4.0 with 4.2 rods and crank

[thejim42]

have an extra motor that needs to be rebuilt sitting on my garage floor and was doing some research on what kinds of things i can do to it. Does anyone have any information on using the 4.2 crank and rods in a 4.0. from what ive read it strokes the engine to a 4.5 or 4.6. Has anyone done this? Was planning on get a master rebuild kit with new pistons, having the block bored .030 over, and getting a new crank and cam anyway.

[cruiser54]

Dino Sava has a great site covering all of this.

 

Google "poor man's stroker".

[HOrnbrod]

Start reading HERE in the FAQS section. All you need to know.

[Eagle]

Many, many people have done this.

 

What you need to be aware of is that there is a slight difference in deck height between the 4.0L and 4.2L engines. If you do the "budget stroker" using stock 4.2L connecting rods, using OEM replacement pistons results in a bump in compression ratio that usually causes detonation problems. At least one of the companies that sold shop-built stroker engines used 4.0L rods with custom pistons. Other people deal with it by doing things like polishing and enlarging the combustion chambers in the head, and running a cam with enough overlap to effectively lower the compression. I remember at least one person who ran two head gaskets to decrease the compression -- but I don't recall how long that held together.

 

By all means, spend a lot of time reading Dino's web site. Zero in on discussions of "quench."