de-stroking the 258

[akadeutsch]

I am considering a CJ7 build. Id like to use the original 258 but I’ve got to add a twist. I am wondering, if stroking an engine adds torque as we see it do, then does de-stroking an engine mean potential horsepower gains? By way of spinning what will be a smaller mass around a tighter orbit and reducing its rotating mass as much as possible (lighter weight hyper pistons and as few counter weights as possible)?
I'd like to see if I could build a horse power engine by de-stroking the 258 with a 242 crank. Did they ever produce a light weight low number of counter weights 242 crank? Ide use the 258 rods. I could punch it .060 over. Balance the rotating assembly to the .0000, advance the juice out of it and see how fast she might spin.

[SkylinesSuck]

I think you need to consider what the limit to horsepower is currently. I believe it's head flow (or lack of) and maybe engine harmonics. I think you would waste time and make less power. Maybe somebody will disagree.

[akadeutsch]

Valid point. I was reading an article about a Chevy straight 6 and thought....we could do that.
http://www.enginelabs.com/news/dyno-vid ... orsepower/
The article brings up similar concerns to yours with the Chevy engine. But they pulled 320 hp so I might still build it. I've had the doors open to my own shop now for a little bit and ive already collected nearly enough parts to put this together. By the time that I can afford the cj7 I'll have all the parts. I think all I'm missing now is a head at this point. It'll take doing the math to see if it's worth it. Or if it'll even compress. My estimate is that it will end up around a 3.8. Custom piston pin height? And who knows how fast it'll spin? I've heard that there is a harmonic imballance around 5grand. I wonder how it'll spin at 6+. I don't think I've ever spun my 4.6 over 5k.
I see this as a fun challenge with only Mall Crawling intentions. I'm.just curious to see what a straight 6 sounds like spinning that fast. Heehaw

[IH 392]

The Chivy has a bigger bore letting it use bigger valve and less shrouding, getting the air in, the AMC engines have smaller bores and valves.