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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old October 3rd, 2023, 02:54 AM
Mulana Mulana is offline
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Default Locking Tabs 4 Flywheel?

Hey All: I'm looking for the flywheel tabs for my 432V6. I believe they are tempered and not meant to fold around the flywheel bolts. Anybody know of a source?

Thanks, Jim.
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  #2  
Old October 5th, 2023, 07:21 AM
Prowbar Prowbar is offline
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Default Re: Locking Tabs 4 Flywheel?

You are correct that they are made from hardened steel and do not fold around the bolts. I assume you have an 8-bolt flywheel and crankshaft?

Possibly another member has a set lying around? Otherwise, they could be laser cut or waterjetted from a piece of spring steel.
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  #3  
Old October 7th, 2023, 01:39 AM
Mulana Mulana is offline
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Default Re: Locking Tabs 4 Flywheel?

Excellent idea... that didn't occur to me. Send-Cut-Send will probably be able to make them for me. Might as well produce extras in both the six- and eight-lug patterns.

Thank you for responding.
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Old October 7th, 2023, 07:44 PM
Prowbar Prowbar is offline
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Default Re: Locking Tabs 4 Flywheel?

Good luck. Don't have a picture of one, unfortunately. They are rectangular plates, about .080" thick, and have a radius cut out where they mount to the center of the flywheel to provide clearance.
Do keep in mind that one of the eight (in the case of eight bolt flywheels) has a different (shorter) C-C hole distance, so the flywheel can only go one way due to the external balance. The difference is minute but there. These have a small hole in the center of the plates to identify them as such.
The 6 bolt flywheels are all the same, no external balance on those.
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Old October 8th, 2023, 06:28 PM
Mulana Mulana is offline
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Default Re: Locking Tabs 4 Flywheel?

Prowbar: I'm not sure if my response to your reply made it or not, so I am trying again:

Yes, you are correct about the offset on the big crank flywheels. I have measured out everything directly off the crankshaft of my 432 and will have a mild-steel version cut out first to make sure the dimensions are correct. If they are, I will have the hardened steel versions cut in the shape of a ring for simplicity instead of individual tabs.

I measured my six-lug flywheel tabs, and they are .060 in thickness.

Do you know if the 305's and the 351's use the same flywheel bolt pattern? I am measuring an offset on my 351 flywheel. I have all three tabs for the 351, and they are not the same. As you mentioned with the 478 tabs, one of the 351 tabs has an identifier hole in it to separate it from the rest.

Thanks again for your quick replies, Jim Mx.
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Old October 9th, 2023, 07:35 AM
Prowbar Prowbar is offline
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Default Re: Locking Tabs 4 Flywheel?

The idea of a ring instead of individual tabs is a great improvement. I never measured my locking plates, the .080" was a guess, you're correct about the .060" thickness.

I believe all 6 bolt cranks use the same pattern. If the flywheel is zero balance, ie. no added offset weight cast into the flywheel, the bolt pattern should be symmetrical. That is my assumption.

I checked this but will recheck this tonight on my 305 to be sure.
The 305, 351, and 401 are all internally balanced, so the flywheels should swap over without issue.

Hope we can get this sorted out.
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Old October 9th, 2023, 06:17 PM
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Default Re: Locking Tabs 4 Flywheel?

My 401 only had two of those tab plates and the other two bolts someone added lock washers.

So one tab has a center-hole and they are spaced differently. When overlayed you can see the offset.

The Automatic transmission adapter uses a ring.
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  #8  
Old October 9th, 2023, 09:44 PM
Prowbar Prowbar is offline
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Default Re: Locking Tabs 4 Flywheel?

Checked my 305 and it also has one locking tab with a hole! Did not remove it. Seems like the 6 bolt flywheels have an asymetrical bolt pattern as well!
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Old October 11th, 2023, 01:37 AM
Mulana Mulana is offline
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Default Re: Locking Tabs 4 Flywheel?

The flywheel I am using on my 432 is a 401 wheel. I was not having much luck finding a good 432/478 wheel, so I had the 401 rebalanced. The 401 wheel I bought from another 6066 brother is an 8-bolt pattern.

The 351 flywheel I have is giving me fits for accuracy since it is so worn out. When the rains let up (har!), I will go to my local truck wrecking yard that have several 351's, etc. and get me some measurements right off the crankshaft.

Stay tuned!
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Old October 13th, 2023, 02:20 AM
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Default Re: Locking Tabs 4 Flywheel?

I have measured the degrees on an indexing head used in a machine shop, and this is what I have thus far:

The 379, 401, 432, & 478 flywheels have eight holes on a four-inch circle. The bolt holes are spaced out at 45 degrees except for one that is only 2 degrees offset.

The 351 flywheel has six holes on a four-inch circle. The bolts are spaced out at 60 degrees except for one that is offset by only 2 degrees.

My last task is to find a 305 crank/flywheel to measure. If anyone knows if the 305 and 351 flywheels are interchangeable, that will save me some time.

Off and running, Jim Mx.
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