258 head?

biscuit wrote: 4.0 head does look like the way to go thankyou.

billd wrote: biscuit wrote: 4.0 head does look like the way to go thankyou.   I owuld not mind doing that on my sx eventually, but for now, I just want to get it up the end of the driveway! I'll start collecting the parts to make the swap, however............   OK, can one tell the differences between HO and ordinary on a 4.0 head by looking? What years or vehicles used them? Would a non-HO head be better than stock 258 head? I can always drive a head to Nevada, IA to get a head ready to bolt on (assuming I find one).

Purple is correct -- 87-90 = "standard" 4.0L, 91+ = HO. If the intake and/or exhaust manifold(s) is one you can easily tell the difference -- the standard 4.0L has an EGR valve and tube on the "header", the HO does not.

There's not that much difference between the standard and HO heads. The intake ports on the standard are about 3/8" higher than 232/258 intake ports to get a smoother flow into the head. The HO has the intake ports raised another 1/8" for the same reason -- a bit better flow.

There is a 13 hp difference between the standard and HO engines, but it's not all in the head. The camshaft is advanced 2-3 degrees and the EFI program is tweaked. This makes a bit more power, but also moves the power output a little higher in rpm. The difference in power isn't as great if you run the HO engine at the same rpm as the standard.

The head should add no more than half the gain -- maybe 5-7 hp, but that's just a guess on my part. It's not worth passing up a good deal on a 87-90 4.0L head for a later one, but if you're paying about the same price you may as well get a few extra ponies. It's definitely worth changing a 258 head for ANY 4.0L head though.