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post #1 of 2 (permalink) Old 11-29-08, 03:45 AM Thread Starter
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confused 390 to 428

I want to convert a 390 over to a 428. What do I need to know? Thanks

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post #2 of 2 (permalink) Old 11-29-08, 06:14 AM
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Re: 390 to 428

If you can find a 428 block that would be better....Two things right off the bat...bore the cylinders from the 4.050 (390 bore) to a 4.130 (428 bore) if your block is in good shape it'll take to the .080 thousandths over bore....you then need to find a 3.98 stroke crank. It'll have a 1U on the seventh counterweight. finding this crank can get expensive $400 - $600 on the average, you can look on ebay or if your trying to save money, look in your local junk yard. I doubt you'll find any 428's, but look in the old mercury section they made a 410 cid which was equiped with a 1U 428 crank.

Once you have that done it's all gravy

Also if you want it to flow good use tall port heads....the 390 volocity heads are OK but not enough...in my opinion. Your 390 heads if they are old GT heads may already be tall port.

Last edited by kdtrucker; 11-29-08 at 06:16 AM. Reason: mispelling
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