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Old 03-27-2012, 07:50 PM
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Changing flywheels?

Ok so I was not sure on where exactly to post this but hopefully someone can help me out here. I have a SBC 385 circle track motor. Externally balanced. We just rebuilt the bottom end over the winter and after getting it all together we decide to get a new clutch. The old clutch was just a junk heavy duty 11' basic clutch setup. Well we went to the 10.5' clutch and it was not until now that I realized that the pressure plate will not bolt onto our current flywheel. It's a old 400 internal balance flywheel. 14 inch diameter. So we need to swap flywheels to the 12 3/4 inch flywheel. The problem is the one we have now is the one that the whole assembly was balanced to. When it was balanced with the current flywheel, the balance plate that bolts between the flywheel and crank was balanced with it. So if we go to a 350 flywheel, what all do we need to do? Sorry for the long post. Just trying to figure it out. Do not want to just throw it on there and waste a motor. Thanks!

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Old 03-27-2012, 10:06 PM
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Last edited by cobalt327; 03-27-2012 at 10:08 PM. Reason: Misread post.
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Old 03-27-2012, 10:39 PM
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Old 03-27-2012, 10:46 PM
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Get new pp to fit flywheel. other option drill fw to fit pp.
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Old 03-28-2012, 08:22 AM
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If it's "an old 400 internal balance flywheel" (huh???), it's NOT "externally balanced". More than likely, if it was balanced as a true "race" engine, it was "converted" to internal and a 350/396 flywheel was used. With an 11" clutch, it was probably from an SS396 (375 HP) or 427 Corvette. Most small blocks I've seen over the years were the 10.4" (10 1/2 in the "vernacular"). Machs nicht...

The best suggestion so far is to have the flywheel modified to accept the smaller plate. Locate an industrial machine shop in your area and ask them to install a new "bolt circle" on the flywheel. It's relatively easy and straight-forward. MAY take 1.5 hours, but probably less. It will have no effect on your balance.

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Old 03-28-2012, 08:50 AM
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Just make sure you have the same hub size matching the crank to the fly-wheel. I know when using a newer gen II block they have a smaller hub on the crank as compared to the older gen I blocks. I wanted to use an older style flywheel because of the 10.4" clutch I'm using. I went to Hays and they had the correct flywheel for me. Just my 2 cents...
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