Jeep Strokers

I just found this board. I'm interested in turning my 4.2L in my 1979 CJ7 into a stroker for more torque and horsepower. Can someone point me to a place where I can get started gathering information? I'm mainly interested in torque/HP for various configs, sample parts list, etc. Just trying to assess the magnitude of such a project right now.
I have experience rebuilding engines, albeit older ones such as Model A, mini-truck, etc.
thanks for any help!

For these strokers, you would tear down your 4.2, save the crank, and use it in a newer 4.0 to make a 4.5-5.0, depending on budget. Build threads here or Dino's site in the faq section will have some base info for you

Looking at the Golen site, it looks like they make a stroker from the 4.2 block. Is that something that anyone here has done?

I'm not aware of any *stock jeep/amc* crankshafts with a longer stroke than the 4.2? A 4.0 head swap to the 4.2 block is also fairly common, but your bores will still be small.

I'm also not familiar with the off the shelf kits. They could be selling a custom crank

There used to be a stroker kit for the 4.2 but I don't know if it still exists. It's much more preferable to start with the larger 3.875" cylinder bore of a 4.0 block, and there's no shortage of those in junkyards since the engine enjoyed a 20-year production run.

Doing that very thing now.

4.2L block, cylinders bored 0.030 over bore (due to burned piston in #6);
* Edelbrock 4.0L aluminum head;
* New pistons stock compression;
* Comp Cams 4x4 Xtreme camshaft;
* Harland-Sharpe roller rockers;

* Clifford Engineering Dual Carburetor intake
* Dual Weber 38/38s
* Dual exhaust

I am informed that the 4.2L engine is already a striker of sorts, having been preceded by the 232.

Using that block and adding the 4.0 head basically accomplishes the same thing as the normal 4.0 stroker build, but with 4.2L cylinder bores.

You don't have to use the Edelbrock head of course, but a standard 4.0 head will need some adaptation to close off coolant passages that are not present on the 4.2L block.

It may be possible to use the 4.2L valve cover, but I chose not to do that. You must drill more holes to attach to the 4.0 head.

Cinaed57 wrote: ↑January 18th, 2026, 8:59 am I am informed that the 4.2L engine is already a stroker of sorts, having been preceded by the 232.

Indeed it is:

232ci (3.8L): Bore 3.750", Stroke 3.500"
258ci (4.2L): Bore 3.750", Stroke 3.895"
242ci (4.0L): Bore 3.875", Stroke 3.415"

However if you use the combination of a 4.0L block (bored +0.030") with the 4.2L crank you get:

Bore 3.905", Stroke 3.895", displacement 280ci or 4.6L

I see that it is technically possible to bore out a 4.2L cylinder to the 3.905 bore dimensions -- I wonder if anyone has ever done that.

It appears that it is strongly advised against. Cooling becomes a problem with thin bores at that point.

Cinaed57 wrote: ↑Yesterday, 8:09 am I see that it is technically possible to bore out a 4.2L cylinder to the 3.905 bore dimensions -- I wonder if anyone has ever done that.

Definitely not! That only applies to the 4.0L block.
The maximum safe overbore on a 4.2L block is +0.060", taking the cylinder bore to 3.81".