feel for the starting condition:
    • I took an out-of-round measurement for each cylinder by measuring parallel to the crankshaft and perpendicular to the crank at the top of the worn-in area of the bore (beneath the ridge). Subtracting these two numbers, the max value obtained is 0.0019 inch (google says that's 0.04826mm).
    • I measured bore taper at top, middle (taken just for reference), and bottom for each cylinder (I should note I eyeball-ed where top, middle, and bottom was) parallel to the crankshaft. Subtracting top and bottom values I obtained a max taper of 0.0010 inch (0.0254mm). For fun I also measured the taper perpendicular to the crank, also obtained a max of 0.0010 inch.
    These measurements were performed without honing. If I remember correctly, the book "Engine Builder's Handbook" claims taper should be less than 0.0030 inch for a reasonable rebuild (though acknowledges if its not perfect it should be re-bored). The book does not contain guidance on out of round. Also, the book was not written for boosted applications. My question is, of course, are these reasonable measurements to continue with just a hone? I'm planning on using the ball flex-hone and doing it myself unless it is highly recommended otherwise. Possible a proper honing device would straighten the bores up some and be worth the while? Worse case, I can take it in to a shop for the whole 9 yards.

    I will be sure to re-measure everything after the hone and use those numbers for the piston order form.

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    1.6 Xflow Max Bore Wear

    Would you not be better ordering Pistons in an off the shelf size for xf weather std bore or overbore ? Otherwise they will only ever fit your ( worn) engine ?


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    Re: 1.6 Xflow Max Bore Wear

    Would love to, but the only forged pistons I can find are the Accralite or similar, which have a 12:1 compression ratio.... too high for turbo charging. They are also more expensive after shipping then the custom built JE Pistons would be, not even considering the machining costs of having them cut down to lower CR. If re-bore is the way I go, I will probably target one of the off-the-shelf overbore sizes, just to keep things nice and easy. Still would go with the custom JE's.

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    1.6 Xflow Max Bore Wear

    Yes sorry I wasn't clear , stick with customs for reasons as you say but order in a std ie off shelf bore size so they will fit another block should it be required or rings needed etc


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    Re: 1.6 Xflow Max Bore Wear

    Am I missing something - your two different measurements were 0.002 and 0.001" and the guide says should be less than 0.003".......which yours is?

    I'm guessing its more of a 'glaze bust' rather than a mechanical hone which therefore shouldn't affect bore size significantly. I'm thinking that as long as the actual
    bore diameter isn't above o/a tolerance and correct piston to bore can be obtained then a glaze bust is all that is required - unless the top ring is higher which would
    conflict with wear line but as a turbo type piston should wear its top ring further down from the crown. it shouldn't be an issue!

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    Re: 1.6 Xflow Max Bore Wear

    bearing in mind that forged pistons run bigger clearances and that aftermarket rings tend to be in "round" sizes would it not be best simply to have the pistons in an oversize and have you block properly bored/honed to suit? then as alladin said, if you in futire have an issue with teh block you can fit them into another block, the chances of finding a second std size block which doesnt need boring is slim

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    Re: 1.6 Xflow Max Bore Wear

    Katana: my taper is within the specs suggested in the book, but the book isn't for turbo'd engines... wasn't sure if there is less tolerance for taper due to the higher operating pressure? I guess boost pressure is negligible compared to the actual combustion event, so maybe I'm over thinking it. My other problem is the book doesn't give an out-of-round spec, not sure why. I'm going to be running less compression than stock, so JE will probably make the piston with lower compression height so the ring height shouldn't be an issue, like you said.

    Graham: I didn't think about available ring sizes, good call. Xflows here in the states are not nearly as common as they seem to be in Europe, if this engine goes sour it will probably mean engine swap rather than new block.

    I know it's better to go with the fresh bore, but I'm trying to avoid going down the "well I might as well do this too" rabbit hole. I already had to force myself out of considering the roller rockers from Burton. This is supposed to be a cheap project, but I do want to do it right enough to last a decent while. Sounds like things would be a lot simpler with just doing it right, with the bore-job though. Then I won't have to worry about. I'll spec the pistons to be in a readily available over-bore size with available rings, then have the bore job done upon their arrival to the clearance spec that I assume will be provided by JE Pistons.

    Thanks for the input everyone.

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    Re: 1.6 Xflow Max Bore Wear

    Quote Originally Posted by blastronaught View Post
    Would love to, but the only forged pistons I can find are the Accralite or similar, which have a 12:1 compression ratio.... too high for turbo charging. They are also more expensive after shipping then the custom built JE Pistons would be, not even considering the machining costs of having them cut down to lower CR. If re-bore is the way I go, I will probably target one of the off-the-shelf overbore sizes, just to keep things nice and easy. Still would go with the custom JE's.
    i used unfinished crown twin cam pistons from accralite as they had the thickest crown available. you can juggle the comp ratio with different thickness cometic gaskets . mines running 1.8 bar at the mo.

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