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343 crank with 6cylinder flywheel

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myrambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Topic: 343 crank with 6cylinder flywheel
    Posted: Jan/17/2018 at 11:35pm
Does any one know where I can locate an adapter ring so I can install a 6 cylinder flywheel on my 343 engine? I assume this would be a ring that fills in the space between the 4.5 343 crank flange and the 4.65 recess in the flywheel. A recent 343 engine purchase came with a 6 cylinder flywheel and I was told it was mounted on this engine however no spacer came with it. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2018 at 8:22am
IT might very well mount without such a spacer. You will have to check starter engagement if clearances are good, but I suspect 0.15" won't make a noticeable difference. Note that six cylinder flywheels are neutral balance, so it will either have to be balanced to the engine or the engine internally balanced. If engine isn't internally balanced I'd order the appropriate 360 flywheel.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2018 at 5:02pm
I appreciate the input. This is however a 343 crankshaft, not a 360 crankshaft so a 360 flywheel will do me no good unless it was from a 70-72 flat crankshaft engine, and then I would still need to have weight removed to balance to my engine.  The 6 cylinder flywheel will bolt up however then it is not exactly centered as there is a little play in the bolt holes plus then all the force is on the bolts vs being supported and centered on the end of the crankshaft. I was told it was mounted to this engine in a running jeep so I assume it was already balanced with the engine assembly. There are a few posts I have seen where a spacer ring is used when this has been done. I just need to find one, or hope someone that has done this can offer a source or perhaps someone has one they would be willing to part with. My other option is to purchase an original 343 flywheel or aftermarket one if they are available. (which is what I thought I was getting when I purchased this engine Ouch) Discovered it was a 6 cylinder flywheel after getting it home and checking numbers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2018 at 5:21pm
I wonder if bolts with thicker shanks could be found/ordered to center the flywheel on the bolt holes with less/no play?

Checking the flywheel for runout afterwards to verify the fix could be done at home.

Any raised shank bolt of the appropriate thread and length could be made to work,
the holes in the flywheel could be opened up if the shanks were too big,
or you could have bushings made if the shanks were too small.

You could also redrill the flywheel a few degrees off from the original pattern, since a L6 flywheel is neutral balanced.

Other options would be to have the register on the flywheel slightly opened up, and have a ring machined to make up the difference pressed into it.

Im sure any decent machine shop would have some good ideas to make it work,
but I would want to try to verify that the engine was neutral-internally ballanced before investing in adapting the later flywheel.
71 P-code 4spd Javelin/AMX
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lyle Quote  Post ReplyReply Direct Link To This Post Posted: Jan/18/2018 at 5:27pm
That spacer is a custom machined part as far as I have searched on the AMC and Jeep forums.
If the engine was running with that flywheel then the spacer would be neutral to balance.
If you buy a flywheel for the 343 and have it match balanced to the I6 flywheel you have, then all should be good, and it's likely cheaper then having a custom spacer made.
Also better in the long run having the right part for the motor.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2018 at 1:45pm
Here is a picture of the kit.  It spaces the transmission off of the engine 1/4"
The part number is 601-0110.  I will try to find out who the vendor is.
IMG_4014 by Rick Jones, on Flickr
I found this in my search from Fran's site:
 They also list an adaptor for billet flexplates including BW type. This adaptor is to use them for "street use" and is not the adaptor that people use to mix and match transmissions with various year cranks.
 Their site is www.amclives.com. The number from the catalogue is:321-632-8299- don't know if that is current. The part number for the adaptor is:601-0110



Edited by SC397 - Jan/20/2018 at 2:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2018 at 2:47pm
Just saw your entire post. Thanks I'll check it out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2018 at 3:03pm
Thanks for the picture and info. I was thinking the adapter would be a small spacer around the perimeter of the flat crank. Does this change what manual transmission can be used?
Is there any visual way to look at the crank to see the engine has been internally balanced to use the neutral balance flywheel? Or would they have done something to this flywheel? I guess what I'm saying is since I was told by PO and the PO told him this flywheel was used on the engine I'd like to verify it indeed will work before going to the trouble of the kit. The flywheel was sold to PO not attached to the engine and was marked with chalk 343, he assumed as I did when purchasing the engine that it indeed was used with this engine.
If not I'd be better off finding a 343 flywheel. Any thoughts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2018 at 3:09pm
How is this kit different from the one used to upgrade an automatic transmission to the early crank?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SC397 Quote  Post ReplyReply Direct Link To This Post Posted: Jan/20/2018 at 3:41pm
The kit adapts a late flywheel or flex plate to the early crank. 
It is the same kit that adapts the late transmission to the early crank.
It spaces whatever AMC transmission you are using 1/4" back. 
With using a manual transmission, you might want to have a 1/4" longer pilot bushing machined up.
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