where to save weight rod or piston
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where to save weight rod or piston

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    Default where to save weight rod or piston

    if you had the choice to save weight on the piston or connecting rod which would be more important my logic tells me in the piston the reason I ask is that I haven't ordered pistons yet and I might go with a longer rod to save on piston weight

    Its for my 396 that im building I bought some scat 6.135 rods and can still go to 6.385 if it would benefit me at all
    im shooting for 1.5hper cube and I think im on the right track so far but to get the 14:1 compression I want the domes are going to be very large and im trying to save some weight anywhere I can

    thanks
    Tyler

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    Quote Originally Posted by bowtiebro View Post
    if you had the choice to save weight on the piston or connecting rod which would be more important my logic tells me in the piston the reason I ask is that I haven't ordered pistons yet and I might go with a longer rod to save on piston weight

    Its for my 396 that im building I bought some scat 6.135 rods and can still go to 6.385 if it would benefit me at all
    im shooting for 1.5hper cube and I think im on the right track so far but to get the 14:1 compression I want the domes are going to be very large and im trying to save some weight anywhere I can

    thanks
    Tyler
    Go with the longer rod. You'll have to order custom piston because I don't know of anybody making pistons for that rod.
    Better yet, go with a Eagle 6.635 (+.500) rod and a 1.27 compression height.
    Both the 6.385 and 6.635 rod are a walk in the park for the 427. Pistons are sitting on the shelf for both, they're just labeled for use with a 4.25 crank.



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    is the oil ring going to be on the pin with the +.5 this isn't a drag only deal.... guess the piston would be the same compression height as a 4" stroke with 6.385 but I have never looked at how much room they had on there ring pack

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    Quote Originally Posted by bowtiebro View Post
    is the oil ring going to be on the pin with the +.5 this isn't a drag only deal.... guess the piston would be the same compression height as a 4" stroke with 6.385 but I have never looked at how much room they had on there ring pack
    Its the same compression height as a 4.25 crank with a 6.385 rod. Yes, the pin is in the oil ring. If that bothers you, go with the 6.385 rod.



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    Didn't want to muddy up the thread earlier, but seeing as it seems resolved...

    I've been curious, why aluminum rods aren't more widely used, especially in a marine application. And why aluminum rods have a fatigue life stigma, yet aluminum pistons do not?

    How much of the stigma is just urban lore? I admit I have reservations based off no real reason, even though I know of at least one engine (4.25 stroke, 7200 rev limited) with Bill Miller rods that's been trouble free for over 10 years (10,000+ miles and a lot of time on the limiter).

    What's the real deal?

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    Quote Originally Posted by Budweiser View Post
    Didn't want to muddy up the thread earlier, but seeing as it seems resolved...

    I've been curious, why aluminum rods aren't more widely used, especially in a marine application. And why aluminum rods have a fatigue life stigma, yet aluminum pistons do not?

    How much of the stigma is just urban lore? I admit I have reservations based off no real reason, even though I know of at least one engine (4.25 stroke, 7200 rev limited) with Bill Miller rods that's been trouble free for over 10 years (10,000+ miles and a lot of time on the limiter).

    What's the real deal?
    think everyone has steered away from them for at least a few reasons, wives tales and material cost, the piston prolly doesn't fail due to it having twice the bearing surface as the rod holding it (two contact points instead of one)

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    Quote Originally Posted by Budweiser View Post
    Didn't want to muddy up the thread earlier, but seeing as it seems resolved...

    I've been curious, why aluminum rods aren't more widely used, especially in a marine application. And why aluminum rods have a fatigue life stigma, yet aluminum pistons do not?

    How much of the stigma is just urban lore? I admit I have reservations based off no real reason, even though I know of at least one engine (4.25 stroke, 7200 rev limited) with Bill Miller rods that's been trouble free for over 10 years (10,000+ miles and a lot of time on the limiter).

    What's the real deal?
    Bill Miller are the best aluminum. Rod on the market. I like them allot.

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    Quote Originally Posted by Budweiser View Post
    Didn't want to muddy up the thread earlier, but seeing as it seems resolved...

    I've been curious, why aluminum rods aren't more widely used, especially in a marine application. And why aluminum rods have a fatigue life stigma, yet aluminum pistons do not?

    How much of the stigma is just urban lore? I admit I have reservations based off no real reason, even though I know of at least one engine (4.25 stroke, 7200 rev limited) with Bill Miller rods that's been trouble free for over 10 years (10,000+ miles and a lot of time on the limiter).

    What's the real deal?
    Aside from having 2 load bearing points, the piston only has to deal with its own weight on the intake stroke, and it doesn't include the pin. The rod as to deal with it all from the fork up. Most aluminum rounds don't fail at the small end, they fail mid beam, or where the rod transitions into the fork, or as Rocky Childs called it, "the hinge"



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    The further away form the center of the crank, the more effect the weight will have.
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    Acts 2:38, the perfect answer to the perfect question.

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    Scott,

    So you are thinking a alum rod would live in a river/enduro application? With advances in metals and bearing these days I dont see why it wouldnt if you had the budget. On the flip side I would think if that was the case then NASCAR or some of the car enduro motors would have already gone that route.

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    Quote Originally Posted by desrtrat256 View Post
    Scott,

    So you are thinking a alum rod would live in a river/enduro application? With advances in metals and bearing these days I dont see why it wouldnt if you had the budget. On the flip side I would think if that was the case then NASCAR or some of the car enduro motors would have already gone that route.
    The only application I see for aluminum rods these days is where the bottom end needs a little cushion from extreme cyl pressures. Other than that I don't see the need or benefit from aluminum rods. The biggest problem with them is they're a ticking time bomb. it's not a matter of if, only when...unless you're using them in a completely unrelated application like a low hp/low rpm street engine where you're not using them even remotely close to their intended use but that's not a fair comparison. Not sure of anyone mentioned windage issues, either. Big, fat, bulky alum rods don't help in that department. ONe last thing to consider; weight in a recip. assembly does not contribute or detract from overall power, it only helps in acceleration of the masses. If the application is endurance or any other app where the rpm is more continuous then IMO the weight savings is really of no benefit over the reliability concerns. Steel rods with the lightest possible piston will usually be a better combination.
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    Re: Alumi rods... I've heard of a couple people running them at Bonneville with success.

    I couldn't find the video of the truck that ran them, but I know of a mini-truck that ran them in an Esslinger 2.9ltr Pinto engine in this series


    You really can't get much more abusive than that type of racing. If I recall correctly they were GPR's, but I'll check. The engine builder called them " poor man's Ti rods" he claims the engine rev'ed quicker.

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    Quote Originally Posted by desrtrat256 View Post
    Scott,

    So you are thinking a alum rod would live in a river/enduro application? With advances in metals and bearing these days I dont see why it wouldnt if you had the budget. On the flipside I would think if that was the case then NASCAR or some of the car enduro motors would have already gone that route.
    Adding to what Scott posted, all the lower cost aluminum rods like Manley, Super Rod, Howards are history. GRP, MGP, Miller, and Alan Johnson/C&A are not cheap. If you have to replace them once, you could have to replace them just once, you could have bought a set of best steel rods with the very best bolts.

    Comparing a street driven car with even a recreation lake boat is a bad comparison. Stock GM dimple rods do quite well in 750 HP street engines. See too many 750HP plus boats running stock rods??

    Nascar isn't allowed to run aluminum rods, and even if they did, they would replace them every race. They can run them in Indy and F1, but they don't.



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    Quote Originally Posted by Sleeper CP View Post
    Re: Alumi rods... I've heard of a couple people running them at Bonneville with success.

    I couldn't find the video of the truck that ran them, but I know of a mini-truck that ran them in an Esslinger 2.9ltr Pinto engine in this series


    You really can't get much more abusive than that type of racing. If I recall correctly they were GPR's, but I'll check. The engine builder called them " poor man's Ti rods" he claims the engine rev'ed quicker.
    Abusive is a understatement when it comes to short course or desesrt racing. But the short course guys only have to run 4 short races a weekend then the motor comes out to get checked.

    GN7, Side question. Do you have to run a roots style blower per GN rules? or can it be centrifugal?

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