350 or stroker or 4.2 - Page 2 - JeepForum.com

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post #16 of 20 Old 02-05-2013, 10:12 AM
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1989 YJ Wrangler 
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I did the "poor man's" 4.5 stroker, and it cost more than a grand.

If you only have a grand to work with, I'd rebuild the 4.2 and do a TBI conversion.

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post #17 of 20 Old 02-05-2013, 10:14 AM
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Originally Posted by Drix View Post

If your gonna do the head wouldn't you be able to move the manifold and bring the efi from a 4.0 over also.

build thread: http://www.jeepforum.com/forum/f22/skyj-eccentric-build-1467426/ '90 YJ 5.2 magnum MPI, AX15, NP231 SYE, Dana 30 4.56 open/ 8.8 4.56 detriot locker. 1" shackles
2" BL, 4" stretch all on saggy waggy springs.
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post #18 of 20 Old 02-05-2013, 11:11 AM
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But that involves a bit of wiring, new computer, fuel pump, etc.

That might be a little much for shop class.

probably out breaking stuff.
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post #19 of 20 Old 02-05-2013, 02:37 PM
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1989 YJ Wrangler 
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Originally Posted by skyj View Post
Yep I run a 4.0 head on my 4.2. You will definaltely notice the power difference. There are some modification to the head and also the intake you have to do to make it work. Here is a link to my build. I have a link in my thread to a very good write-up on a 4.0 head swap its what I used to do mine. Been running it for 3years now http://www.jeepforum.com/forum/f12/s...build-1467426/

Originally Posted by MLJeeper View Post
If you do the head swap, have your machinist shave the head enough to give you a .5 to 1 point bump on compression. Give you a decent boost in torque for little investment.
Thx for the link, good info here!

Originally Posted by Beachcruiser View Post
For a Grand (with access to a shop) I would:

Do a leakdown test to see if your 4.2 has good ring seal.

If so, I'd install the following:

4.0 Head & exhaust header.
New performance intake manifold (offy, etc) and small 4 barrel carb.
Upgrade ignition/coil system.
If ring seals aren't good, still worth doing or no? Good to know you can still run a carb with 4.0 head. Anyway to make this setup smog legal in CA??
OP I don't mean to ask all these questions in your thread, hope you don't mind since they're somewhat relevant.

Originally Posted by Drix View Post
If your gonna do the head wouldn't you be able to move the manifold and bring the efi from a 4.0 over also.
Possibly the method above keeps the cost and labor to a minimum. Considering you would need new ECU, wiring, sensors, injectors, fuel rail, etc, etc for efi...

89 YJ 4.2L http://www.jeepforum.com/forum/f12/kgb-89-yj-storyline-build-thread-1520814/
96 XJ 4.0L http://www.jeepforum.com/forum/f177/600-96-xj-budget-daily-overland-build-1855418/
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post #20 of 20 Old 02-05-2013, 02:43 PM
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1992 YJ Wrangler 
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I like straight six's. (in Jeeps)
Clifford Performance specializes in performance parts for straight six engines. They are pricey though.
The Company name is 6=8

Why not build the internals, then as your budget allows add headers, cast aluminum intake, carb ect?

Headers from Summit

There is a stroker kit for the 258, but it is a budget buster.

If you look in my sig, I still kind of miss my CJ7. Never should have sold it. It had a very solid motor with cam, headers, intake and carb, and had work done to the head to make it flow better. It was a while ago but I think it had valves from something else. It had gobs of power and happily revved to 5000 rpms.

I think you can use the better flowing head from the 4.0.

Look for part that are emission approved.

Do lots of research and make a plan and a list. Build it right the first time and it will serve you for a few hundred thousand miles.

What happens in my Jeep, stays in my Jeep
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