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I've ran both strokers and if you're looking for a lightweight crankshaft, the 4" 408" crank is hands down lighter, to the tune of 6-8lbs for a typical Scat 9000 casting.
That would depend on how much effort the supplier puts into the design to make it lighter. I see no reason why a 3.85" crank would be heavier in principle. But I'm sure you're right that in practice, many 4" stroke cranks are lighter.
 

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A 3.85" crank is nice if you planned on rebuilding a 351W and instead of regrinding the original crank you get the stroker crank with no further cost over a regular rebuild.

When building a 500 hp monster, you might as well build a 408 right away.
 

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Discussion Starter · #24 ·
So if they are internally balanced, that means I would also have to get a new flexplate and harmonic balancer with 0 imbalance, correct? Are all stroker kits this way, or can you get a 28 oz imbalance 408 kit?
 

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So if they are internally balanced, that means I would also have to get a new flexplate and harmonic balancer with 0 imbalance, correct? Are all stroker kits this way, or can you get a 28 oz imbalance 408 kit?
Most stroker kits offer both 28 oz and "zero balance" versions.
 

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My 393 needed a ton of drilling on the counterweights to get it to balance at 28oz and was more expensive than a typical balance job. Getting it to 0 balance would be a ton of work, if possible at all. This is the only stroker I've built but I get the impression the 0 balance goal is a 302 thing, not a 351 thing. A question to 408 builders, were your results any different?
 

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My 393 needed a ton of drilling on the counterweights to get it to balance at 28oz and was more expensive than a typical balance job. Getting it to 0 balance would be a ton of work, if possible at all. This is the only stroker I've built but I get the impression the 0 balance goal is a 302 thing, not a 351 thing. A question to 408 builders, were your results any different?
Who knows how much it would cost to make a 28 oz into 0, or vice versa? Adding Mallory weight to do the balance swap is kind of a waste of good money when the proper weight crank is available.

One doesn't "need" to go 0 balanced on most builds unless you're going to be turning higher RPM's (typically 7K+.) Of course, the balancer and flywheel/flex plate would also need to be upgraded to 0 balance too. Some of those that are 28oz have removeable weights that can create the 0 balance needs.
 

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Discussion Starter · #28 ·
So would this be zero balance because the "Balance Type" is "Internal"?
Font Parallel Rectangle Number Screenshot
 

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But I will admit, this is confusing. The SBF is externally balanced with the 28 or 50-oz balancer and flexplate or flywheel (they must be a matched set). I do not see any talk of a Zero oz setup. The kits indicate they need to be internally balanced.

I purchased my Eagle kit and it did say it needed to be internally balanced. The shop I shipped it to needed a 28-oz balancer and flexplate. My only guess is it needed the non balanced crank, balanced for the different rods and pistons to make it work with the 28oz balancing?

This is what Eagle has to say about it: https://eaglerod.com/balancing
 

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Yes, the description is confusing. All factory 351w's are 28oz imbalance and it never changed for them like Ford did with the 302's when the later ones were 50oz.

Aftermarket 351w cranks are 28oz or 0 imbalance. Before I bought from the above vendor I would verify what they mean as the ad is misleading. Some vendors will say that they can be balanced either way. Yes, many can BUT no matter what, balancing will be on your dime according to them since they say they are not balanced. Balancing costs depend on how close the rotating assembly would be to the desired imbalance need, vs how it is when you get it. Labor and materials (Mallory heavy metal) cannot be determined in advance.
 

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So would this be zero balance because the "Balance Type" is "Internal"? View attachment 869324
Yes, it's confusing. No, it would not be "zero balanced". It would be unbalanced. Whether you chose to have the assembly balanced to the standard 28.2 oz/in or zero balanced would be up to you and how much you want to spend on Mallory Metal....
 

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So would this be zero balance because the "Balance Type" is "Internal"? View attachment 869324
Since the line there specifies "internal" (the alternative being external balance) I think that YES, that means a 'zero balance' crank. All stock Windsors are externally balanced, intended to have a counterweight on the damper and flexplate/flywheel. This one would require a flexplate/flywheel and damper combo that has no counterweights.

My take on this is that it's intended to be a "zero balance" crank, with enough weight in the counterweights to match typical rod/piston combos, once you get it professionally balanced.

The bit about "rotating assembly unbalanced" means they don't have it weighted to match any particular piston and rod combo from the factory, and isn't intended to be bolted up and run without machine work.

As an aside, the 50 oz. "5.0" cranks weigh less and have less steel in them than the earlier 302 cranks with the 28 oz external balance. Ford did it to reduce material costs. Static balance on both is basically the same, and it makes no difference at lower RPMs. However, at high rpms, the earlier but slightly heavier cranks do not have as much dynamic stress, with the counterweights more directly working to balance out the reciprocating mass. Internal balance puts less stress on bearings, and wastes less energy with the crank flexing and putting pressure on the mains and block to keep it straight at very high RPMs. For an engine that never gets above 5500 rpms, this is 100% a nonissue, in regard to 50 oz, 28 oz, and "zero balance".
 

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If you read the article that I posted from Eagle, they purposely put a little extra metal on the crank so that when balancing, metal can be taken off, and not added. I believe this removal brings it into spec for a 28oz external balance. But I am not a machinist, so I can not say for sure, but that is what they did to my rotating assembly.
 

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I would recommend that you find a local machine shop that you want to perform the work. At a minimum they will be doing the boring but you may prefer them to perform balancing and assembly as well. They will probably have recommendations on the balancer/flywheel as well as other things that pop up like oil pumps and oil pans etc.

I learned the hard way that buying parts online and bringing them to a machinist to assemble can have conflicts, but hey I’m building a sbf 427w so your mileage may vary
 
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