Re: Off set grinding a cast 440 crank.
[Re: tuff440]
#2804505
08/02/20 11:16 PM
08/02/20 11:16 PM
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Joined: Jan 2003
Posts: 6,148 Melbourne , Australia
LA360
master
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master
Joined: Jan 2003
Posts: 6,148
Melbourne , Australia
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Would offset grinding a cast 440 crank significantly weaken the journals? 2.375" down to 2.200" and adjusting the stroke from 3.75" to 3.91" would reduce the journal overlap by about 25%
or would the chamfered edge and lower rod weight and smaller bearing surface counter the loss of material? Have you spoken with your crankshaft grinder to see if it's possible? Without welding, you'll take 0.020-0.030" or more to get below the undercut, before you can even start start producing a fillet. Start taking off too much and you move the position of the oil holes on the journal.
Alan Jones
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Re: Off set grinding a cast 440 crank.
[Re: polyspheric]
#2804604
08/03/20 10:38 AM
08/03/20 10:38 AM
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Joined: Jan 2003
Posts: 10,012 Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,012
Frostbitefalls MN (Rocky&Bullw...
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The nominal journal overlap width in inches (as calculated by the conventional method) is reduced by 25% (.6875" vs. .5200"). However, GM and engineers use the actual intersecting area in square inches, which is a "lens" rather than a line, to compare stiffness. The math is very annoying (see the actual calculation here: https://mathworld.wolfram.com/Circle-CircleIntersection.html, and my remarks here: http://victorylibrary.com/mopar/journal.htm), but for this example the journal areas are: Stock: .822" Offset: .534" Loss: 35% Spending $$ to offset grind a cast crank would be false economy. Your best bet for a cheap build is use stock replacement parts (rods pistons crank) so you can skip balancing and expensive machine work. If you can find proper compression stock wieght pistons they will handle 500 hp.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Off set grinding a cast 440 crank.
[Re: tuff440]
#2804749
08/03/20 08:18 PM
08/03/20 08:18 PM
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Joined: Jan 2003
Posts: 6,148 Melbourne , Australia
LA360
master
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master
Joined: Jan 2003
Posts: 6,148
Melbourne , Australia
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Alan do you think the reduction in journal overlap would make a big difference in strength. I recently saw photos of a forged 440 crank that was offset ground to 3.85 and used bbc rods and the journals were left with a fillet, maybe some one who has done it can chim in. I'm trying to build a motor with parts I have on the shelf, one of those being some h beam rods with bbc journals. We've all been there, if it's a relatively mild I doubt you'll have a problem. BBC ran a cast crank with a 4" stroke. Whether it's worth the $$$ and effort, that's entirely up to you. You might get lucky and someone who has done it will chime in, but I don't imagine it's been done often. Best of luck
Alan Jones
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Re: Off set grinding a cast 440 crank.
[Re: tuff440]
#2804789
08/03/20 09:54 PM
08/03/20 09:54 PM
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Joined: Jan 2003
Posts: 1,022 Andrews,In. U.S.of A.
67_Satellite
super stock
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super stock
Joined: Jan 2003
Posts: 1,022
Andrews,In. U.S.of A.
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If you really want the inches, you might be better off $$ wise to look for an aftermarket crank which would open up the opportunity for even more c.i.. That being said, I don't think a mild build would break an offset ground cast crank. I run an offset ground forged crank and have had no problems even with boost thrown at it.
Last edited by 67_Satellite; 08/03/20 09:54 PM.
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Re: Off set grinding a cast 440 crank.
[Re: tuff440]
#2804800
08/03/20 10:27 PM
08/03/20 10:27 PM
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Joined: Nov 2015
Posts: 880 Missouri
jwb123
super stock
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super stock
Joined: Nov 2015
Posts: 880
Missouri
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Just asking but with all the cheap forged stroker kits available, why would you want to mess with offset grinding a cast crank? 440 source has kits with everything to assemble a short block for $2,300.00 If you offset grind a crank you still need bearings, rings, balancing, longer rods, and or different pistons. Add it all up, and take into consideration you are getting forged parts, instead of cast, and the kit looks pretty cost effective to me. Trust me I ponder all kinds of ways to fabricate cheap stuff to go racing, but with the price of kits, that is the cheapest dependable route.
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Re: Off set grinding a cast 440 crank.
[Re: LA360]
#2804841
08/04/20 02:24 AM
08/04/20 02:24 AM
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Joined: Aug 2003
Posts: 43,252 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,252
Bend,OR USA
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Is your crank going to be weaker? Yes
Is it going to matter in your application? Probably not Now can you afford the cost and failure if it doesn't stand up? I'm thinking Ma Mopar made all their BB cast cranks out of steel, not cast iron
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Off set grinding a cast 440 crank.
[Re: tuff440]
#2804888
08/04/20 09:17 AM
08/04/20 09:17 AM
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Joined: Nov 2015
Posts: 880 Missouri
jwb123
super stock
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super stock
Joined: Nov 2015
Posts: 880
Missouri
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I'm not looking to build a cheap motor, just want to use parts I already have and buy what I need. Only looking for 450-500hp and its a driver not a racer. Sure a forged crank would be better but I'm sick of seeing stuff gathering dust when it could be used. Like I said earlier, I have some rods that have 2.2 journals and are stock rb length, just need some new light weight forged pistons. jwb123 that 440 source kit at $2300us will end up being over $5000 once landed in Australia. Honestly the cost of offset grinding a cast crank doesn't bother me, its whether the cranks strength has been comprised that concerns me. WOW! I did not notice you were from down under. The duty increase really sucks. They did build a lot of 440's with forged cranks, I think if you can find one I would use that. Heck I tossed a couple 440 cranks the other day cleaning the shop. Nobody wants a stock crank that needs to be turned anymore. The offset grinding was something we did 40 years ago due to no cheap cranks available. I guess with the prices in your country, you are where we were 40 years ago. In my neck of the woods I don't think there is a machine shop I would trust to do the offset grinding, all the guys that did it, retired or closed shop, all the shops that can still do it would charge more than a new crank would cost. My hat is off to you for trying to do it the old school way.
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