building a 4.2l

[1986cj7]

Another question. Will fi bolt onto the AMC 258 i6 / 4.2l manifold? The reason I ask is I plan on polishing and porting the intake, but if fi will not bolt to it I will not waste my time on the old manifold and just get a 4.0l intake and port and polish it. Thanks

 

[deadfeat]

You will need the 4.0 head for FI. Almost 100% sure.

Sent from my Galaxy S3 with Taptalk 2

 

[IOPort51]

Chevy TBI will fit the AMC 258 i6 / 4.2l manifold as will the Howell. You can even use the AMC 258 i6 / 4.2l head, the 4.0 head breaths better so it is the best choice. The results of port and polish are negligible from all reports but whatever floats your boat.

just be sure the ports actually line up on the head to the intake manifold. It is very easy to misaligne them on assembly.

 

[1986cj7]

Chevy TBI will fit the AMC 258 i6 / 4.2l manifold as will the Howell. You can even use the AMC 258 i6 / 4.2l head, the 4.0 head breaths better so it is the best choice. The results of port and polish are negligible from all reports but whatever floats your boat.

just be sure the ports actually line up on the head to the intake manifold. It is very easy to misaligne them on assembly.

Thanks, also thanks for the tip on reassembly. I planned on doing the porting n polishing myself. A very little at a time as not to screw it up. Not sure how much it will gain like you said. I guess back to reading more on the net.

 

[1986cj7]

After some more reading I guess I will only be porting the heads and manifolds to the gasket. It looks like the rest would be a waste of time. Maybe smooth the edges on the combustion camber. Thanks IOPort51 for your incite.

 

[1986cj7]

Well I'm looking into a Clifford header the ad on Clifford performance says that this header will inprove 18-22%. But does say what. This is the header.Clifford Performance: 57-2015 HEADERS Jeep 1987-2005 w/ 242 (4.0L). I was wondering what ya all thought or knew of this. Just don't know if I want to fork out 359 plus shipping. I'll have to buy a header to fit my new head but can get a stock for half that. Some say not to waste money on a header for a AMC 258 i6 / 4.2l .