258 bottom end with 4.OL head

[Eagle-Mark]

I've got a 258 that has been well cared for with 66k miles on it. Plan is to leave it alone and install a 4.0L head that I have from a 91 with a casting of 7120 I think.

I've done a lot of online research and thought I would through it out there for a review from people who have done this.

My big qestion seems to be correct numbers for decking head and some articles say to deck the block (which I probably not as it's not coming out or apart) so how much to cut head? Use a performance head gasket, any advice?

Also cam choice? Looks like a set of Clifford headers. Not sure if I am going to use a clifford intake or one off a 199 up seems to be of tunde port design?

Any porting or matching needed with this setup?

Fueling will be done by a Gm TBI system because I do them all the time and tune/burn the chips. Although I could do a MPFI with the Jeep injectors but would need the injector information. There's lots of tunable options out there.

 

[Dr. Dyno]

You don't need to deck the block at all and you'll only need to deck the head the minimum amount required to make the surface perfectly flat. Depending on the year of your 258 block, you might need to block off some of the triangular water ports in the head with steel epoxy.

 

[Eagle-Mark]

Depending on the year of your 258 block, you might need to block off some of the triangular water ports in the head with steel epoxy.

See that one I never read... the block is a 1973 in it's original vehicle

 

[Team Willys]

Ok... question... while you can put a 258 intake onto a 4.0 head ( I have done done it before), you do have to modify it quite a bit. Not to mention, you HAVE to run a 4.0 exhaust header and or manifold, and those interfere with the 258 intake. So that's another issue. Also, why use a 99+ intake if you are planning on adding a TBI setup to this? Doesn't make much sense to me. You would have to machine the heck out of the intake, plus make an adapter for the TB, plus find a way to fill in the injector bungs, just to use any 4.0 intake and run TBI.

I just don't understand why I guess... It seems you are going through a butt load of trouble to put on a system that in the end will produce less power than a MPI setup. Even if you don't have the tuning capablities that you have with the GM stuff, I would still run the Jeep engine management. You will get more power and it is also pretty much a bolt on swap by going this route.

Thats my .02.

 

[Dr. Dyno]

Here's a helpful article 4U:

http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=277013

 

[Eagle-Mark]

Ok... question... while you can put a 258 intake onto a 4.0 head ( I have done done it before), you do have to modify it quite a bit. Not to mention, you HAVE to run a 4.0 exhaust header and or manifold, and those interfere with the 258 intake. So that's another issue. Also, why use a 99+ intake if you are planning on adding a TBI setup to this? Doesn't make much sense to me. You would have to machine the heck out of the intake, plus make an adapter for the TB, plus find a way to fill in the injector bungs, just to use any 4.0 intake and run TBI.

I just don't understand why I guess... It seems you are going through a butt load of trouble to put on a system that in the end will produce less power than a MPI setup. Even if you don't have the tuning capablities that you have with the GM stuff, I would still run the Jeep engine management. You will get more power and it is also pretty much a bolt on swap by going this route.

Thats my .02.

Up in the air on TBI on probably a Clifford intake, but what I am looking at now is if I can use the Jeep MPFI injectors or ones capable of running with GM ECMs because they are so easy to tune...

 

[sandaddik2]

I know dustin webster runs a 4.0 block with a 4.2 head and said it was pushing 350 hp with about 380 ft/lbs of torque while testing for koh 09

something to consider if you want power