4.2 or 4.0

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4.2 or 4.0 #846153 11/09/07 02:49 AM

Joined: Feb 2007

Posts: 29

MadGary

Getting the Wheeling Fever

I just got a 1980 CJ7 from my grandpa. The jeep was sitting in nothern california in the shrubs for 15 years. Its pretty amazing that there barely any surface rust on the whole thing. Its got a amc 360 with all the smog equipment taken off. Ive got the option to put in a 1982 258 4.2 carburated, or a 1993 Fuel Injected 4.0. Which engine is a better engine? Would the 258 be better than the 4.0 if it were fuel injected? What do you guys recomend?

Re: 4.2 or 4.0 [Re: MadGary] #846154 11/09/07 04:00 AM

Joined: Oct 2003

Posts: 7,768

Central Texas

BigJim

Web Wheeler

First thing to do is find out what gears are in the axles..
The engine you choose should be able to turn the wheels. If the gears are as high as I'm thinking you may be better off renewing the v-8..
But to answer your question. All things being equal the 4.0 is a far better engine. It is much harder to get everything installed for it than the 4.2 however.
If you are still in California you better check with the state before thinking of driving on their hiways with an altered Jeep.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist

Re: 4.2 or 4.0 [Re: BigJim] #846155 11/09/07 01:37 PM

Joined: Oct 1999

Posts: 2,211

Denver, Colorado

superdawg

Body Damage is Cool

If the engine runs well, find out from the state emissions tech center (NOT a testing center, although they could tell you who to call)what it needs to be legal before swapping motors.
In Colorado that rig could have a 50 state legal Howell TBI system installed on it and a new cat and you are good to go. Way easier than a motor swap and will run better.

As to axle gears those can be changed to match whatever size tires you want to run.

Nobody said building a jeep is cheap.

SD

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