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Author Topic:   5140 vs. 4340
posted January 20, 2004 09:09 AM
My question is what kind of horsepower and rpms is a 5140 crank good for. I'm just wondering if there is a decent alternative to the six or seven hundred dollar 4340 cranks for lower horsepower lower rpm motors. I appreciate any help. Thanks

posted January 20, 2004 10:14 AM
And for comparison...

A stock cast crank is about 90,000-95,000 PSI.
Elasticiy of cast is around 5%-6% and steels is around 15%. Steel will 'bend' a little where cast cracks or breaks.
Stock 1053 steel forgings are around 105,000 PSI.

posted January 20, 2004 12:55 PM
What i think dirtracer and many others would like to find out is what are the limits on the 5140/4130 cranks vs 4340. Never mind the ultimate stregnth, yield strength, etc. What HP or rpm are they able to stand up to repeatedly. for example: If we are building 550HP 7200rpm engines and a 5140 crank will stand say 650HP and 8000rpm then we could save 3-400$ over buying a 4340 crank that can take 1000HP which it will never see.

posted January 20, 2004 02:55 PM
i think your rpms will depend mostly on the overall weight of the rotating assembly. lighter rods and pistons are easier on cranks than heavier parts. also your stroke comes in to play. the longer the stroke the less rpm you can run before it breaks...assuming everything else is equal.

as for horsepower that all depends on the track you run. big tacky tracks with high speeds are alot harder on cranks than a small dry 1/4 mile with peaky rpms.

overall if i was gonna build a 383/406 or larger i would go with 4340 (callies).
short stroke combos i believe can get by with a GOOD 5140 crank...355's 377s ect.

hope this helps.


posted January 23, 2004 10:50 PM
Stock car, Im gonna have to disagree with ya! Actually, short tracks are worse for a crankshaft due to being on and off the throttle so much. At a big track, you are on the throttle more consistently for a longer period of time. The rpm's you turn is all a matter of gearing. By the way, dont be afraid to run a 5140 on anything. Very durable and strong, and a **** of a lot cheaper.

posted January 24, 2004 07:22 AM
i believe the condition of the track has broke more cranks. potholes;ruts;ect. than long or short tracks combined. a well bladed track is a step up in all parts quality. if you race in a pasture get a good crank.

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