Unbalanced ? - Ford Muscle Forums : Ford Muscle Cars Tech Forum
 
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post #1 of 4 (permalink) Old 05-17-2013, 08:57 AM Thread Starter
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Unbalanced ?

Just bought a 69 highboy with a 428 in it and I'm feeling a vibration in the drive line starting at about 1500 rpm and more pronounced when the engine is under load. With more research I've discovered the recently built 428 is actually a 352 punched out with 428 pistons, con rods and crank. It's got a four speed manual installed but after inspecting the flywheel I've determined that a neutrally balanced flywheel was installed by the previous owner. I've also found out that the builder wasn't supplied with the flex plate or flywheel to balance the rotating mass as a unit. Will not the 428 crank require a externally balanced fly wheel now as opposed to the internally balanced 352 set up ?
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post #2 of 4 (permalink) Old 05-17-2013, 09:16 AM
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Re: Unbalanced ?

You sir are MISTAKEN.


There are only TWO 352 Blocks in the ENTIRE WORLD that can be bored out from 4.0 to 4.13, and the one in your Truck is NOT one of them in my opinion. There are some 390's that can take it which is most likely what you have.

Yes the 428 is Externally balanced. Eagle makes an crank that don't require external balancing for the 428.
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post #3 of 4 (permalink) Old 05-18-2013, 08:29 PM Thread Starter
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Re: Unbalanced ?

Thanks for the reply, being a new comer to FORD I can only take the word of the previous owner till I get up to speed. I'm assuming this engine, what ever it is, has a 428 crank...How do I verify that and how do I tell if it's a internally or externally balanced crank ? I've got a vibration that starts coming on at 1500 rpm's and a rear seal leak that's getting worse. Clutch engaged or disengaged no difference. I'm leary to run this truck till I determine for sure what's in it, balanced or unbalanced.
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post #4 of 4 (permalink) Old 05-19-2013, 12:00 AM
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Re: Unbalanced ?

Veryfy a 428 crank by a down inserted into a plug hole... 3.98 Stroke is the 428 crank. measure it.

The crank on the first throw will have a U-2 part stamped into it I believe...
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