dumb question about using a 4.2L crank/connecting rods for stroker rebuld

hey i have question about using a 4.2L crankshaft and connecting rods for a stroker rebuild.

I am looking for a crankshaft and connecting rods from a 4.2L and someone said they have one from a 4.2L short block

this might be a dumb question but all the 4.2L are shortblocks arnt they? and it should be fine?

"Short block" and "long block" are states of assembly.

A "short block" is an assembled engine block, less cylinder head and bolt-ons (no water pump, distributor, sheetmetal, and the like.) Essentially, it's the block casting and reciprocating assembly (crankshaft, rods, pistons, &c.)

A "long block" is a "short block" with the cylinder head(s) assembly(ies) attached. Still no sheetmetal or bolt-ons, but you'd have the major castings, reciprocating assembly, and valvetrain.

The next stage is considered a "crate" engine - long block plus bolt-ons and sheetmetal (oil sump, valve covers, and that.) No manifolds.

"Short block" and "long block" are irrespective of displacement or maker. Those relative terms become "big block" and "small block," and are usually applied to V8 engines.

You can also have "wide deck" and "narrow deck" (the AMC six broke across the 1974-1975 model year for this, as I recall,) and "short deck" and "tall deck" engines (I think AMC broke this in the six and V8 engines,) but that's another story entirely.

Your 258ci crankshaft will have a stroke of 3.895" - which is what you want - and you just have to worry about the crank snout. If it's the earlier V-belt snout, it will be 1cm longer than the serpentine belt snout on the 6-242, so you'll either need to have it trimmed when you have the crank cleaned up (a simple operation,) or you end up cutting a spacer ring off of the old harmonic damper (which, as I recall, goes between the screw head/washer and the serpentine damper.)

awesome thanks for the information.

Keep in mind you'll need new pistons

cant u use 4.0 pistons if u use 4.2L connecting rods and crankshaft.

I thought a u only needed new pistons if u used the 4.0L connecting rods

You can use 4.0 pistons with the 258 crank and rods. But, does your block need boring?

There are other considerations you need to investigate. Search "poor man's stroker", an excellent website should come up of Dr Dyno's.

between Dr.Dyno's posts here, his website, and www.jeepstrokers.com you can find all the information you will ever need. it's all been done before, every combination you can think of, and the guys over at jeepstrokers really know everything about em. Their forum is packed full of information, and quite a bit of it is directed at newbies to building their first stroker.