[dan_yoyo]

Good day,

I am doing a 4.0 head (7021) and MPI (94’ 4.0) swap onto my 4.2. My first question is what are the main differences between the 4.0 and 4.2 block, I mean besides some water ports and fuel pumps?

Now for my 4.0 head, I am going to install roller rockers, so which pushrods should I be using.....4.0, 4.2 or does it matter? The extra water ports have been sealed.

On to the block, are the cams different in the 4.0 and the 4.2? I want to put in a mild cam and replace the lifters with a hydraulic set, so should I go with (again) 4.0 or 4.2 parts or does it matter?

Water pump, Will a 4.0 water pump fit on the 4.2 block?

I guess the reason I’m asking is it seems there are many more options for the 4.0 and I don’t like limiting my options!

Any input would be greatly appriciated!!

Thanks,
Dan

[dan_yoyo]

I know somebody out there has some light to shed on this, unless the no reply is silently stating that there are no differences?

[linemen339]

Google the yj 4.0 to 4.2 head swap. I found many pages of that topic.

[BadAddetude]

Regarding cams, you might want to call and talk to these guys: http://www.cliffordperformance.net/index.html

Specialists in inline 6 performance. Sometimes it tough to get performance advice from the folks around here, because most are convinced the 4.0 is not a performance motor, more a torque generating truck engine. Done right, it can be anything.

[4.7stroker]

The cams are the same except for the fuel pump lobe so if you run an electric fuel pump it won't matter, the lifters are already hydraulic but new lifters should be installed when ever a new cam is installed, you use the 4.2 pushrods, make sure you check the preload. The waterpump will fit but watch rotation serp rotated backwards when compared to V-belt.
Here are your choices for Comp cams.
http://www.compcams.com/technical/Catalogs/106-07/16-19.pdf
I used the 68-201-4 and am very happy with it.

Dwayne

[dan_yoyo]

Thanks for the replies everyone. I will be checking out the links you posted.

Dan