4.2 crank in 3.8 what need to be done?

92tbird04

Registered User
Its been a while since I had a sc. Just picked up a 89 with a spun rod bearing. I'm looking in to the 4.2 crank swap. Was wondering if it a direct swap using the rods from the 4.2 or if there is machining required? And if the balance of the 4.2 crank needs to be done. Any insight or suggestions would help.
 
A few guys on here have done this (Niebert and Roadhawg come to mind) and maybe they'll chime in here. Until then, at a minimum you'll need 4.2L crank, rods and pistons. They 4.2 is zero balanced like the SC, so your crankshaft damper and flexplate/flywheel should work. Here's also some reading that may be helpful: http://www.v6power.net/vb/showthread.php?t=8310
 
I just changed out rods and crank on a 3.8.

Balancing was flex, crank, rods, pistons, rings, pins, bearings and HB.

In case it breaks eveything interchanges to the chart except the pins.

Paul
 
I used a new 4.2L crankshaft from Ford. I used a standard size bearings for a 4.2L, as the rear bearing is not undersized like the forged SC 3.8L crankshaft. One of the Main bearing tangs will not line up. You will need to remove the tang from the bearing or modify the notch in the maincap. I chose to modify the maincap. I used SCAT 6.125 connecting rods and a set of custom forged pistons. I used a Marauder Flex plate and a 94/95 SC balancer. Then have the rotating assemble balanced.

6pack.jpg
 
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