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Old 08-18-2008, 05:12 PM
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Internal vs External Balanced 396/427

Hey Guys,
I am still not totally educated on internal balanced
vs external balance. I know the 454 has the big harmonic
balancer and the 396 & 427 has the small one. Plus when you buy
a flywheel it has to be 396/427 specific. As long as I have my rods,
pistons, crank balanced and I run the right balancer and flywheel I should be good to go??? Rule of thumb is 396's & 427's are internally balanced and
454's are exteranl??? or do I have it backwards?? I have the early 3855962
396/427 block. Apparently on this casting there is enough meat to punch
her out to the right bore for a 427. This block is very rare and want to do it
right the first time.
Any and all info would be greatly appreciated.
Thanks

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Old 08-18-2008, 05:15 PM
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"396's & 427's are internally balanced and
454's are external"

Yes...that is true.
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Old 08-18-2008, 05:17 PM
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396/427 balance.

thanks poncho62
so what happens if a guy puts a 454 flywheel on a 396/427?
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Old 08-18-2008, 05:25 PM
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You'll get a vibration due to imbalance. Do you already have a 454 flywheel? And are you talking flywheel or flexplate?
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Old 08-18-2008, 05:28 PM
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396/427 balance

techinspector tHank you
I do not have a 454 flywheel. I found this 3855962
block and am going to build it for my 65 Malibu. I found
a 427 forged crank to start off. I am going to buy a 396
flywheel for my muncie off of "Ground up"
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Old 08-19-2008, 08:15 AM
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You can put any internally or "neutral" balanced flywheel and flexplate on your 396 or 427. Since all the balancing is done on the crankshaft by adding or removing weight.

The benefit of internal balancing is that if you have a problem with your flexplate, flywheel, or dampner then you can replace it with any other "neutral" part.

If you replace these items on an externally balanced rotating assembly then the new parts have to match the balance of the old parts.

This can be difficult if you break teeth of the starter ring, or if rubber comes out of the dampner or the outer ring of the dampner shifts the balance will be way off and you will have to have the entire assembly done again. Unless you have the balance card.
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Old 08-19-2008, 12:58 PM
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You are building an engine the expensive way. part by part. I did that same thing 25 years ago and swear i would never make that same mistake again.

I recommend that you buy a complete 454 with a set of 781 or 049 heads. Complete with all the tin and pulleys and brackets. Bore it to a 468 cid and install the right pistons to make the compression that matches the cam and gear and stall to be used. A 468 will make more power than a 427 with the same setup (cr, cam, heads, ect). If you have a few more dollars to spend then consider making a 496 cid with a stroker kit.

what kind of build are you planning. street engine, street/strip, strip only?
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