258 question

[Zorm]

for the 258 folks, I think I have a knock in the engine. The engine I have now if from a late 80's YJ. I know where I can get a 258 from an old 70s J-10. Are the older blocks better? or should I just rebuild the one I have.
Also, what would be a good cam, this will be street and some 4x4 driven.

thanks

[brielly]

Supposedly the older blocks are better. Something about more weights on the crankshaft possibly creating more torque. I'm sure someone more knowledgeable will chime in. The older blocks also have the 1/2 in. head bolts which makes the 4.0 head swap easier too.

[Cecil14]

The YJ block with also have 1/2" head bolts. The 7/16" bolts only lasted from like '80-86 or so.

The older engine will have 12 weights on the crank, producing a bit more torque (less revving though) and a much smoother idle.

For economy and drivability a 4.0L head swap is definitely the way to go. As for a cam, I ran a Comp Cams 68-231-4 and loved it. It made a TON of power in my stroker, but I suspect it would have similar results in a mostly stock 258. Honestly the biggest performance mod you can do to a 258 is the 4.0L head (short of boosting it).


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