Need some edamacation

[brentagade]

I have a 78 CJ5 with the stock 258 and T150 tranny. So with a 4.0, you use a 4.2 crank.....what about flip/flopping....If I keep my 4.2 block, would I use the same crank or up it to another? Or am I completely out of whack.

Also, I've heard about putting a 4.0 head on a 4.2 block? Does this really do that much vs machining or upgrading to a new 4.2 head?

How does everyone feel about aftermarket fuel injection over a carb? Is the Howell fuel injection any good or would a stock unit from a late model work.....



Thanks
Brent

[Flash]

they say, that a 4.0 on 4.2 is a good improvement, but there is a lot of work to make the 4.0 fit the 4.2.
then you can't bore the 4.2 out to a 4.0 bore diameter, AKA valve shrouding .

Personal i thing you would be better off with a 4.0 block and add you crank and maybe rods to that.
I understand you thinking that it would be simpler to just keep you long stroke block and add to it........but its just not that simple.

If you are deturmind to go this route, read up on some post in the "Swapology" section on this site. it will help understand how it's done.


Flash

[5-90]

The later head on the earlier block will usually net you some performance improvement - the head does breathe a bit better, and the fuel injection also helps.

If your block uses 7/16" head screws, you'll need to have sleeves made to go around the screw shanks to locate the head (242ci heads use 1/2" screws.) If your block uses 1/2" screws, you're golden.

Using the 242ci crank in the 258ci block will net you a fairly significant /decrease/ in displacement and torque - since you're "destroking" the engine. You'll make it undersquare, which is usually done to make a high-revving engine or to accommodate forced induction.

[brentagade]

So then maybe keep the bottom end and just bore it out some, then maybe a 4.0 head and FI??

Got a lot to learn...

Thanks!