Aluminum rods use in Lake boat?
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Aluminum rods use in Lake boat?

  1. #1
    Senior Member nikwho's Avatar
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    Default Aluminum rods use in Lake boat?

    Hello guys,
    I've happened upon a pretty killer deal on a whole bunch of BBC goodies from a guy locally. He's got a 4 bolt main block, freshly vatted and bored +0.030", a set of 4.280" Venolia forged pistons with big domes, (around -40 to -48 cc's. He doesn't remember and is looking for the paperwork on them. He stated that he remembered that they were supposed to yield 12.5:1 compression with "regular open chamber heads") He's also got a set of Venolia forged aluminum rods (that were ordered with the pistons), a forged Scat internally balance 4" stroke crank, balancer, nice oil pan, nice aluminum timing cover and some other goodies. Everything (except the block, obviously) is brand new and unused. He was still in the parts collecting stage. The rotating assemby has not yet been balanced. I will have the piston to cylinder wall clearance machined/finish honed to be appropriate for use in a boat.

    I'm wanting to build a 700-800 HP NA engine for a lake boat/hot rod that I could spray in the future. Figuring on running a solid roller cam, quality roller rockers and girdle, but haven't gotten to the point of picking those parts just yet. So, I'm not building a super radical engine. I can pick up this block, rotating assembly and other parts for $1,500. I think that it's a good deal for the parts.

    Would it be wise for me to try to integrate these brand new Venolia rods into my build, considering my HP and usage goals, or should I sell the aluminum rods and buy a set of quality forged steel rods, to possibly have a bottom end that will require less maintenance and checking? I've been reading a lot about the forged aluminum rods and it seems that they don't experience the permanent stretch that many talk about. From my reading, the aluminum rods experience approximately 0.010" more stretch during use than steel rods, do to the heat related expansion properties of aluminum than steel. So, I seems like that can be and counted for while setting deck height. I guess guess that I need to figure out if these rods will give me benifits that outweigh diminished long term reliability. I'm sure that it can become quite the discussion between health a that he two. I'm just trying to figure out if I can use these for my application or if I should sell health a that he working he seem and buying steel rods?

    I would love to some day race in the Comp Jet class, but that's not a primary concern with this build. Boat is a '70 Cheetah, 18' and some chage. Berkeley 12-JG pump. Pump will be getting a full rebuild, appropriate impeller, new Place Diverter and a snoop. Will also being researching grates/ride plates/loaders to get the pump set up properly.

    Thanks for any help/advice/guidance!

    Nik

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  3. #2
    Senior Member nikwho's Avatar
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    BTW, I know that I've been very vague as far as exact engine build plans. I've not gotten there as of yet. I'm just trying to figure out if these aluminum rods can be realistically and resonably integrated into my build, or if they are such a specialty part that I should just not consider using them for my applicaton.

    Thanks,
    Nik

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    Senior Member wagspe208's Avatar
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    What are you planning on running for fuel?
    Alum rods have their place... IMO it is on real race pieces with tons of boost, or tons of nitrous.
    For a n/a jet boat.... there are only disadvantages....
    Wags

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    LP-25.com Infomaniac's Avatar
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    If you talk to the alum rod manufacturers. The rods do have a life cycle but it's based on full out passes. Just driving around does not even enter in to reducing the life cycle.

    Contrary to popular belief.

    I wouldn't design a lake engine around them but if you have a combo, crank balanced for alum rods I wouldn't have a problem running them on the lake. And I have many times.
    If For Some Reason I Do Something Worthy Of Recognition. God Provided The Ability And Deserves The Credit.


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    Senior Member nikwho's Avatar
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    I'd be okay with race gas or blending. The rotating assembly isn't yet balanced, so I could sell the Venolia alum rods, I suppose, then buy some steel rods. But, the more I read, it seems that there are a lot of misconceptions about aluminum rods. I just don't want to run them if I can sell this brand new set to someone that needs them and buy or trade for a set of steel H beam rods, for little or no money out of pocket. I'll certainly need to decide before I get the assembly balanced.

    On the topic of the aluminum rods, would the crank tunnel/oil pan rails need to be clearanced for aluminum rods? Or is it normally not needed with just a 4" stroke?

    Thank you!

    Nik

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    Red Blooded American The Doctor's Avatar
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    Quote Originally Posted by nikwho View Post
    . . . On the topic of the aluminum rods, would the crank tunnel/oil pan rails need to be clearanced for aluminum rods? Or is it normally not needed with just a 4" stroke?

    Thank you!

    Nik
    Your initial mock-up should make this abundantly clear.
    The best things in life aren't things!

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    Or Seth, either one Budweiser's Avatar
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    Personally, I'd have little concern running them on a 4" stroke, likely at less than 7000 rpm in a lake boat, used as a lake boat.

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    Senior Member jockorace's Avatar
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    Old school rule of thumb was replace after 100 runs. (1/4 mile I assume). JMO, I would sell them while they are NEW. They are worth next to nothing once they are "used". Jocko

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    Or Seth, either one Budweiser's Avatar
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    I've told this story before, but I'll let it rip one more time...

    About 20 years ago my best friend (yup, a "friend of mine" story) built a 512 (stroked 440 MOPAR). It was one of those "best of everything" kind of builds. Indy clyinder heads, Jessel rockers, Jessel belt drive... You get the point. Anyway, he called and spoke to Bill Miller on the phone about using his aluminum rods. As the story goes, Bill Miller assured my buddy that his aluminum rods would outlast the other components for his particular application, which is 99% street driven, maybe a blast down the track every couple of years. Pump gas engine, 750 hp @ 7200rpm on the dyno (which was damn respectable back in the day and is still no slouch)

    Here we are, 20 years later. The car is used like a boat, only summer time, occasional extended cruises (100+ mile, one way)... And every time it's out, it get's the piss wrung out of it, 7200 RPM shifts, bumping the 7500rpm limiter every so often. Solid lifters have broken, been through a few transmissions, blown out U joints... Rods are still in the block. 20 years.

  12. #10
    Senior Member nikwho's Avatar
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    Very interesting! They way you were starting to set that story up, I was expecting a story that would scare me away from aluminum rods!

    Doc, I suppose that I could do a mock up. I was just trying to think of anything else that might have started to sway me away from the aluminum rods. I was thinking that If I was steering away from using those rods, that I'd want to handle them as little as possible, so I could sell them easily if that was the way that I wanted to go.

    I do appreciate everyone's input. I don't want to try to make my engine more than it is or will be. I don't feel a need to run the alum rods just so that I can say that I am. I want to build a solid mill that'll push my boat across the lake pretty quickly. I like the thought of running them just for the sake of doing something a little differently.

  13. #11
    Senior Member nikwho's Avatar
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    Also, the 4" Scat crank is an internal balance crank. If I switch over to heavier steel rods, might I be creating an issue with balancing this rotating assembly internally? I appologize for any questions that I ask that are kinda dumb or seem obvious to the masses. I'm just trying to be thorough and make good choices.
    Last edited by nikwho; 05-07-2017 at 10:12 PM.

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    FWIW........When doing an engine build......A mock up is a major part of it...IMO...there are spots in there that the clearance needs to be looked at....end play's need to be checked ect...JMHO....

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    if starting out new i would sell the aluminum rods and get a set of steel rods.the fatigue factor for the aluminum rod vs steel rods is my reason for this.yes the aluminum rod will work but the steel rod will last 10 times longer before they fatigue.wags hit the nail on the head.aluminum rod has it,s place in certian race engines but not really intended for long term use.

  16. #14
    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by nikwho View Post
    Very interesting! They way you were starting to set that story up, I was expecting a story that would scare me away from aluminum rods!

    Doc, I suppose that I could do a mock up. I was just trying to think of anything else that might have started to sway me away from the aluminum rods. I was thinking that If I was steering away from using those rods, that I'd want to handle them as little as possible, so I could sell them easily if that was the way that I wanted to go.

    I do appreciate everyone's input. I don't want to try to make my engine more than it is or will be. I don't feel a need to run the alum rods just so that I can say that I am. I want to build a solid mill that'll push my boat across the lake pretty quickly. I like the thought of running them just for the sake of doing something a little differently.
    This is just me personally... If I were in your shoes, I'd run 'em. "Run what ya got". However, I don't think I'd choose to purchase aluminum rods for a build. There's knowing how well they've worked out for my buddy, and there's also "knowing" the generally accepted old school rule of thumb... and having it rolling around in the back of my mind. For no reason, other than peace of mind, I will always choose steel rods... Unless, I just coincidentally happen to have aluminum rods.

    So, if it's always gonna be in the back of your mind, sell 'em. But, assuming everything's set up and tuned well, I don't think you'll have any issues with them. Poor set up and tune can kill a steel rod just as quick.

    If you choose to run them, make sure to do your homework. They are set up differently to account for rod growth as they heat up and possible stretch.
    Last edited by Budweiser; 05-08-2017 at 08:33 AM.

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