Forged steel 340 crank

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Captainkirk

Captainkirk

Old School Mopar Warrior
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Wednesday I "intercepted" my crank from the machine shop. It's been degreased and ground .010 under and is awaiting balancing and chamfering of the oil holes, but here's the thing; This crank, while being forged, and thus highly desirable, is really sloppy. There is forging flash all over the thing, sharp edges, and very rough counterweights (on the sides). My purpose in "intercepting" it is to clean all this up with a carbide bit, files, Roloc discs and whatever else will work. Note this will be done only on the rough forged areas; I'm leaving the machines surfaces and journals for the pros. My question to any racers or pro builders out there is; how carried away should I get? I realize the smoother the crank, the less oil drag will be generated, but am I making this a bigger deal than it really is?
The cast crank I took out, while metallurgically inferior, is a much "cleaner" piece........

I've attached a pic of the crank before it went in for grinding.........

crank 340.jpg
 
Hello Kirk
I wouldn't get too carried away, you could take it out of balance(unless you are going to rebalance it).
Every little bit you grind off probably will affect the balance.
Good luck Dave C.
 
Thanks for the speedy reply!!!!
That's why I "intercepted" it; it HAS to be balanced as it's out of a different motor, and I wanted to do all my grinding and cleanup BEFORE the balance. I'm using this crank, damper and flywheel ('69 340) with the original block, pistons and rods out of this motor ('72 340)
BTW; my machinist INSISTS on balancing the crank, rods, pistons WITH new rings and bearings in place to get everything just so....nothing wrong with perfection, huh?
PS- Interested in a manifold for your 273? If so, check out my description in the parts for sale section
 
Do you have another pic of that crank, maybe one of the rod journal area. It seems too smooth to be a forging, although it's hard to tell from just that one pic.
 
I would not remove too much material, when I had my crank balanced it came up that material needed to be added to balance it which increased the cost maybe not the case with your machinist but worth asking.
 
Well, I've ground off the most heinous forging flash.....hope I didn't grind too much....now it'll go back to the machinist to see if a) I can grind/ smooth some more, and b) if I screwed it up (LOL) I'm comfortable with it now if I can't grind anymore; there are no more stillettos sticking out waiting to nip off an errant finger; but there's a lot more that could be done to it. I'll keep y'all posted.

crank1.jpg


crank2.jpg


crank3.jpg
 
Sorry Captain, that is definately a forged crank, the first pic looked a lot like a casting! What piston/rod combo are you running, if the pistons are lighter than factory ones you shouldn't get into trouble lightening the crank here and there.
 
I'm running stock rods with TRW forged 13:1 pistons....not sure of the P/N on the pistons as they're at the shop still, but "these are them".

TRWs.jpg
 
You shouldn't have any balancing problems, most of the weight you have taken off the crank is around the rod journal area. I knife edged my small block crank and still had weight taken out of the counterweight area when it was balanced but I am running a fairly light set of Ross pistons.
Those big block cranks are certainly pretty rough, there's a lot of tidying up you can do.
 
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