258 4.0 Head Swap Results

[Rescue Diver]

this might be a really dumb question but will this head swap work on a AMC 232 i6 engine also?

I wouldn't call that a dumb question. If what I read is correct, the AMC 232 i6 is just a shorter stroke AMC 258 i6 / 4.2l , so I would think it would work. But there are some things you'll have to take care of. Also, if what I read is correct, the AMC 232 i6 used solid push rods and some kind of oil sprayers under the valve cover rather than oil pumping through the push rods to lube the rockers. If that's true, you'd have to figure out what's required to either relocate the existing valve train oiling system to the new head, or switch it all to the newer style AMC 258 i6 / 4.2l lifters, hollow push rods, and rockers.

I have no experience working on a AMC 232 i6 . I only know what I've read on the net, and I don't always trust everything I read for reasons that are abundantly clear in other threads.

Maybe someone else can verify this for us?

You'll also want to find out what diameter the head bolts are. 4.0 heads take 1/2". AMC used 1/2" on the AMC 258 i6 / 4.2l through 1979, but switched to 7/16" in 1980, so those will require spacers to align the head, and lighter torque. I seem to remeber reading something about Chrysler going back to 1/2" on the last couple years of the AMC 258 i6 / 4.2l in the early Wranglers, but I could be wrong on that. I have no idea what head bolts a AMC 232 i6 takes.

 

[IOPort51]

I didn't know that about the push rods, that could complicate things a bit.

I would suggest you do the ignition upgrade, HID or TFI and a two BBL carb, maybe an MC2100, before re-engineering the oiling system. But if /when you figure out how to do it we definatly want to hear about it.

 

[Rescue Diver]

I didn't know that about the push rods, that could complicate things a bit.

Yeppers. I'd read about the drastic changes that took place in the very early 70's with the valve train oiling system, but I've never worked on one that old.

This subject came up in another thread where someone who shall remain nameless mistakenly reported that the oiling systems of the 4.0 and the AMC 258 i6 / 4.2l heads were totally different, even though they are not. That's the danger of regurgitating info one reads on the net as fact when you really don't know. That's why I said I read it but would like someone to verify it. I'd like to at least know exactly what year AMC changed from solid to hollow push rods.

 

[IOPort51]

I am looking at my 1977 FSM and there is no mention of a difference in oiling system, they do say there are differences in the head, pistons and block deck height.

One other thing I noticed was the AMC 258 i6 / 4.2l with a 2 BBL carb was first offered in 1977 in FSJ's , the cam for the 2 BBL was different from the 1 BBL. There were no specifics as to what the difference was.

 

[Rescue Diver]

I am looking at my 1977 FSM and there is no mention of a difference in oiling system, they do say there are differences in the head, pistons and block deck height.

One other thing I noticed was the AMC 258 i6 / 4.2l with a 2 BBL carb was first offered in 1977 in FSJ's , the cam for the 2 BBL was different from the 1 BBL. There were no specifics as to what the difference was.

I read that the old school valve train oiling system was used from the beginning of time to somewhere in the very early 70's around the time the AMC 258 i6 / 4.2l was first introduced. I would be surprised if your 77 FSM said anything about it.

Thanks for the info on the different cams. Been wondering if they were different. I wish someone would produce the cam specs. One thing I do remember reading was that the 1979 one and two barrels were both rated at about 110 hp. Of course that was also on the net, so it could be wrong.

I found the site again.

Jeep Engines - AMC 258 I6

Here's their article on the AMC 232 i6 . It doesn't say anything about the valve train being any different than the AMC 258 i6 / 4.2l . I'll have to search for the souce I got that from. This article does however say that they changed the bell housing pattern in 1971. I'd say if the guy asking about the AMC 232 i6 for a head swap has a 1972 or newer, the head swp is probably no harder than the AMC 258 i6 / 4.2l .

Jeep Engines - AMC 232 I6

 

[73CJ]

Nice setup! How much did the Holley FI run you?

And now for the big questions. How many miles have you put on it since you built it? How's the JB weld holding up? Any leaks?

Oh, and how are the cam gear and push rods holding up with that HEI and the 4.0 head???:grinjeep:

I got the Holley on eBay for $450. Super adjustable.

I've got 1300 miles on it. Most in the pasture, in the sloughs, hills and pulling others out. In other words -hard miles.

No issues with the JB Weld. I used water solvable peanuts and made the JB a 1/4" thick. No leaks. I was leery at first, but why mill the head after welding up the ports if not necessary with JB? I've used JB for 35 years - great stuff. It can fix things that will amaze you.

The cam gear show no sign of wear or slop. Timing has not changed in 1000 miles. Probably the best indicator. Starts real quick. No pumping the old 2bbl til your foot is pooped.

 

[Rescue Diver]

I got the Holley on eBay for $450. Super adjustable.

I've got 1300 miles on it. Most in the pasture, in the sloughs, hills and pulling others out. In other words -hard miles.

No issues with the JB Weld. I used water solvable peanuts and made the JB a 1/4" thick. No leaks. I was leery at first, but why mill the head after welding up the ports if not necessary with JB? I've used JB for 35 years - great stuff. It can fix things that will amaze you.

The cam gear show no sign of wear or slop. Timing has not changed in 1000 miles. Probably the best indicator. Starts real quick. No pumping the old 2bbl til your foot is pooped.

Well then, that makes two of us!

I did the JB Weld but I made it about 1/2" thick over the corn starch peanuts. It took one and a half JB weld kits to fill them. I have over 1,000 miles on the new head and no leaks. With over 5,000 miles on the HEI, my cam gear and distributor gear look like new. Some motorcraft distributor fanatics would have you believe that what we're reporting isn't possible, and that we must be lying.

The upgraded stock distributor and the HEI are both great setups, and will perform about the same when set up correctly. I just wish the other side wasn't so adamant about wanting everyone to join them that they would resort to making up things or exagerating the facts based on a few people that didn't do the HEI conversion correctly.

P.S. Sweet deal on the Holley FI!!

My MC2100 carb works great and starts very easy even in really cold temps without having to pump the gas a lot, but it probably doesn't perform as well or get as good MPG as your FI setup.

 

[73CJ]

It is pretty hard to measure HP but pretty easy to measure time.

That's what I do with the Nordkog CJ speedometer. It has the timer built in. Nice feature.

 

[73CJ]

Well then, that makes two of us!
We'll have to keep compare notes 6,12 months etc.

 

[ThisGuyUKnow]

I have been off the reservation for a while so I am coming into this thread late.

I too would like to see dyno results of just the 4.0 head on a AMC 258 i6 / 4.2l . That being said I think it is a must upgrade for any AMC 258 i6 / 4.2l .

I did mine in tandem with a junkyard mpfi mod and I ended up using all 4.0 serp components so I didn't have the same pump issues as others.

I have an extremely long thread on the whole install floating around here.

I definitely noticed a difference on the highway. I still have trouble on hills or when i am pulling a trailer but i think that is because of my 2.72 gears.

 

[Rescue Diver]

I have been off the reservation for a while so I am coming into this thread late.

I too would like to see dyno results of just the 4.0 head on a AMC 258 i6 / 4.2l . That being said I think it is a must upgrade for any AMC 258 i6 / 4.2l .

I did mine in tandem with a junkyard mpfi mod and I ended up using all 4.0 serp components so I didn't have the same pump issues as others.

I have an extremely long thread on the whole install floating around here.

I definitely noticed a difference on the highway. I still have trouble on hills or when i am pulling a trailer but i think that is because of my 2.72 gears.

How many miles have you put on it? What year AMC 258 i6 / 4.2l did you put it on? And last but not least, which push rods are your using? It would be good to get a basic list of what to use and what not to use that others can follow.

Wow 2.72 gears! What size ties are you running? Do you even use 4th gear? I was wishing I had some 4.10s, but yours make me glad I at least have 3.54!

P.S. Thanks for joining the new thread. I know when things are old news to some of us, we're some times reluctant to rehash it all. I just did my swap a month ago, so hearing about those that did this a while back and are still going strong is great!

 

[ThisGuyUKnow]

How many miles have you put on it? What year AMC 258 i6 / 4.2l did you put it on? And last but not least, which push rods are your using? It would be good to get a basic list of what to use and what not to use that others can follow.

Wow 2.72 gears! What size ties are you running? Do you even use 4th gear? I was wishing I had some 4.10s, but yours make me glad I at least have 3.54!

P.S. Thanks for joining the new thread. I know when things are old news to some of us, we're some times reluctant to rehash it all. I just did my swap a month ago, so hearing about those that did this a while back and are still going strong is great!

http://www.jeep-cj.com/forums/f2/4-0-head-mpfi-serpentine-my-82-258-a-5083/

That thread above is my write up all the stuff i mentioned. It's extremely long just as a forewarning and I am constantly updating as I go along and have new issues.

I have well over 2k on the head and 4.0 mpfi.
The block is an 82 and the rods I used were the original ones from the AMC 258 i6 / 4.2l .

I have 31s and with no trailer I can use 5th with trailer 5th is useless. With the mpfi and 4.0 head I did an ax15 swap as well. I am planning on swapping a set of wt 3.54s in. I looked at the grim calculator and think that ratio will be perfect

 

[TheDirtyCJ]

I had already upgraded my ignition with the great choice of an HEI when I first built my engine last year, so that stayed the same. I also stuck with the stock 1 barrel cam, which I believe is the exact same cam they put in 2 barrel engines from the factory. Someone please correct me with the actual lift and duration numbers if I'm wrong about that. I do know that the HP rating between the 1979 1 and 2 barrel engines were about the same at 110 hp. One other reason I don't believe the carb made any real difference is that on long uphills at highway speed with the 1 barrel carb before the head swap, it didn't really make any difference if I was at 3/4 throttle or full throttel, which tells me the engine just didn't have enough in it to use all of the 1 barrel. I'm noticing that even more with the 2 barrel with which I never floor it.

With a 4.0 head you get bigger valves, bigger better flowing ports, much higher compression(9.2 to 1 instead of 8.0 to 1) and a much better flowing exhaust manifold. All of those things other than changing cams are exactly what you would do to build a race engine, so there's no way you shouldn't see a serious horse power gain. Even with the same small cam, the engine will flow a whole lot better with the larger ports, and the bigger valves opened at the same lift and duration.

My seat of the pants comparison is more than just a feeling that it has more power and better MPG. It's a simple fact that before, I could not maintain 65 mph on hills and now I can do it easily, and it's a fact that before, I could only drive to work for three days on a tank of gas and now I can make about four trips on the same exact roads. This is an apples to apples comparison. The only other change I made was the carb, and I wasn't even using the whole CFMs of the old one barrel Carter because the engine couldn't make use of it.

It's the head that did it. Plain and simple.

I'm with you that I would love to see a before and after Dyno comparison. Most sites claim a 40 hp gain from the head. I haven't found a site that backs that up with actual dyno charts, but based on my results, I totally believe I gained that much. It's like night and day.

****EDIT****

I've swapped a whole lot of carbs in my life on a lot of different engines and vehicles 2 barrel to 4 barrel, quadrajet to Holley etc...) and I've never come close to seeing this kind of HP gain unless the old carb was not functioning correctly, and my old Carter was freshly rebuilt and working fine.

I am doing this swap right now on my 1983 CJ, I found a rebuilt 7120 casting its been decked and ported. I bought a Borla header and plan on using my Offey intake with Holley truck avenger 4 brl carb. As usual I'll post pics of b4 during and after. I plan on putting it on the dyno tomorow prior to the swap so I can give an assessment of HP improvement. Now remember I dont have to worry about emmisions so I already have pacesetter headers with the above improvements already mentioned. I have TFI juicebox ignition upgrade as well. So lets just see what happens! I'm getting excited and ready to get r done! Also I want to point out I am going strictly by Tim Weaver's 4.0 head swap article. Excellent read by the way. check it out.

 

[Rescue Diver]

I am doing this swap right now on my 1983 CJ, I found a rebuilt 7120 casting its been decked and ported. I bought a Borla header and plan on using my Offey intake with Holley truck avenger 4 brl carb. As usual I'll post pics of b4 during and after. I plan on putting it on the dyno tomorow prior to the swap so I can give an assessment of HP improvement. Now remember I dont have to worry about emmisions so I already have pacesetter headers with the above improvements already mentioned. I have TFI juicebox ignition upgrade as well. So lets just see what happens! I'm getting excited and ready to get r done!

So you're doing the 4.0 head swap, but you're sticking with the same intake and carb, and you're just changing from one header to another, so any performance gain you have will be due stricktly to the head? And you plan to dyno before and after????

You rock! It's about time someone did that!

I'm eagerly awaiting the results!

 

[TheDirtyCJ]

I am doing this swap right now on my 1983 CJ, I found a rebuilt 7120 casting its been decked and ported. I bought a Borla header and plan on using my Offey intake with Holley truck avenger 4 brl carb. As usual I'll post pics of b4 during and after. I plan on putting it on the dyno tomorow prior to the swap so I can give an assessment of HP improvement. Now remember I dont have to worry about emmisions so I already have pacesetter headers with the above improvements already mentioned. I have TFI juicebox ignition upgrade as well. So lets just see what happens! I'm getting excited and ready to get r done! Also I want to point out I am going strictly by Tim Weaver's 4.0 head swap article. Excellent read by the way. check it out.

AAAARRRRGGGHHHH!!!! Yoke broke on the way to Dyno Chip
I ordered the Ubolt design yoke replacement for the drive shaft and diff...I still will do this as soon as its up and running again! Stay tuned.

 

[Out of my mind CJ5]

[
Here's their article on the AMC 232 i6 . It doesn't say anything about the valve train being any different than the AMC 258 i6 / 4.2l . I'll have to search for the souce I got that from. This article does however say that they changed the bell housing pattern in 1971. I'd say if the guy asking about the AMC 232 i6 for a head swap has a 1972 or newer, the head swp is probably no harder than the AMC 258 i6 / 4.2l .

Jeep Engines - AMC 232 I6[/QUOTE]


the AMC 232 i6 is from a 75, do you all think that the head might be too big for the little AMC 232 i6 , i know its 3.8L but still just curious

 

[Rescue Diver]

the AMC 232 i6 is from a 75, do you all think that the head might be too big for the little AMC 232 i6 , i know its 3.8L but still just curious

I think AMC did away with the old school solid pushrod motors before 1975. As long as the head bolts are in the same locations, and you're willing to possibly have to deal with customizing some brackets(power steering and throttle linkage) I see no reason why you couldn't put a 4.0 head on a 1975 AMC 232 i6 . The only thing bigger about a 4.0 head are the valves. The ports are reshaped and raised to flow better. The combustion chambers are actually smaller than the AMC 258 i6 / 4.2l for higher compression. A AMC 232 i6 is just a AMC 258 i6 / 4.2l with a shorter stroke. I believe the AMC 232 i6 pistons are the same diameter as the AMC 258 i6 / 4.2l , so I'd be surprised if the head swap doesn't work just as well on your motor.

You lose a little torque with a shorter stroke, but you gain by having less rod angle so you can throw in a cam that's ground for higher RPMs than you might want to put in a AMC 258 i6 / 4.2l , to build more horse power on the top end.

I've built a few small block Chevy stroker motors over the years because I always like a lot of torque down low, but some guys prefer a shorter stroke high reving top end horse power engine. It's all personal preference.

A 4.0 actually has a bigger bore and a shorter stroke than a AMC 258 i6 / 4.2l .

The hot setup these days is to bore a 4.0 block .030 over, and install a AMC 258 i6 / 4.2l crank in it to make a 283 cubic inch stroker jeep motor. I plan to build this as my next motor. The really cool thing about it is, I already have the head and crank for it. All I have to do is get a good 4.0 block, have it bored, and buy a good cam and a new set of pistons!

I'll probably do this in 2012.

 

[ThisGuyUKnow]

I think AMC did away with the old school solid pushrod motors before 1975. As long as the head bolts are in the same locations, and you're willing to possibly have to deal with customizing some brackets(power steering and throttle linkage) I see no reason why you couldn't put a 4.0 head on a 1975 AMC 232 i6 . The only thing bigger about a 4.0 head are the valves. The ports are reshaped and raised to flow better. The combustion chambers are actually smaller than the AMC 258 i6 / 4.2l for higher compression. A AMC 232 i6 is just a AMC 258 i6 / 4.2l with a shorter stroke. I believe the AMC 232 i6 pistons are the same diameter as the AMC 258 i6 / 4.2l , so I'd be surprised if the head swap doesn't work just as well on your motor.

You lose a little torque with a shorter stroke, but you gain by having less rod angle so you can throw in a cam that's ground for higher RPMs than you might want to put in a AMC 258 i6 / 4.2l , to build more horse power on the top end.

I've built a few small block Chevy stroker motors over the years because I always like a lot of torque down low, but some guys prefer a shorter stroke high reving top end horse power engine. It's all personal preference.

A 4.0 actually has a bigger bore and a shorter stroke than a AMC 258 i6 / 4.2l .

The hot setup these days is to bore a 4.0 block .030 over, and install a AMC 258 i6 / 4.2l crank in it to make a 283 cubic inch stroker jeep motor. I plan to build this as my next motor. The really cool thing about it is, I already have the head and crank for it. All I have to do is get a good 4.0 block, have it bored, and buy a good cam and a new set of pistons!

I'll probably do this in 2012.

Good luck enjoying it when the world ends LOL

So is the decision that a AMC 232 i6 can match up to a 4.0 head?

 

[Rescue Diver]

Good luck enjoying it when the world ends LOL

So is the decision that a AMC 232 i6 can match up to a 4.0 head?

I suspect that a 4.0 head swap on a AMC 232 i6 would work as well as on a AMC 258 i6 / 4.2l because they're basically the same motor besides the crank, but I don't know for sure. I'd compare a AMC 258 i6 / 4.2l and a AMC 232 i6 head gasket to make sure the bolt holes line up, and go from there. As long as it bolts on, there's no reason I can think of why it wouldn't perform great on a AMC 232 i6 .

The world isn't coming to an end in 2012. We're just going to be invaded by Mayans that traveled far into the future to get more advanced weapons than we have now, and then back to 2012 to conquer us. Pay back is a real b!otch some times!

 

[ThisGuyUKnow]

I suspect that a 4.0 head swap on a AMC 232 i6 would work as well as on a AMC 258 i6 / 4.2l because they're basically the same motor besides the crank, but I don't know for sure.

Hmm now I want to see someone do a 4.0 injection swap into a AMC 232 i6 . That would be cool to see.