Retro engineering

[JeeperJack]

Think before you speak. My. 85 CJ still has the stock 2.71 gears. I want to go to 31 tires. Low end torque is vital. Has anyone ever considered a 4.6 poor mans short block with a slightly reworked 4.2 head? I have a 4v intake and a several sizes of eddie carbs. Smaller ports and valves would enhance low speed velocity. Larger chamber would lower compression just a bit. Just really looking for 1500/ 3000 max torque. Any thoughts?

[Cheromaniac]

I'm not sure why you'd want to build a stroker and have it drinking through a straw (the 4.2 head). A ported 4.0 head will allow the engine to produce more torque across the whole rpm range. Mine produced at least 90% of maximum torque from 1500rpm to 4500rpm (peaked at 3500rpm). The smaller kidney shaped chamber of the 4.0 head has better combustion efficiency resulting in better gas mileage and lower emissions. I suggest you also use an '00+ intake manifold and make an adapter plate to mount the carb.

[JeeperJack]

Thanks. I concerned about the compression with a poor man's build. 9+ and spark knock is something I'm not wanting to deal with. A better price on the lower comp pistons would be great. What cam did you use?

[Cheromaniac]

I reused my stock '92 cam.
I suggest you go with the modified poor man's using the 4.0L rods and Russ' custom pistons. With a CR in the low 9's and a tight quench, you'll still be able to run 87 octane gas.
The '00+ intake manifold will also help as the curved runner design allows a more homogeneous distribution of the air/fuel mixture to all cylinders.
You might end up spending a bit more but you'll be much happier with the end result.

[Russ Pottenger]

This ^^^^^

[dirtdudeaz]

You mentioned your gears, almost expecting a question about them. A motor will help get you power, but are there plans to change your gears too? What trans do you have (T-176?)? I think you'll still fight your tall gearing for any low RPM torque you gain in a stoker. Just curious, what type of driving do you do...

[Cheromaniac]

I agree. With 31" tires and a 4.6 stroker, I'd suggest either 3.73 or 4.10 axle gears. They'll make a massive difference compared to the 2.71. Keep in mind that you'll need to change the speedo drive gear in the transmission tail housing to correct for the axle gear change.