4.0 on a 4.2 Options

[Cheepjeep85]

well i'd say you can still use the same intake but you would need a header or exhaust manifold from those years, if it would matter at all.

 

[Rescue Diver]

Guess what I was doing today??? I was unbolting a #7120 head from a 1995 Cherokee!

I only got it about half way removed because my 5/8" x 1/2" drive socket cracked and I didn't have time to go pick a new one up before the place closed. I'll head back there in the morning and finish the job. Now I just have to scrounge up an intake manifold for a carbed 1981 or newer 6 cylinder and buy the new exhaust manifold from ebay.

The only real disapointment is the machine shop is closed tomorrow. I was planning to drop the head off there for a valve job and resurface on my way home from the bone yard today.

 

[Sasquach]

Excellent

 

[Petescj]

I have one on my '85 parts Jeep. Located in Pa. though. If you dont find one closer shoot me a pm. I'll let it go for someone here since you need it but otherwise I'll keep it myself.

Now I just have to scrounge up an intake manifold for a carbed 1981 or newer 6 cylinder

 

[Rescue Diver]

I have one on my '85 parts Jeep. Located in Pa. though. If you dont find one closer shoot me a pm. I'll let it go for someone here since you need it but otherwise I'll keep it myself.

Thanks. I'll PM you.

 

[Rescue Diver]

Uh Ohhh! Look what Daddy did!

It cost me a whopping $44 for the complete head plus $6 for the valve cover from our local pick-n-pull. Add in $125 for a valve job and resurface and I really have no room to complain.

 

[Rescue Diver]

A couple more updates. I grabbed an intake for a 1980-1986 CJ AMC 258 i6 / 4.2l from ebay a while ago, and I also ordered a brand new exhaust manifold for a 4.0 from ebay for only $72 including shipping.

All I need now is a Motorcraft 2150 carb from a 70's ford truck and I'm set!

I would use the perfect carb that I'm now running, but it's only a one barrel so it won't work with the new intake.

 

[cavie98]

Hey guys. I've been following this thread and am about to do the head swap. I am looking at a 93 wrangler donor engine tomorrow to make sure the head # is the 7120. It will be put on a 78 AMC 258 i6 / 4.2l engine. I want to keep this one the cheep within reason. I know you have to spend some money to make it right. Just want to know where to spend and where to reuse parts.

I have read alot about this conversion and have a few questions. Sorry if these are repeat questions.

1. Can you use the same AMC 258 i6 / 4.2l intake if it is a 1bbl carb?
If so then I'll do that then upgrade. If not the what 2bbl intake should I get and what carb?
2. Can I use the same rods and arms? Should I get new ones?
3. New head bolts? 4.0 bolts or AMC 258 i6 / 4.2l bolts.
4. Any onther advice......

Sorry for the questions. I'm going to read some more articles.

Thanks in advance,

Dan

 

[Rescue Diver]

Hey guys. I've been following this thread and am about to do the head swap. I am looking at a 93 wrangler donor engine tomorrow to make sure the head # is the 7120. It will be put on a 78 258 engine. I want to keep this one the cheep within reason. I know you have to spend some money to make it right. Just want to know where to spend and where to reuse parts.

I have read alot about this conversion and have a few questions. Sorry if these are repeat questions.

1. Can you use the same 258 intake if it is a 1bbl carb?
If so then I'll do that then upgrade. If not the what 2bbl intake should I get and what carb?
2. Can I use the same rods and arms? Should I get new ones?
3. New head bolts? 4.0 bolts or 258 bolts.
4. Any onther advice......

Sorry for the questions. I'm going to read some more articles.

Thanks in advance,

Dan

Since your AMC 258 i6 / 4.2l is pre 1981, it'll take your stock size 1/2" head bolts. You'll want to fill the 12 water ports on the intake side of the head next to the combustion chambers either by getting them welded in, or filling them with JB Weld. You'll need to use an exhaust manifold from a 91-99 4.0, and your 1978 cast iron intake will be very hard to use if it's even possible. The flanges that hold it down to the head are much thicker than the flanges on the newer exhaust manifolds, which means they won't work together with the bolts and curved washers that mount them. I opted for a later model 1985 AMC 258 i6 / 4.2l aluminum intake. As far as a carb, most people go with a Motorcraft/Autolite 2100 or 2150 because they're simple, they're a dime a dozen, and they work well for 4 wheeling on steep angles. Use your stock AMC 258 i6 / 4.2l pushrods and the rockers that come with the 4.0 head.

 

[73jeep]

Hey guys. I've been following this thread and am about to do the head swap. I am looking at a 93 wrangler donor engine tomorrow to make sure the head # is the 7120. It will be put on a 78 258 engine. I want to keep this one the cheep within reason. I know you have to spend some money to make it right. Just want to know where to spend and where to reuse parts.

I have read alot about this conversion and have a few questions. Sorry if these are repeat questions.

1. Can you use the same 258 intake if it is a 1bbl carb?
If so then I'll do that then upgrade. If not the what 2bbl intake should I get and what carb?
2. Can I use the same rods and arms? Should I get new ones?
3. New head bolts? 4.0 bolts or 258 bolts.
4. Any onther advice......

Sorry for the questions. I'm going to read some more articles.

Thanks in advance,

Dan

You should use one of the later model water heated cast aluminum 2BBl manifolds. The cast iron one bbl is very restrictive, and REQUIRES manifold heat from the exhaust manifold which the 4.0L manifold doesn't have a provision for. Run whatever kind of fuel sytem you want, MC2100, Holly 2bbl , or TBI

Here a picture of the manifold... Thats a AMC 258 i6 / 4.2l head but it fits on the just the same.
You can see coolant lines that feed the manifold here, it goes in series with the heater core. Water pump -> Manifold -> Heater Core -> Thermostat neck
You can also my diy tbi on there aswell.

 

[cavie98]

You should use one of the later model water heated cast aluminum 2BBl manifolds. The cast iron one bbl is very restrictive, and REQUIRES manifold heat from the exhaust manifold which the 4.0L manifold doesn't have a provision for. Run whatever kind of fuel sytem you want, MC2100, Holly 2bbl , or TBI

Here a picture of the manifold... Thats a 258 head but it fits on the just the same.
You can see coolant lines that feed the manifold here, it goes in series with the heater core. Water pump -> Manifold -> Heater Core -> Thermostat neck
You can also my diy tbi on there aswell.

What year and which model jeep does the manifold your talking about come from?
What does the water heated have to do with it and how does that work?
I would also like to know more about your diy tbi setup. Very interested.
Sorry, I'm kinda new to all the engine work, and I'm trying to do it all myself. Just means I have to ask alot of questions.

Thanks for the help,

Dan

 

[Rescue Diver]

What year and which model jeep does the manifold your talking about come from?
What does the water heated have to do with it and how does that work?
I would also like to know more about your diy tbi setup. Very interested.
Sorry, I'm kinda new to all the engine work, and I'm trying to do it all myself. Just means I have to ask alot of questions.

Thanks for the help,

Dan

You can run an 80-85 aluminum intake. You plumb one of the heater hoses in and out of the intake is all.

I don't know much about what's available for TBI, but you can run a stock direct port injection system from a 91-99 4.0 and they're a dime a dozen. I just tossed a direct port F.I. intake, injectors and throttle body in the front seat of the cherokee I pulled the head from at pick-n-pull. They had two or three other 91-99 jeeps sitting around with all the parts you would need as well. The down side is you have to also use the under hood wiring harness and computer from donor vehicle, and you'll also need an electric fuel pump. I might do that upgrade eventually, but it goes against my keep it simple phylosophy. For now I'm just installing a 1985 intake and a motorcraft 2150 carb.

 

[cavie98]

Ok. I got the head from a '93 Wrangler. Now, I have found an exhaust manifold from a local guy for $50. It is from a '99 Cherokee. Will that work or do I need to find a year that is closer?

Thanks, Dan

 

[Rescue Diver]

Ok. I got the head from a '93 Wrangler. Now, I have found an exhaust manifold from a local guy for $50. It is from a '99 Cherokee. Will that work or do I need to find a year that is closer?

Thanks, Dan

Why pay $50 for a used exhaust manifold when you can buy a brand new one with the gasket, donut gasket and the flange bolts for only $72 on ebay including shipping???????

That's where I bought mine, and there was no catch to it. They sell the manifold for $67 and only charge $5 for shipping. When I ordered mine, it was on my door step in 4 days.

 

[cavie98]

Why pay $50 for a used exhaust manifold when you can buy a brand new one with the gasket, donut gasket and the flange bolts for only $72 on ebay including shipping???????

That's where I bought mine, and there was no catch to it. They sell the manifold for $67 and only charge $5 for shipping. When I ordered mine, it was on my door step in 4 days.

Do you mind hooking me up with the info for what you put in the search on ebay? That would be a great thing if they still have them. I know you did the legwork on the lookup. Just trying to get the right one the first time? You have been a huge help. Alot better than my so called jeep specialist that is local!!!!

I think I've found it. $67.44 plus shipping. Coming from AZ or VA. Seller---autoandart. Do you remember if this is the one?

Thanks, Dan

 

[Rescue Diver]

Do you mind hooking me up with the info for what you put in the search on ebay? That would be a great thing if they still have them. I know you did the legwork on the lookup. Just trying to get the right one the first time? You have been a huge help. Alot better than my so called jeep specialist that is local!!!!

Thanks, Dan

I can do better than that. The same seller has one listed again for the same price.

JEEP CHEROKEE GRAND WRANGLER EXHAUST MANIFOLD 4.0L 6CYL - eBay (item 230584123963 end time Mar-11-11 15:03:36 PST)

 

[cavie98]

That's it. Thanks for the info. I'll let you know how the progress goes once I get all the parts. I may have a few ?'s for you when the time comes, if you don't mind.

Thanks again,

Dan

 

[Rescue Diver]

That's it. Thanks for the info. I'll let you know how the progress goes once I get all the parts. I may have a few ?'s for you when the time comes, if you don't mind.

Thanks again,

Dan

Well I'm really only about one step ahead of you, but I'll be happy to share what I've figured out. I'll have it installed this weekend, so maybe at least I'll be able to tell if how noticable the difference is.

 

[cavie98]

Yeah, I'm right there with you. I plan on tearing into the donor 4.0 this weekend. I'll need to get the head work done.

It will probably take me a few weeks to get that done. There is a machine shop local, but the guy I talked to said they wouldn't do any work on it if the water jackets were filled with JB weld. They would have to drill and tap for freeze plugs, and they are not siue if they have the right bit and tap size. I am going to have to call around for a few other shops.

Just let me know how your project goes. Looking forward to it.

Thanks, Dan

 

[IOPort51]

The JB weld thing never made much sence to me as it gets soft at about AMC 150 deg. I see the need to ensure the hole does not extend past the edge of the block but I have never thought JB weld would have been my first choice.
Having done a bit of thnking on the matter I came to the conclusion that the orlando head was quite cost effective having been milled, valves ground and the holes welded closed.
How much was the cost of having the holes filled with freez plugs??