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GMC V6 and V12 Engines Engine repair and rebuilding

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  #11  
Old October 13th, 2023, 04:31 AM
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Funky61 Funky61 is offline
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Default Re: Locking Tabs 4 Flywheel?

From the Archives Previous Forum Posts...

Quote:
The 478 was introduced in 1962 in the 6500 and 7500 series trucks, later in some 8500 series trucks. This included Conventional cab, tilt cab and rear engine buses. By the early 70's it was available only in the 7500 series, 74 being the last year of production for all GMC's V6 engines. They actually introduced two new displacements in 73 which were a 379 and 432. Basically GMC took the 351 and 401 and increased the stroke from 3.58 to 3.86 which is the same stroke as a 478's. If you really want to go with the 478 keep in mind that this engine is also externally balanced and you'll need a custom flywheel to fit the lighter duty application. I had Tilton Engineering fabricate one for the cost of $1100. Then had the crank, flywheel, and front hub and pulley from my 305E balanced as one assembly. A lot of weight was added to the crank but it still needed some on the flywheel and front pulley for proper counterbalance.
305,351and 401 engines are fully internally balanced and flywheels are interchangeable with just these three. 478's have 8 bolts holding the flywheel to the crank, 305, 351,401 have the standard 6
like most passenger car and light duty truck GM engines. What I'm trying to say is a 401 will be alot easier to install and much less expensive. But if you're like me and are very committed to such an idea like this then go for it. To me it was a childhood dream when I was 15 years old, about 21 years later I decided to finally to it. There's a wrecking yard in Ohio called Sam Winer Motors that has 351, 401 and 478 V6's, when I'LL find the phone number I will E-Mail it to you. I'LL be glad to help you with any other information whenever you decide to do such a conversion. Pete.
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  #12  
Old October 14th, 2023, 03:20 AM
Mulana Mulana is offline
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Default Re: Locking Tabs 4 Flywheel?

A lot of good historical information there... thank you!

After checking out the web and the 6066 site in particular, I excitedly purchased a 432 about three years ago from a truck parts yard. This particular motor was "rebuilt" and sat for many years on a shelf indoors. When I got it, a roof leak sent water into one of the cylinders. Anyhow, the motor has been completely gone through needing only a power-hone in one cylinder, rings, cam bearings, valve surfacing, and all the gaskets. I had issues with the flywheel as stated in a previous thread and purchased what I thought was a 401 wheel. Currently, I am using a 351 flywheel-housing, and a 5-speed transmission. I may or may not use a splitter, bit it is all going into a 1962 one-ton unit with 18-inch wheels. The intake manifold has a date stamp of 1971, but manifolds can easily be swapped out.

With all the great help I am getting from the 6066 brothers and sisters (THANK YOU ALL), it sounds quite bit like what I thought was a 401 flywheel is actually some other 8 bolt GMC V6 wheel. In either case, the wheel, front counterbalance, and the crank have all been balanced as one unit. The motor sits in a cradle waiting to come to life soon. Just a couple of things left to do when time permits. In the meantime, the kids here at the high school are eyeballing the motor and asking many questions. They frequently stop by the 5-sp and shift through the gears. It doesn't take much to enthuse the kids.... they are as excited as I am.

Last edited by Mulana; October 14th, 2023 at 05:41 PM. Reason: I wanted to thank my 6066 brothers and sisters for all their help thus far.
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  #13  
Old October 19th, 2023, 05:10 PM
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Default Re: Locking Tabs 4 Flywheel?

Jim:
Yes 305 and 351 flywheel is interchangeable. I reused my 305 flywheel when I upgraded to a 351e via a rebuilt long block that I purchased.

Hope that helps.
Regards
Steve
New Orleans
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  #14  
Old October 20th, 2023, 01:00 PM
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Default Re: Locking Tabs 4 Flywheel?

In my 305, I know that these lock tabs and slightly different is center of hole dimensions, they will only fit on one way. I happen to have a shot of mine when I was reassembling the old hydramatic.
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  #15  
Old October 21st, 2023, 05:15 AM
Mulana Mulana is offline
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Default Re: Locking Tabs 4 Flywheel?

Steve: Thanks for your response... this saves me a bunch of time!

My next step now is to finalize a Fusion-360 drawing and send it to Send-Cut-Send, and have them laser cut me some new flywheel tabs. I am planning to have some six-and eight-hole tabs made and hand them out at cost if anyone is interested.

Stay-tuned
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  #16  
Old October 21st, 2023, 05:17 AM
Mulana Mulana is offline
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Default Re: Locking Tabs 4 Flywheel?

Jbgroby: Thanks for the picture. Nice motor by the way! I can clearly see the ring-tab and the identifier hole. This helps me out.
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