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Old 09-21-2015, 08:44 AM
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Ive seen several supercharged marine engines making in excess of 900hp with eagle 4340 cranks , without issue. I personally have chevy forged steel cranks in my engines, at 800hp for 4 years now, and prior to that, several years at 600+hp.

Im no expert on cranks, but i beleive it isnt just HP you need to consider. The machine work , main cap material, engine stroke, RPM all play a factor. Theres no doubt a 4 inch stroke turning 5500rpm, can get away with a weaker crank, than a 7500rpm, 4.5 " stroke.

4340 is a stout forging. Ive also been told for marine, a counterweighted crank is a better way to go.
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Old 09-21-2015, 09:26 AM
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I've got vortech charged 540s. Makes just shy of 800HP

Running Callies cranks, carillo rods and JE pistons.
Dart Pro 1heads

Crane 741 cam. You need long risers with this cam, maybe even full dry exhaust if you can!
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Old 09-21-2015, 10:17 AM
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The crane 741 cam works great in a blown 502/540. The 651 crane cam, works very well in a blown 540-565ish build.

I have two friends that have 540s that made 900 and 950hp , and a nice flat torque curve with the 651 cams. For an off the shelf series of cams, they do very well.
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Old 10-02-2015, 11:28 PM
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I personally use Callies cranks & oliver billet rods in my personal motors. But have built several motors with scat cranks & rods, they mic up great, and are still running strong. Its all about your budget, and personal preference. I would NEVER use eagle, not even in a lawn mower. I totally agree with Mild Thunder about cam choice. I have used the 651 cam in several blower motors for people with great results. If you have a custom grind done call Bullet cams, they are great guys, do it for a living and know their stuff. Not to mention they won't bend you over or sell you a cam that won't work as they say.
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Old 10-03-2015, 09:36 AM
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No Eagle ?? That`s not very American of you!

My dummy lawnmower choo choo motors have Eagle crank and rods.
How come you no like?


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Old 10-03-2015, 10:21 AM
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If your looking for a good bang for the buck check out Molnar Technology. Better then eagle and scat. The owner has also been involved with Oliver and contracted for carillo. He knows his stuff with cranks and rods.

http://www.molnartechnologies.com
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Old 10-03-2015, 11:54 AM
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here is my opinion,eagle crankshafts are machined with journal sizes all over the place.they are a pretty good forging.scat is priced about the same as eagle ,they are a good forging and they machine them on size.i don,t use the eagle cranks anymore because i got tired of playing the mix&match game with the bearings,it just takes to much time.for the lower hp&rpm engines the scat crank is a good choice.for the bigger power supercharged engines i like the callies magnum crank.
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Old 10-03-2015, 12:47 PM
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Seems like lots of guys argue crank brands. Some things to consider when purchasing/comparing cranks.

Forging. Most BBC aftermarket cranks, are 4340 Forged. This is a very strong forging in itself, and stronger than the old 1053 and 5140 Forging GM steel cranks. Eagle, Scat, lunati, howards, Callies, etc, are 4340 Forged pieces.

Then theres the american vs imported. Some cranks, are 100% forged and finished here in the US. Normally, you pay for this cost wise. Some cranks, are forged overseas, and finished here. Some are forged AND finished overseas. Eagle was one of them. I believe for a while there, Eagle cranks were notorious for the clearances and final finished product, to well, be all over the place. I cannot verify, but a few builders I have talked to, have said they have cleaned up their stuff, and they are a nicer product, than they were 15 years ago. Whether or not that is true, I don't know. But, I do know, about 10 years ago, I got bit by eagles tolerances.

There's different Filet Radius, seems like the standard for most aftermarket 4340 cranks, is .125, this is an area that can increase strength . Then there is the finishing process companies perform that may differ (stress relieving, etc), and nitriding procedures that may differ. Oiling holes, etc etc

The, there is the lightweight vs standard weight stuff. Something rarely mentioned when crank coversations come up, is the use of centerweights. whether or not the crank has counter weights Some cranks have them, so do not. I was told that for an offshore engine, having the center counterweights, is the way to go. Due to the fact the counterbalance is effectively corrected at that point of the crankshaft, instead of relying on counterweights at the ends of the crankshaft. With longer strokes, this helps eliminate crank flex, extending bearing life, and ultimately, the life of the crankshaft itself. It makes for a heavier crankshaft, but as we know, Marine and endurance engines, may not benefit, from the things drag race engines do, and vice versa. Crank manufactures know this, therefore, they have options per the application. (kind of verbatim wording there from some literature)

Just about all the companies out there now, have options. To say a "scat" crank, is not gonna work as good as a "callies",or anyone else, is too vague. For one, callies has a compstar line, that is forged overseas and finished here. Surely not the same crank as their "magnum" line. Scat, also forges overseas, BUT, does offer a USA forged crankshaft, WITH center counterweights. For example, compare these two crankshafts.

Scat 4.25 Stroke 4340 Cranks.

4-454-4250-6385 This crank has NO center counterweights. It is forged overseas. Weighs 70lbs Summit price is $796.00

4-454A-4250-6385-C This crank HAS center counterweights, it is forged in the USA from Pacific drop Forge, weighs 75lbs, and summit price is $1981.00

Same brand, same material, same stroke, two entirely different crankshafts. They also offer superlight, and procomp lightweight series cranks, in the same stroke, etc. These also do NOT have center counterweights.

So, out of four BBC 4.250 Stroke 2pc rear seal, , 4340 Forgings scat offers, in my eyes, 1 of them, would make an excellent offshore crankshaft.

Many things to consider when purchasing a crank, and it goes much deeper than the label on the box. Most companies now offer different levels of forgings and processes, and generall, I think you get what you pay for in this department. Also, the best crankshaft in the world, isn't going to end concerns, if you are running a block that is prone to web cracking at certain rpm/power levels, ductile caps, and so on. For a guy running a production block like me, with ductile caps, good chance you'll run out of block, before you run out of crankshaft.
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Old 10-03-2015, 12:50 PM
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Originally Posted by offshorexcursion
If your looking for a good bang for the buck check out Molnar Technology. Better then eagle and scat. The owner has also been involved with Oliver and contracted for carillo. He knows his stuff with cranks and rods.

http://www.molnartechnologies.com
I believe he also started K1 technologies too.
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Old 10-03-2015, 01:01 PM
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Originally Posted by ICDEDPPL
No Eagle ?? That`s not very American of you!

My dummy lawnmower choo choo motors have Eagle crank and rods.
How come you no like?


]
Eagle offers with and without center counterweights in your application. From eagles 2014 Catalog

"Eagles forged 4340 steel crankshafts are forged from SAE 4340 steel, feature a non-twist forging, multi-stage heat treat process, stress relieving, shot peening, and nitriding for superior strength and reliability in the most demanding applications. Each journal is micropolished to a 3 RA or better. A .125 Radius is used to increase strength, so chamfered bearings must be used. Longer strokes feature center counterweights for stability, and durability. They are the perfect choice for applications up to 1500HP. Approximate weight is 70-78lbs. "

$737.00 with counterweights
http://www.summitracing.com/parts/esp-445442526385

$729.00 without.
http://www.summitracing.com/parts/esp-445442546385
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