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Robbins 02-26-2013 11:31 AM

engine help!!
Alright guys here is what ive got going on in my head. Ive got an 84 Cj7 with the 4.2 liter straight six. Im wanting to rebuild the motor, bore it out, upgrade carburator and throw in a cam. Not sure what to bore it out to or what kind cam or carburator to get. I still want to be able to drive it on the road fine but tair up the trails. Ive got 3.5 inches of lift and it sittin on 35'' cooper stts. Any suggestions? Not too experienced on motors so need any and all kinds of advice. Thanks!

lynn 02-26-2013 02:31 PM

I'll suggest swapping in a mid-90s 4.0L from a ZJ or XJ... plenty of power, fuel injected.
Or combine the two engines and do a stroker.
Lots of info out on the web on both of these.

If you insist on going with a rebuild/cam/carb, I can't recommend a particular cam but I can say that using a Motorcraft 2100 carb is a good way to go. Economical, and not very sensitive to off-camber running as some other carbs are.
Again, lots out there on the 2100 if you search.


Robbins 02-26-2013 02:40 PM

Any idea on how much swappin motors or building stroker would run?

von-klink 02-26-2013 06:22 PM

Depending on your trusted local machine shop.The six starts at $1500
for full rebuild. You can build a fairly nice chevy motor for what it costs
for the AMC 258. The V8 gets run up in cost, by the converstion parts.

Power costs money! how much power do you want?


Robbins 02-26-2013 09:18 PM

In all honesty I'm not sure. I want to still be able to drive it on the road but I wanted to do great off road to. 1 of my buddies was telling me to just just bore out to 30 and throw in a new camshaft and carburetor. He said that would be plenty for off road and still drive great on the road. So I guess this point I'm really open to any suggestions just trying to figure out the best for my money and what I want.

Jeep78 02-26-2013 10:06 PM

Hey Robbins. I have a 82' cj7 with a 4" suspension lift and 2" body lift. I'm also sitting on 35" tires and want to remove the body lift. Was wondering how your clearance is with the 3.5" lift? It looks like nothing would rub but I'm worried that when I'm off road and hit a big bump ill take a chunk out of my tires. Just wondering what you thought and what you've experienced.
Can't help much with the motor question but can tell you I have a Chevy 305 that has been rebuilt and I'm happy with it. It's been converted to a fuel injection as well. At the end of the day it's how much you want to spend. As stated above: power cost money.

lynn 02-27-2013 06:39 AM

Your buddy is right: you can bore it, cam & carb (install a Motorcraft 2100 on the 258) will give you plenty of power for on-road and offroad.
Upgrade the stock ignition system to GM HEI or Ford TFI (Team Rush upgrade).

Check out your axle gearing. If running 35" tires your diffs should be running 4.56 for a good compromise of on-road-off-road power. The stock gears will make the rig feel sluggish offroad and you won't be able to go slow enough over some obstacles.

Robbins 03-01-2013 12:50 PM

Ty so much guys. Im gunna have it bor ed out after the jeep meet in OK next weekend. Jeep 78 im not sure just upgraded to 35s. Drunk ves awesome on road but ill let uk after next weekend how it is on the traila.

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