Head questions

[Tin Medic]

What is the difference between the 4.0 & 4.0 High Output heads? If there is a thread on this already please point me in the right direction, cant find a thread using the search.

 

[mtnwhlr]

From what I have read the high output head flows better.

 

[Tin Medic]

Will I need anything else from the block or just head? I was told I should have it decked?

 

[Sasquach]

Will I need anything else from the block or just head? I was told I should have it decked?

Ideally you would have a machine shop go over it, mag for cracks, deck for flat, valve grind and seats as need.
Pulling a head off a junkyard engine and bolting it straight onto yours would be a shoot at best.
Take everything from the head up.

 

[IOPort51]

Tim Weavers 40 Head Article

this should get you started.

find the right head, take it to a machine shop, have the extra holes welded or filled with JB weld, do a 3 angle valve job and have it decked.

AMC l6 heads crack, it's what they do, usually at the valve. Sometimes they can be welded and re machined but not often. Find a donor at a PYP and pull the plugs, check for oil fouling, if they are clean and not brand new it's a good chance you found a winner.

 

[coldair]

Here is some info I found a while back about the diffrent years of heads and how they flow. Everything 4.0L, casting#, parts, differences - Great Lakes 4x4. The largest offroad forum in the Midwest

 

[Tin Medic]

Where is the head number stamped?

 

[IOPort51]

drivers side about 1/2 way back on the top, just outside the valve cover. take something to scrape the crud off with.

grab the push rods, valve cover with bolts, rockers, exhaust manifold if it isn't cracked. oil fill cap and valve cover vents for the PCV.

Where is the head number stamped?

 

[Tin Medic]

Due to the wierd placement of the gaskets I cant really see any numbers. Going to buy a head and set it up anyways and go from there.

 

[IOPort51]

you will find it, just pull the intake off.

 

[TheDirtyCJ]

AMC 258 i6 / 4.2l 4.0 Head Swap Results
check out this link in the forums my friend and I can help you with this. I still swear thats the best thing I've ever done.

 

[Tin Medic]

What link?

 

[Sasquach]

What is the difference between the 4.0 & 4.0 High Output heads? If there is a thread on this already please point me in the right direction, cant find a thread using the search.

Tech Specs

 

[coldair]

Thanks for the link for my link lol

 

[TheDirtyCJ]

What link?

Sorry didnt do that correctly, the link is called 'AMC 258 i6 / 4.2l 4.0 head swap results' its in the drive train forum.