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carrillo rods combo

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  • carrillo rods combo

    I found these carrillo rods and pins on fleabay the other day.
    Length: 6.450"
    Big end width: .900
    Big end Bore: 1.976
    Pin end bore: .7874 (20mm)
    Pin end width: .700
    Weight: 555 grams +/-
    Crank Journal: 1.850
    Bolts: 3/8 CARR
    They are .009" shorter than KA rod. And .076" narrower. This means if I deck the block .010" and use a boxed piston, and piston guide the rod,they may work. I already run custom pistons, so the price will not be alot more.
    I will have to turn the crank to a Honda race bearing. Since I already have a crank that has been lightened 4lbs this will give me a very light rotating assemble.
    These are Ford nascar rods and are very cheap. They have (2) races on them. They will stand up to 900hp in a cup motor so I don't think I can hurt them in a Prod. motor. I bought a set for $300. new they cost about $3000.
    This will give parts for (2) motors.
    Tell me what you think, and any problems I may have over looked.

  • #2
    Just a few things to consider, not saying I know that much but:
    - Just because they handle 900 hp in a cup motor, doesn't mean they will handle 900 4 cylinder. Obviously roughly speaking the might be optimised to ~112hp/cyl, 155hp/litre @ ~16 Bar BMEP for cup-lifes which if I recall is still pretty racey - 600-1500 miles or something? Consider those - but speaking NA you'd be doing exceptionally well to match or exceed a cup motor.

    While BMEP / specific torque would be something of real-relevance to consider, crucially they will be engineered for the piston accelerations / forces in action. Big concern there would be if you're pistons are significantly heavier than those in the cup engine - you'd be adding more force at lower speeds/accelerations than the cup configuration affecting the life commensurately.

    However, I assume talking SR/KA/CA you'll be a lot slower than Cup so even if heavier you'd be more than fine. Just consider matching pin-bore clearances/finish appropriately as the cup-motor might have a snazzy DLC pin or something exotic (if allowed)

    Piston weight ~500g-ish for Cup so as long as you're not 650g+ you should be more than fine and benefit from a nice bit of kit.

    ALTHOUGH, re-reading and seeing you're info on the parts. 2 races would be probably over half their life or more used up. (not sure how much they'll use the same engines in practices/qualifying. But if the rods are actually still lifed to 800 miles (as per the link above - I have some race-engine technology publications with more info but can't remember if they've increased that recently. Then 2 races in a cup motor will be maybe 5-80% of their life used, if they're so marginal as to be good for only that, you'd have to consider the loading and life you want from them a bit more IMO. they'll still probably be ok, but if they're so marginal (considering weight they don't sound massively weight optimised/marginal), then you really would nee to consider the loading you put on them and the life you expect. Obviously being steel, and hopefully (unless you have crap heavy pistons) you'll be putting much lower loads on them, and in fatigue terms 10 or 20% would probably be sufficient for them to last thousands/100,000's of thousands of cycles more than they would at cup duty.


    • #3
      An aftermarket SR piston + pin is quite a bit lighter than 500 g IIRC. Usually in the ~400g range with pins I believe (about 350ish g without the pin or so).

      Plus steel has an endurance limit, which I doubt you're loading them to, so they'll probably be fine for essentially ever at your power level.
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