4.2l crank modification

damontis

Registered User
Ive read that when using the 4.2 crank, you need to modify it to fit in the sc block. I have a 2002 block from an f-150 and want to know how to modify the crank to fit in my 3.8 sc block.
I have also heard that the rods in the f-150 are weak, so i was going to use my sc rods if they are still good, along with the pistons. is this possible and/or what other possibilities and problems do i face?

or should i just use the 4.2l block and bolt the sc stuff to it?
 
Ive read that when using the 4.2 crank, you need to modify it to fit in the sc block. I have a 2002 block from an f-150 and want to know how to modify the crank to fit in my 3.8 sc block.
I have also heard that the rods in the f-150 are weak, so i was going to use my sc rods if they are still good, along with the pistons. is this possible and/or what other possibilities and problems do i face?

or should i just use the 4.2l block and bolt the sc stuff to it?

There are no mods required on the 4.2L crank. Depending on what year block you are using you may have to modify a bearing to match the notches in the block.

The 4.2L rods are weak but you can't just use SC rods as they will cause the piston pins to hit the counterweights. Some people have had the crank machined down to clear the pins or else you can use aftermarket longer rods. Either way you'll need custom pistons and you'll have to rebalance the crank.

Using the 4.2L motor leads to a few other problems as well. If your SC is 89-93 then the crank sensor won't bolt on causing issues with that.

None of this is insurmountable but it's not a direct bolt in no matter how you look at it.
 
so my best option being the fact that my motor is a 91, is to use the 4.2l crank and get rods and pistons for the crank and then have it balanced. If i do this, will i still need to balance the motor?
 
so my best option being the fact that my motor is a 91, is to use the 4.2l crank and get rods and pistons for the crank and then have it balanced. If i do this, will i still need to balance the motor?

Not sure what you mean by this. You'll have to balance the crank, which you already mentioned, not sure what else you mean.
 
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