Lightening a stock 440 crank

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cnantz

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I am planning to do some grinding and cleaning up on a stock crank. I don’t wanna remove so much that Mallory needs to be added but will do some weighing and comparing of stock vs the rods, pistons, rings, rod bearings, pins I’ll be running. Question..... when chamfering oil holes how aggressive should a person get? Length of chamfer? How much to chamfer the leading edge vs the trailing edge of the oil hole? What’s your experience?
 
cnantz said:
I am planning to do some grinding and cleaning up on a stock crank. I don’t wanna remove so much that Mallory needs to be added but will do some weighing and comparing of stock vs the rods, pistons, rings, rod bearings, pins I’ll be running. Question..... when chamfering oil holes how aggressive should a person get? Length of chamfer? How much to chamfer the leading edge vs the trailing edge of the oil hole? What’s your experience?
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Just how are you going to be "grinding" on this thing? Are you doing this yourself or paying someone?
 
well I was planning on using a die grinder with a few carbide burrs, file and a 4 inch grinder. When chamfering the oiling holes I was gonna use a stone or maybe a sanding roll/tootsie roll. I’m not going to grind the mains nor rod journals. If that is what your thinking. Just going to remove a little excess material in uncrucial spots, radius and lighten the counter weights. I figure if the machine shop is going to have to balance it by drill holes deeper I might as well remove material before it gets to the machine shop. However I mainly am concerned with chamfering the oil holes. How “big” To make them?
 
I had a guy with a laithe turn down the counter weights on my 440 crank.120 thou. If u don’t turn the weights down u will be drilling big holes in the crank. My thoughts were if I didn’t get enough metal taken off the weights that I would knife edge them some. My Molnar rods and Diamond pistons are a lot lighter. I would check with the guy turning ur crank how much to chamfer the oil holes or even if he recommends it. Kim
 
Chamfer is not critical dimensions, just knock the edges off the hole with a 45 countersink. you really need to get the rods and pistons weighed on a crank balancer to assay how much you can remove. AND all the weights are critically dimensioned from the throws. Its a balancing act on removing weight and then adding mallory in the end at $70 a slug. Id let the crank shop do it on their drill press as your going to get it balanced anyway.
 
My pistons were super light (500 grams) so we turned down the counterweights. They took too much off and had to add $300.00 of Mallory!
 
qkcuda said:
My pistons were super light (500 grams) so we turned down the counterweights. They took too much off and had to add $300.00 of Mallory!
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Why not weld some nice beads on those undersize counterweights and save most of that mallory money?
 
Oil passages, just a light chamfer, gentle touch there. With the angle grinder, it's all knife edging and grinding out parting lines and sharp edges. Again, gentle touch unless you're sending it out to be turned, an "opps" gets expensive fast.

Remember that bobweight is like torque; the greater the working radius, the more effective it is. Removing weight with a lathe is very effective, it's at maximum radius. Grinding and knife edging doesn't give as great a return, since you're working at reduced radius. So if you remove say 400gm of actual metal, it won't have nearly 400gm of bobweight reduction, depending on where the metal was taken from. S/F....Ken M
 
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