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Discussion Starter #1
i have a brand new 427 tall deck , and ive been lookin at cranks and just shoppin around , and ive been able to come across a forged 4.25 crank pretty cheap brand new ... i was originally thinking of a regular 427 or even a 4.00 stroke....but for the stroker crank price im thinkin about buyin it .....BUT my question is , what needs to be done to the block to accept a 4.25 crank? ive read that another oil pan , and notching the block? as far as what im building it for is 70% strip and 30% street
 

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A 4.25 crank will fit with little or no block mods if you use the correct rod/piston combo.

At present I have a 4.25 crank with 6.385 Eagle style rods and flat top blower pistons in a short deck. Nothing even close to hit.

I am building the same combo in a tall deck with longer aluminum rods but, they hit the bottom of the cyls. Only because of the aluminum rods.

I only get into real bad fit problems with the 4.375 and 4.500 cranks.
 

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1967 Chevrolet Biscayne 10-71 blown 433 Big Block Chevy, T400 & 12 bolt 3.73 rearend
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A 4.25 crank will fit with little or no block mods if you use the correct rod/piston combo.
I have built quite a few of these engines. What Bob says is right on. In some cases, if you use a cheap crank, the counterweights will make contact with the block, but this is rare. I would run the +.400 rod with this combination for a better R/S ratio.
 

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Discussion Starter #4
6.385 Eagle style rod
explain to me , for example the 427 came with ....6.135 rods? then you mensioned 6.385 rods , ive heard of longer rods being prone to breaking , anywho what would be the outcome for example a 4.25 stroke with shorter rods?
 
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