beautiful day for a head swap

[johnnyreb]

Last two days have been sunny and mid fifties here in TN. So I decided friday to pull the stock AMC 258 i6 / 4.2l head and finally drop the rebuilt 4.0 head that been waiting months. The removal was pretty easy and straight forward, although heavy and awkward working alone. Lucky me, my AMC 258 i6 / 4.2l came with 1/2" head bolts factory so no shims required. Used 1/2" all thread for alignment pins. Started to install head bolts only to realize that 4.0 bolts are shorter on the side under the valve cover, little tip for others to watch when swapping heads. Now to finish bolting on the other items. Looking forward to seeing the power difference.
Anybody know if the AMC 258 i6 / 4.2l push rods will work or do I need the 4.0 push rods?

 

[Sasquach]

I reused my AMC 258 i6 / 4.2l rods. Had the same bolt issues so if you had read my headswap thread you would have been ahead of the game. LoL

 

[johnnyreb]

I probably read your thread at some point and time, but i've slept sincde then..lol Oh well it's on, just got to button it up.

 

[Bent]

I would use 4.0 pushrods. If you're using a rebuilt head, I would invest in a set of rocker arm bridge shims. http://www.summitracing.com/parts/crn-99179-1?seid=srese1&gclid=CJStzIjvnMMCFVJhfgod6RkAoQ.
When the valve seats are ground, the valve will set deeper into the head causing the pushrod to preload the lifter too much. The shims under the bridges will cure the tappity tap you get sometimes with a rebuilt head and no lash adjustment.

 

[hole]

Don't think it matters, the research I came up with spec'd the pushrods as exactly the same. I used my AMC 258 i6 / 4.2l pushrods and they are working great.

 

[Dan86CJ7]

is there a full thread on this swap? i keep reading about it and think i may have a crack..so maybe replacement would be better with a 4.0 head?

 

[johnnyreb]

use the search function here and on google. You will find plenty of hits. Some 4.0 heads are better than others.

 

[johnnyreb]

Happy dance time. Found the egr tube and bell crank for my aluminum divorced intake at the local pick n pull on an 81 spirit for 15.00. If i had the time and money it also had the serpentine setup with low mount alt and a/c pump.

 

[johnnyreb]

More happy dance. It's running again, although a little throaty with only the header. Can't wait to get it back out and see how the power feels.

 

[Sasquach]

Im sitting on the edge of the couch waiting to hear

 

[ThisGuyUKnow]

Anybody know if the AMC 258 i6 / 4.2l push rods will work or do I need the 4.0 push rods?

The push rods and the rockers are the same PN according to the parts catalogues so I'd say either or.