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Old 06-27-2011, 11:01 PM   #1 (permalink)
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Default 6g75 crank swap

How hard is it to change the crankshaft in a motor? I am very mechanically inclined, but this is going to be my first time pulling a motor apart. My motor spun a bearing and I'm planning to change the pistons, rods and crank. I figure if I'm putting a new crank in, I might as well go with the 6g75 instead of the 6g74. Will the stock 6g72TT ECU adjust for the larger displacement and different crank or am I definitely going to need a standalone AEM EMS?
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Old 06-27-2011, 11:24 PM   #2 (permalink)
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Default Re: 6g75 crank swap

Won't fit...

You can make a 6G74 crank fit with over $1k worth of machine work...
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Old 06-27-2011, 11:33 PM   #3 (permalink)
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Default Re: 6g75 crank swap

You can only fit a 6G75 crank in a 74 motor. The 72 motor will take a 74 crank but with modification and tons of money. A stroker short block is $6500. If you do it yourself you can probably keep it to $4k. I have a block that can get you started. It's already clearanced to fit a 6G74 crank.
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Old 06-28-2011, 04:06 PM   #4 (permalink)
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Default Re: 6g75 crank swap

I didn't know you guy's were paying that much. I can get a crank ground to any size i want for $100-$250, and grinding the block and girdle is easily done at home, or a couple of hours at $100 an hour shop time.
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Old 06-28-2011, 04:13 PM   #5 (permalink)
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Default Re: 6g75 crank swap

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Originally Posted by donniekak View Post
I didn't know you guy's were paying that much. I can get a crank ground to any size i want for $100-$250, and grinding the block and girdle is easily done at home, or a couple of hours at $100 an hour shop time.
It's having the counterweights machined down and the Mallory metal added that costs the big bucks...
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Old 06-28-2011, 04:22 PM   #6 (permalink)
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Default Re: 6g75 crank swap

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Originally Posted by donniekak View Post
I didn't know you guy's were paying that much. I can get a crank ground to any size i want for $100-$250, and grinding the block and girdle is easily done at home, or a couple of hours at $100 an hour shop time.
Ray does the machine work to the rod mains, center mains, and counterweight cutting. Cost for the proper machine work and balancing for a 74/72 stroker crank is around $1600-1650...?... I think.
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Old 06-28-2011, 04:36 PM   #7 (permalink)
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Default Re: 6g75 crank swap

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It's having the counterweights machined down and the Mallory metal added that costs the big bucks...
I know, i get 4g6x cranks worked all the time. It's not to much to have anything turned down on the lathe, and balancing is only $100. I was looking into doing this in my car, but could only find 2-bolt block cores at the time. That, and the longer the stroke, the more the inherent oiling design flaw in mitsu cranks rears it's ugly head.
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Old 06-28-2011, 06:24 PM   #8 (permalink)
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Default Re: 6g75 crank swap

My motor is a 6g74 that I want to put a 6g75 crank in. Is it just a matter of swapping it out or will I have to worry about balancing it or messing with the timing?
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Old 06-28-2011, 11:35 PM   #9 (permalink)
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Default Re: 6g75 crank swap

Quote:
Originally Posted by 1992redvr-4 View Post
Ray does the machine work to the rod mains, center mains, and counterweight cutting. Cost for the proper machine work and balancing for a 74/72 stroker crank is around $1600-1650...?... I think.
It's $1600. That's what I paid. Like $900 for the machine work and the rest was for the balancing. Mallory is very expensive. The weights are also punched in through the side of the counterweight not drilling and stuck in the ends.

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Originally Posted by bochicchio.mike View Post
My motor is a 6g74 that I want to put a 6g75 crank in. Is it just a matter of swapping it out or will I have to worry about balancing it or messing with the timing?
You'll have to balance it because you need to get custom pistons. The crank fits fine with no machine work. You can use 6G74 rods too. The piston pin location is moved up towards the top of the piston because of the extra stroke.
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Old 07-05-2011, 12:01 AM   #10 (permalink)
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Default Re: 6g75 crank swap

So I'll have to send my motor out to get balanced after I put the pistons in it?
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