another 258

[rr41mag]

I can get a AMC 258 i6 / 4.2l from a friend. What upgrades can be done or what would you do? It will sit on a stand for a while, just can't turn down the deal on it.

 

[PaRenegade]

I would like to be able to do that too. I'd bore it, new pistons, rings, bearings, cam, have crank checked, valve job; pretty much a total rebuild but I wouldn't get too carried away with performance stuff. It's still a AMC 258 i6 / 4.2l !

 

[IOPort51]

how many miles and what year?

I would mike the bearings and such and take a look at the cylinder walls but if at all possible, leave the bottom end alone, maybe a new oil pump.

All the fun stuff happens on the top end and the ignition. Head, header, MSD, TBI. on and on.

 

[CJim7]

4.0L head swap..no question. I would also swap out the ignition for a TFI or HEI.
Try to find some high compression pistons and a decent performance cam.

 

[Kane]

I agree to get rid of the dish pistons, go to some flat tops and bump the compression up on the bottom end, then get the 4.0 head along with a good ignition. Always set up the bottom end for success so it can handle mods down the road.

 

[johnnyreb]

not to highjack but what flat tops are you using? Do they need to be cut to clear the valves? I would like to ditch the dished pistons as well.

 

[Kane]

I dont have a AMC 258 i6 / 4.2l anymore but most flat tops have valve relief cut into them. Unless you are running a giant lift cam then they should clear fine. I have flat tops in my 350 with 0 decked block and Edelbrock Performer Aluminum heads. Valve clearance is no issue and i run 89 octane with around 10-1 compression.

 

[CJim7]

not to highjack but what flat tops are you using? Do they need to be cut to clear the valves? I would like to ditch the dished pistons as well.

This...to a 'T' :

I dont have a AMC 258 i6 / 4.2l anymore but most flat tops have valve relief cut into them. Unless you are running a giant lift cam then they should clear fine. I have flat tops in my 350 with 0 decked block and Edelbrock Performer Aluminum heads. Valve clearance is no issue and i run 89 octane with around 10-1 compression.