will a head off of a 4.0 fit a 4.2 cj motor?????

jeepgdub

jeepgdub

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Aug 5, 2007
Location
charotte
Would it be possible to utilize a newer 4.0ho head and fuel injection mated to a somewhat factory spec rebuilt 4.2L block???. I have access to a low mileage head intake and fuel system with wires off a wrecked TJ. Will it work, and would it be beneficial? I have had no luck finding out if the head would match and how much work would be involved in wiring her to function. Any information will curb my curiosity for now. I like the idea of FI however there is a price to pay. I am hoping for positive answers on this one

Thanks in advanced for the info.
 
I know a friend of mine stroked a 4.0 using parts from a 4.2. I don't know exactly what he did but it riped. I also know he used mustang injectors. He also had to do some machining to the bell housing for the crank positioning sensor. Hope it helps.
 
people do it all the time, good upgrade contact uglyjeepoffroad on here, he has one of the best running 4.2's I have seen using some 4.0 parts
 
IIRC the stroker people use is a 4.0 engine, with rods, and crank from a 4.2
Not sure about the heads. I think they would work if the combustion chamber is the same or similar CC's. Might have too little or too much compression
 
you'll need a new exhaust manifold, the intake will bolt on. Try to get the 4.0L valve cover, because not all 258 heads are the same. I think a YJ 258 valve cover will work with 4.0L head, but the CJ heads/covers are different.
The key with a 4.0L head on the 258 is the coolant ports are slightly different. The 4.0L head will over hang some 258 blocks, and require epoxy or welding to seal the ports. I've read about people relying on a thicker head gasket to prevent this, but I wouldnt rely on that.
For the TJ efi to work on a carbed CJ, you will need a crank sensor to trigger the MPI. You can order a damper and sensor kit to make it work, I think the TJ uses something in the bellhsg.
 
jeepgdub said:
Would it be possible to utilize a newer 4.0ho head and fuel injection mated to a somewhat factory spec rebuilt 4.2L block???. I have access to a low mileage head intake and fuel system with wires off a wrecked TJ. Will it work, and would it be beneficial? I have had no luck finding out if the head would match and how much work would be involved in wiring her to function. Any information will curb my curiosity for now. I like the idea of FI however there is a price to pay. I am hoping for positive answers on this one
Thanks in advanced for the info.
Click to expand...

Lots of info here:
http://www.ifsja.org/forums/vb/

You'll have to search though.
 
thanks people, Ihave the info rolling. The EFI might be out of my range for now, but the 4.0 head is a weekend project. Thanks again,
 
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