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Thread: What crankshaft is in ST170

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    Spanner Monkey

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    What crankshaft is in ST170

    Hi guys. I am going to build ST170 Zetec (but branded Duratec) engine for my MK2 Escort. Have an engine here, but still complete. Let me ask you what crank is there. Steel or cast? Somewhere is written steel (some forums) somewhere cast iron. Conrods are steel? Thanks for answers...

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    Re: What crankshaft is in ST170

    rods might be steel, there is steel and steel, could be cast forged or billet!

    cast steel is nothing like as good as billet steel as used in proper race rods

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    Re: What crankshaft is in ST170

    my idea is to use eagle rods (H), the main problem is the crank. if to keep original or change it for some other. want to go up to about 220/230bhp and 8.200 rpm

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    Re: What crankshaft is in ST170

    ive got an st170 crank here, quite nice looking, rolled fillets on the journals, dont know what its made of but i can tell you its cast not forged

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    Re: What crankshaft is in ST170

    i am thinking about this one: http://www.burtonpower.com/farndon-e...c-e-fz324.html
    i hope this one is forged steel (or steel only?). to save some money for other parts i prefer to stay with std crank, just i´m not sure, if it will handle rpm and 11,5:1 ratio.
    anyway...do you have some info where to find good set for dry sump?

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    Re: What crankshaft is in ST170

    Why worry about whether the ST 170 engines are cast or steel. They are a solid robust tried and tested production engine so why not just use them as std as they'll take unlimited amounts of abuse. Engines can be picked up for a few hundred pounds so it's not the end of the world if one fails.

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    Re: What crankshaft is in ST170

    its not compression which breaks cranks it fatigue and rpm, the more rpm the quicker it will fatigue, even running at just 2000rpm will break one eventually, might take 200 years but sooner or later it will break.

    i cant see you having a problem with a standard crank, certainly not at that power level, you can coax 200 bhp out of an engine with std internals!

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    Spanner Monkey

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    Re: What crankshaft is in ST170

    well...not the end of the world, but maybe the end of season for me. better to spend more once for better parts, than 3x a few hundred for std parts:-)

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    Re: What crankshaft is in ST170

    ok, thanks for your opinion!

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    Re: What crankshaft is in ST170

    What makes you think every crank will fail at somepoint Graham? any rotating shaft will only fail if the cyclic stresses applied exceed its fatigue limit, commonly known as endurance or fatigue limit, provided a crank isnt put beyond its yield strength, it should never fail. 2000rpm should never put a crank past its fatigue limit.

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    Re: What crankshaft is in ST170

    Quote Originally Posted by Erikmex View Post
    What makes you think every crank will fail at somepoint Graham? any rotating shaft will only fail if the cyclic stresses applied exceed its fatigue limit, commonly known as endurance or fatigue limit, provided a crank isnt put beyond its yield strength, it should never fail. 2000rpm should never put a crank past its fatigue limit.
    i did say it might take 200 years! that said we have seen a few broken cranks in diesel freelanders, they certainly weren't being revved passed the fatigue limit

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    Re: What crankshaft is in ST170

    Hi. The st crank is stronger than the std blacktop. The weakness is the oils pump, the crank flexes over 8krpm, which in turn can pinch the oil pump gear, causing it to destruct. They respond well to head work, but std pistons start to give up when using raised compression and high rpm. Rods are shot peened and a fracture cap, better than std stuff, but not steel rods as you'd use .

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