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Thread: Pinto stroker for rallycross

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    Bodger Frits's Avatar

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    Pinto stroker for rallycross

    Hi there,

    I need some advice of the professionals for my new rallycross engine build.😃

    I can get my hands on a yb 86mm stroker Crank. Further I already have a set of stock yb rods.

    The question is, would this combo fit with some 93mm pistons with 38mm compression height, machined down a little? I have my concerns about the Rod ratio, as this would only be 1.49. This engine would only drive competition, but we are on a budget.

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    Re: Pinto stroker for rallycross

    rod ratio will be ok, people get hung up on it, but its been done many times before. your 38mm pistons is that the ones with the really thick crowns?

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    Bodger Frits's Avatar

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    Graham, thanks for the answer. So you think a low Rod ratio would not be that big problem? I calculated, the Piston comp height should be around 35.5mm. I Hope the 38mm ch yb Piston has enough meet to machine down by approx 2.5 to 3mm...

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    Re: Pinto stroker for rallycross

    The very early development Millington Diamond Engines had YB rods with an 84 mm stroke billet crank, so 86 mm should n't be a problem for you. I would check with the piston manufacturer the thickness of the crowns before starting any machining work.

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    Re: Pinto stroker for rallycross

    Quote Originally Posted by Frits View Post
    Graham, thanks for the answer. So you think a low Rod ratio would not be that big problem? I calculated, the Piston comp height should be around 35.5mm. I Hope the 38mm ch yb Piston has enough meet to machine down by approx 2.5 to 3mm...
    did you buy slightly damaged stock clearance ones burton had? in which case you can machine massive amounts off the crowns, in fact you have to because they weigh an absolute ton!

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    Graham, i did not yet bought pistons. Do burton have those pistons?

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    Re: Pinto stroker for rallycross


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    Pinto stroker for rallycross

    Quote Originally Posted by Graham View Post
    Exact, those are the ones. No idea hoe thick the crown is.

    Maybe look at other pistons which are somewhat lighter (non ford)

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    Re: Pinto stroker for rallycross

    those pistons have very thick crowns, i used a set when i built a 2.2 using longer diesel rods and a crank stroked to 80mm, i cant remember how much longer diesel rods are but im pretty sure you will have to machine off more than i did, which is a good thing weight wise and be will be ok on crown thickness as mine were still on the thick side when done, if you already have the pistons measure the crown thickness in the middle, these were something like 24mm you can safely go down to 6mm

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    Re: Pinto stroker for rallycross

    Quote Originally Posted by Graham View Post
    those pistons have very thick crowns, i used a set when i built a 2.2 using longer diesel rods and a crank stroked to 80mm, i cant remember how much longer diesel rods are but im pretty sure you will have to machine off more than i did, which is a good thing weight wise and be will be ok on crown thickness as mine were still on the thick side when done, if you already have the pistons measure the crown thickness in the middle, these were something like 24mm you can safely go down to 6mm
    Graham, what gudgeon pin did you use on this combination and was it retained by a press fit or circlips?
    Slowly gathering some bits for a 2.2 and appreciate your knowledge and experience from your past builds.
    Thanks in advance.

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    Re: Pinto stroker for rallycross

    circlips, those pistons have circlip grooves so go straight on 1600 diesel or cosworth rods

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    Re: Pinto stroker for rallycross

    Quote Originally Posted by Graham View Post
    circlips, those pistons have circlip grooves so go straight on 1600 diesel or cosworth rods
    Top notch info. Thank you.

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