258 4.0 Head Swap Results

[coldair]

When i do start working on this jeep i will start a build thread LOTS of pictures too

 

[TheDirtyCJ]

I put about 20,000 miles on mine before the motor regrettably blew a piston skirt (I had a spare 401 lying around, no rebuild on the 6)

I never ran into ANY issues running this engine. I was pushing 11-11:5 compression with the flattys and never once encountered the dreaded pinging associated with high compression and regular gas.

Likewise, the previous misinformation can just be thrown out the window. The valvetrain between the 4.0 and AMC 258 i6 / 4.2l is identical except for the valves themselves and there may be a slight variance with the pushrods, but I've ran into that between different years of AMC 258 i6 / 4.2l ...so that's not an issue. The rockers and pivots are all the same. Springs...no issue.

I used a TFI ignition, so I didnt get the test the "theory" of worn dizzy gears.

Pound for pound, and dollar for doller I think this is the best modification that can ever be done to the AMC 258 i6 / 4.2l . It makes it a whole different engine

NO PROBLEMS to report I still swear by it being the best thing I ever did!

 

[cjattic]

I am planning to begin this swap soon. I figure it should cost about $2500 with doing some maintenance. The block I was planning to put the 4.0 head was a 1973. While doing research I noticed the push rods in the 1973 AMC 258 i6 / 4.2l are solid where newer AMC 258 i6 / 4.2l engines have hollow push rods. I believe this might cause an oiling problem because the 4.0L uses hollow push rods to oil the head. I would assume the 4.0 head gets oiled from the push rods. If this is true I would need to use a newer block to swap the 4.0 head onto. I noticed the AMC 258 i6 / 4.2l has hollow push rods beginning in 1974. I have not looked at push rods yes though, according to parts at rock auto the push rods are solid not hollow as the 4.0 push rods are.

Is my concern justified?

I think I am going to play it safe and buy a early 1980's block. I know those blocks have hollow push rods.

 

[73CJ]

My 73 rods were hollow. Where did you hear that? How would the oil get up there then?

 

[Rescue Diver]

The older inline 6 cylinders did have solid push rods and a rocker oiler under the valve cover from what I've read. I'm pretty sure that they still had hydraulic lifters though, so I'd guess that you could switch to hollow push rods and it'd work fine with a late model 4.0 head, but do the research to make sure before throwing it all together!

 

[Rescue Diver]

My 73 rods were hollow. Where did you hear that? How would the oil get up there then?

He might have a AMC 232 i6 instead of a AMC 258 i6 / 4.2l ? It's been a long time since I read about what works with what for a 4.0 swap, so I'm only 100% certain about the swap I did.

By the way, back to the original subject, I've put a whole lot more miles(around 20k or so) on my AMC 258 i6 / 4.2l with the 4.0 head and it's still purring like a kitten with a nice quiet valve train.

 

[alaskaviper]

I'm collecting parts now to do this swap. Got my exhaust manifold. Still trying to track down a head, considering the clearwater head with the welded water holes. Seems like it may be cheaper after the $200 junkyard head then getting the head rebuilt. Valve cover will be the easy part to get. I'm trying to figure out if I want the original cover or get the aluminum blue cover to match the engine.

I wanted to add this bit of infor for the spacers for the different size bolt holes, I didn't see this in here so here it is. Heres a link for 1/2" spacers for the 7/16" block holes. Summit racing has them. Part #TFS-51400419
Trick Flow Specialties TFS-51400419 - Trick Flow® Head Bolt Bushings - Overview - SummitRacing.com

 

[Rescue Diver]

I'm collecting parts now to do this swap. Got my exhaust manifold. Still trying to track down a head, considering the clearwater head with the welded water holes. Seems like it may be cheaper after the $200 junkyard head then getting the head rebuilt. Valve cover will be the easy part to get. I'm trying to figure out if I want the original cover or get the aluminum blue cover to match the engine.

I wanted to add this bit of infor for the spacers for the different size bolt holes, I didn't see this in here so here it is. Heres a link for 1/2" spacers for the 7/16" block holes. Summit racing has them. Part #TFS-51400419
Trick Flow Specialties TFS-51400419 - Trick Flow® Head Bolt Bushings - Overview - SummitRacing.com

I take it you don't have a pick n pull type junk yard near by? I nabbed my new head, valve cover, and even the push rods and head bolts really cheap by pulling it myself from a 1995 Cherokee.

Thanks for posting the link for the spacers. Fortunately I didn't need them since my block is a 1979 that takes 1/2" head bolts.

If you don't go with the welded water jackets, you'll be fine with the JB Weld method as long as you clean the jackets good before applying the JB. Mine hasn't leaked a drop ofter all of these miles.

 

[alaskaviper]

I take it you don't have a pick n pull type junk yard near by? I nabbed my new head, valve cover, and even the push rods and head bolts really cheap by pulling it myself from a 1995 Cherokee.

We do have one but they want $200 for head and $50 for cover. After I get the head rebuilt, I might as well order the clearwater one and be cheaper with welded ports.

Thanks for posting the link for the spacers. Fortunately I didn't need them since my block is a 1979 that takes 1/2" head bolts.

It took me a bit of searching to find these so I figured anybody planning to do the swap looking at this thread will now have more info in one spot.

 

[Rescue Diver]

We do have one but they want $200 for head and $50 for cover. After I get the head rebuilt, I might as well order the clearwater one and be cheaper with welded ports.



It took me a bit of searching to find these so I figured anybody planning to do the swap looking at this thread will now have more info in one spot.

They want $250 for a head and valve cover even though you would be pulling the parts yourself??? WOW!!! I only paid $70 for both of them plus the 4.0 push rods and head bolts. I think I'd be looking for another source too! Maybe you can find someone parting a 1992-1999 Cherokee on Craigslist? Keep in mind that 1996-1999 castings flow just as good as the 1992-1995 but they don't have the temp sender hole behind the valve cover drilled.

Don't forget that the rockers aren't adjustable, so you'll need pushrods of the correct length. I found the stock 4.0 pushrods to be the correct length to give the perfect amount of lifter preload. My stock 1979 AMC 258 i6 / 4.2l pushrods were just a tiny bit too short.

 

[alaskaviper]

Yeah I would have to pull the head myself. I deen looking on craigslist but timing never works out. I seen a bundh of 4.0L engine for cheap. Now that I decided to do the swap I can't find any. And I'm in Hawaii so its a Limited search area..

How did you go about measuring for the correct pushrods? I'm not to sure on that or if theres anything special for putting the rocker arms on.

 

[Rescue Diver]

Yeah I would have to pull the head myself. I deen looking on craigslist but timing never works out. I seen a bundh of 4.0L engine for cheap. Now that I decided to do the swap I can't find any. And I'm in Hawaii so its a Limited search area..

How did you go about measuring for the correct pushrods? I'm not to sure on that or if theres anything special for putting the rocker arms on.

I don't remember the exact amount of preload that the lifters call for, but with adjustable rockers, it's between 1/2 and 1 rotation of the nut, so it's not much. Hydraulic lifters are pretty forgiving and will allow and compansate for different amounts of preload, as long as it's not too much. If the push rods are too shorts, you'll have a lot of clatter.

The rockers just bolt directly to the head. They can be shimmed higher with spacers to compensate for a slightly too long push rod, but if the push rod is too short, there's no way to adjust the rocker down to make up for it.

 

[alaskaviper]

So I finnally got most of my parts together to get started on the swap. I do have one question though. We I was getting the head, the guy said it was #7120 but when I got it, it was # 0630. I alrady got a valve cover from a 92 XJ and was wondering if anybody knows if that valve cover will fit on the 0630 head? When you look up gaskets, thay stop at 95 and have a different one listed for newer years. So either I go and buy another valve cover from a new XJ from the junkyard (I'm sure they won't take the old one back in exchange) or use the 92. Any suggestions?

 

[Rescue Diver]

So I finnally got most of my parts together to get started on the swap. I do have one question though. We I was getting the head, the guy said it was #7120 but when I got it, it was # 0630. I alrady got a valve cover from a 92 XJ and was wondering if anybody knows if that valve cover will fit on the 0630 head? When you look up gaskets, thay stop at 95 and have a different one listed for newer years. So either I go and buy another valve cover from a new XJ from the junkyard (I'm sure they won't take the old one back in exchange) or use the 92. Any suggestions?

Your 0630 head is pretty much the same as a 7120 except it probably doesn't have the sender hole drilled behind the valve cover, and the exaust ports look a little different, but they flow just about as good, and should take the same gaskets as far as I know.

 

[alaskaviper]

I would too, no question, but when we do multiple changes it is not possible to attribute the performance to any one thing.

I don't have fancy test equipment but I do have a hill. It's about 1/8 mile 20 degrees and paved. I start at the bottom in 2nd gear and time the distance with a stop watch. As long as I am doing one thing at a time I can get a pretty good idea how much bang I got for my buck. We need to establish a personal constant to measure against.

I am not saying the head swap is a bad idea, it is a good one. I had a cracked AMC 258 i6 / 4.2l head and this was the very best solution. I am saying there is a lot of mist and smoke blowing around this and a lot of other modifications because we can not document the results in measurable quantity.

I was upset it was the 0630 because I wanted to use the same temp sender but after careful inspection my 0630 head DOES have the hole for the temp sender. Good news. I went ahead and got a valve cover from junk yard for the same head just so it's correct.

Now I'm trying to figure out the EGR stuff between intake and exhaust. Or get the Clifford intake and exhaust? I have howell tbi so not sure what will be best. Oh decisions. What sucks being military is I don't know what state I'll move to and emission standard change between states.

 

[Sasquach]

Don't forget you have to run the 4.0 exhaust now, but that's a good thing.

 

[IOPort51]

https://picasaweb.google.com/85YellowCJ7/40HeadSwap#

YELLOW85CJ7 did a very cool thing and mounted his EGR to a 4.0 exhaust manifold. Here are his pictures and below is the thread he talked about it in.


http://www.jeep-cj.com/forums/f2/4-2-intake-4-0-head-14083/

I am sure he would tell you all about the adventure if you sent him a PM.

If I ever find it convenient to pull the manifolds, this is going to happen to mine.


One more thing, one of the guys actually did a dyno on a head swap and got about 35 HP gain.

 

[73CJ]

He might have a AMC 232 i6 instead of a AMC 258 i6 / 4.2l ?

No it's a AMC 258 i6 / 4.2l . Hollow push rods. Being 2nd owner for 36 years, motor was never cracked before I did. So they absolutely hollow.

 

[alaskaviper]

Well I finished my head swap finally. So here's what I went with: 0630 head, AMC 258 i6 / 4.2l pushrods, JBA Header, new cat and flowmaster 40 series muffler - 2.5" pipe. with a howell TBI (was installed before the swap).

Heres a link to a small video with how it sounds.
258 w/ 4.0 head - YouTube

Thanks for all the help guys.

 

[coldair]

Well I finished my head swap finally. So here's what I went with: 0630 head, AMC 258 i6 / 4.2l pushrods, JBA Header, new cat and flowmaster 40 series muffler - 2.5" pipe. with a howell TBI (was installed before the swap).

Heres a link to a small video with how it sounds.
258 w/ 4.0 head - YouTube

Thanks for all the help guys.

Did you you call Howells up to see if you need a new program burned? Would be interesting to see if it needs one or not. On my motor I will be running a 4.0 head and different cam I call Howells they told me I will have to get a chip burned. I don't know if the cam and head combo is why or it might be the cam that made it need the chip.