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Old 04-13-2010, 06:20 PM
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Balancing An Sledgehammer Crankshaft

As the title says Balancing a Lunati Sledgehammer crankshaft.I Have been collecting parts this past two years for a one piece seal block Chevy 383 build.and finally took my crank to the balancer in the UK.Also took my Scat H beam 5.7 rods and Mahle pistons+shells,The initial quote was 180 +VAT.(Sterling) Now to day i have been informed that i will need another 7or 8 slugs of mallory to get a balance(another 200 Sterling)
If i had read these excellent forums a few years ago i would of bought a balanced rotating assembly.
So what options do i have now? pay up or maybe someone here knows a combination of rod+pistons that would be easier to balance to a Lunati Sledgehammer crank or worst case another crankshaft .Shipping to Ireland is expensive so pistons and or rods would be first choice.
SORRY FOR LONG WINDED POSTING.----ps Internal balance.

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Old 04-13-2010, 06:55 PM
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Quote:
Originally Posted by technicaltom
As the title says Balancing a Lunati Sledgehammer crankshaft.I Have been collecting parts this past two years for a one piece seal block Chevy 383 build.and finally took my crank to the balancer in the UK.Also took my Scat H beam 5.7 rods and Mahle pistons+shells,The initial quote was 180 +VAT.(Sterling) Now to day i have been informed that i will need another 7or 8 slugs of mallory to get a balance(another 200 Sterling)
If i had read these excellent forums a few years ago i would of bought a balanced rotating assembly.
So what options do i have now? pay up or maybe someone here knows a combination of rod+pistons that would be easier to balance to a Lunati Sledgehammer crank or worst case another crankshaft .Shipping to Ireland is expensive so pistons and or rods would be first choice.
SORRY FOR LONG WINDED POSTING.----ps Internal balance.
When you start talking Mallory metal, you start talking a lot of imbalance. So I'd ask how far off is this?

I'm surprised that a forged 4340 shaft needs so much weight to balance up with with SCAT H beams and Mahle pistons. But I haven't used a Lunati shaft so haven't direct experience with this combo.

I'd also what to know where its imbalanced. One solution can be to drill lightening holes in the crank pins where they don't exist and enlarge those that do. Taking a look a picture of this crank it appears the center two pins are solid, is this true?

I suppose there's no real harm in going to external balance. Shafts aren't throw by throw balanced anyway, they have most hanging on the ends of the front and rear pins. So carrying the remainder outside the oil seals isn't that big of a deal for a street motor. Which of course begs the next question of what you're going to use this engine for?

Bogie
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Old 04-13-2010, 07:29 PM
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Hi Oldbogie. Thanks for input,the engine is for an off road race car, dirt track that is very light and is direct drive(no transmission)just a flywheel and clutch+bellhousing.also very short duration races 4 to 7. 1/4 mile laps 3to6 races a day.6800 To 7200 RPM for a few seconds each lap( on a dry day anyway) The balancing shop is in the UK as i mentioned above ,that is a ferry trip +many hundreds of miles road away from me.
I am of the opinion that im going to " buy some experience here" , As i have no transmission i need the revs and Balancing is critical to the engine surviving any lenght of time.Also i have neutral balance flywheel+crankshaft damper/front pulley (whatever you call it).
I have tried a few e mails to lunati without any replys to see if they could recommend a combination of parts Compatable with their crankshaft that i could purchase from them.Allthough not relevant to this post i find that lack of response very annoying, hey i wanted to spend money with them!
One final note of interest the "Sledgehammer"c/ shaft is supplied with some heavy metal allready installed.
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Old 04-13-2010, 07:30 PM
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Why not contact Lunati and see what they have to say about this.
Guy
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Old 04-13-2010, 07:36 PM
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Sorry,you posted before I did !!!
Guy
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Old 04-13-2010, 07:47 PM
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Quote:
Originally Posted by technicaltom
Hi Oldbogie. Thanks for input,the engine is for an off road race car, dirt track that is very light and is direct drive(no transmission)just a flywheel and clutch+bellhousing.also very short duration races 4 to 7. 1/4 mile laps 3to6 races a day.6800 To 7200 RPM for a few seconds each lap( on a dry day anyway) The balancing shop is in the UK as i mentioned above ,that is a ferry trip +many hundreds of miles road away from me.
I am of the opinion that im going to " buy some experience here" , As i have no transmission i need the revs and Balancing is critical to the engine surviving any lenght of time.Also i have neutral balance flywheel+crankshaft damper/front pulley (whatever you call it).
I have tried a few e mails to lunati without any replys to see if they could recommend a combination of parts Compatable with their crankshaft that i could purchase from them.Allthough not relevant to this post i find that lack of response very annoying, hey i wanted to spend money with them!
One final note of interest the "Sledgehammer"c/ shaft is supplied with some heavy metal allready installed.
Can you get us the typical weights of the rods and pistons. Although, I don't have a Lunati rod and piston from their balanced combination to compare. All they do is talk about balanced within 1.5 gram, what I want to know is whether we're talking 550 or 800 gram rods.

Yeah I know they come with some heavy metal in them, you'd think they were cast iron where you can't get enough mass in the counter weights to offset the pin, rod, and piston instead of a high density forged 4340 chunk of metal.

I'm getting out of the shop and going home for some dinner it's like 6:45 PM Pacific Daylight Time here on the west coast of the US, isn't this like the wee hours of the morning for you?

Bogie
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Old 04-13-2010, 10:52 PM
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Part of the difficulty revolves around the one piece rear main style crank, that usually requires an external balanced flywheel. In that he's using a neutral balanced flywheel, this adds to how much extra internal heavy metal is needed.
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Old 04-14-2010, 05:09 AM
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Quote:
Originally Posted by oldbogie
Can you get us the typical weights of the rods and pistons. Although, I don't have a Lunati rod and piston from their balanced combination to compare. All they do is talk about balanced within 1.5 gram, what I want to know is whether we're talking 550 or 800 gram rods.

Yeah I know they come with some heavy metal in them, you'd think they were cast iron where you can't get enough mass in the counter weights to offset the pin, rod, and piston instead of a high density forged 4340 chunk of metal.

I'm getting out of the shop and going home for some dinner it's like 6:45 PM Pacific Daylight Time here on the west coast of the US, isn't this like the wee hours of the morning for you?

Bogie
Hi Bogie, Thanks for your reply and other posters, yes its the wee hours here in Cork, i have developed some bad habits now that work is scarce and i dont have to get up so early ,so reading forums sometimes goes on and on and on,late at night. The Scat conrods are light i would guess in the 500G range i will check on google later. pistons are light as well,one thought would be to go with 6" rods and then the pistons would be lighter,(would the longer rods be heavier?) I will have to admit my knowledge of V8 balancing is limited.
I can see the one piece seal Crankshaft has less metal at the flange area.
I have sent another e mail to Lunati just now
i suppose a bit of Dollar saving up, is another option and buy a balanced rorating assembly then use the difficult to balance Crankshaft+rods and pistons later on when i work out a solution.Just a pity the" Celtic Tiger " years have passed and money is tight.
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Old 04-14-2010, 09:47 AM
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Quote:
Originally Posted by technicaltom
I can see the one piece seal Crankshaft has less metal at the flange area.
Is the concept of external balancing out of the question? I know you said this is direct drive w/o tranny, etc,. but wonder that the internal vs. external is costing you more than it might be worth in regards to the added heavy metal required for balancing.
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Old 04-14-2010, 05:43 PM
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Hi just for the moment i will leave the external balance option alone.however to day i recieved an e mail from the shop with my balance job, and the following figures were mentioned ,the crankshaft needs 57G on the front and 147G s on the rear of the crankshaft.Thats going to require 3 slugs of heavy metal (screw in type) so the crankshaft needs sending out to be drilled and tapped, I will "BITE THE BULLET " and just pay up and treat it as a lesson learned. In future i must ask for advice Before rather than after ,
Anyway thanks for the input from the various posters i have learned a lot and spent some time reading up on Balancing on this forum and on the Net in general this evening.
So my cheapish forged Lunati sledgehammer crankshaft what with shipping to Ireland then balancing in the UK at 400 pounds sterling is now an expensive item , pity im too old to emigrate to the USA. I will post again when its all built up. Tom
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