4.0 on a 4.2 Options

[cavie98]

Ok, I found a MC2150 carb. Now, I know a prev. post said that I would have to fab a throttle bracket for the holley carb. Do I have to do the same with the 2150? Any mods that I have to do to get it to mount up and run.

Another ?, did you guys that did the JB weld do it before or after the head job and machine work? Where did you get the bio peanuts?

Do you guys have any pics of how you modified the powersteering bracket. Just trying to get the ducks in a row so to speak before I start the project.

Sorry for the newb questions.

Thanks for the help. Dan

 

[Rescue Diver]

Ok, I found a MC2150 carb. Now, I know a prev. post said that I would have to fab a throttle bracket for the holley carb. Do I have to do the same with the 2150? Any mods that I have to do to get it to mount up and run.

Another ?, did you guys that did the JB weld do it before or after the head job and machine work? Where did you get the bio peanuts?

Do you guys have any pics of how you modified the powersteering bracket. Just trying to get the ducks in a row so to speak before I start the project.

Sorry for the newb questions.

Thanks for the help. Dan

Congrats on finding a carb! What size venturis did you get. It should have the number on the side of the body in a circle. It'll be something like 1.08, 1.14 or 1.21. Hopefully it's not the 1.21" because that's 358 CFM which is a little big for the AMC 258 i6 / 4.2l . The 1.08" is 287 CFM and the 1.14" is 300 CFM. I have the 1.14 and it idles and runs great, but I never need anywhere close to full throttle. If I push it to the floor, it doesn't accellerate any more, it just wastes gas. But I'm not complaining. The 1.08 is the ideal MC 2100 carb for the AMC 258 i6 / 4.2l .

You'll need a adapter to bolt it to your manifold. I think the MR. Gasket one is model #1934 if I remember correctly, but others have complained about this one because it requires you to use the large thick base gasket so it covers all gaps and doesn't have a huge vaccum leak. I had no problem with that because my carb kit came with that gasket.

Youll need to fab up throttle cable and return spring brackets. I cut the end off of my stock throttle cable on the pedal end and shortened the cable housing quite a bit so it's not all twisted around and won't bind. I just used one of those drilled bolt and nut cable ends you can get at the hardware store to put the end back on the cable after shortening it. On mine, the home made throttle cable bracket is really close to the brake master cylinder. I had to angle it in slightly to clear.

You can buy the bio degradable foam packing peanuts at Office Max. They get $10 for a bag that's about 100 times larger than you will need to do the head ports. If you were local, I'd give you some of my left overs. I did the JB Weld after getting it back from the machine shop. It doesn't leak a drop, and I'm confident it won't ever leak.

I had to cut the living hell out of the metal power steering bracket, and then I also had to grind a pretty large chunk out of the aluminum as well. It no longer has the long bolt that goes all the way through to tighten it down after adjusting, but with the front and back bolts really tight, it's not gonna move on me.

Good Luck! I'm sure you're going to love the improvement as much as I am!

 

[Rescue Diver]

The dead spot is fixed. It turns out it was neither of the things I suspected. It was due to the PCV valve I bought causing a big drop in vaccum. I switched back to the CJ PCV valve and it gained several inches of vaccum and it now runs even better. Since the CJ PCV is the skinny type, I'll have to shop around for one that's the same weight but that'll fit the grommet I'm using.

One update on this post. I switched back to the 1974 Monte Carlo PCV valve from the Jeep one because even though it causes a few inch drop in vaccum, it helps scavenge the minor blow by better. The accellerator pump setting was the main cause of my dead spot on going from idle to throttle. Adjusting the idle mixture to the lower vaccum did the rest and the carb is working fine.

 

[cavie98]

Congrats on finding a carb! What size venturis did you get. It should have the number on the side of the body in a circle. It'll be something like 1.08, 1.14 or 1.21. Hopefully it's not the 1.21" because that's 358 CFM which is a little big for the AMC 258 i6 / 4.2l . The 1.08" is 287 CFM and the 1.14" is 300 CFM. I have the 1.14 and it idles and runs great, but I never need anywhere close to full throttle. If I push it to the floor, it doesn't accellerate any more, it just wastes gas. But I'm not complaining. The 1.08 is the ideal MC 2100 carb for the AMC 258 i6 / 4.2l .

You'll need a adapter to bolt it to your manifold. I think the MR. Gasket one is model #1934 if I remember correctly, but others have complained about this one because it requires you to use the large thick base gasket so it covers all gaps and doesn't have a huge vaccum leak. I had no problem with that because my carb kit came with that gasket.

Youll need to fab up throttle cable and return spring brackets. I cut the end off of my stock throttle cable on the pedal end and shortened the cable housing quite a bit so it's not all twisted around and won't bind. I just used one of those drilled bolt and nut cable ends you can get at the hardware store to put the end back on the cable after shortening it. On mine, the home made throttle cable bracket is really close to the brake master cylinder. I had to angle it in slightly to clear.


I had to cut the living hell out of the metal power steering bracket, and then I also had to grind a pretty large chunk out of the aluminum as well. It no longer has the long bolt that goes all the way through to tighten it down after adjusting, but with the front and back bolts really tight, it's not gonna move on me.

Do you happen to have any pics of how you did all of this? That would be very helpful. If you don't that's ok. I just thought it might help me with some ideas.

On the carb, I'm not sure which venturies it will come with. It is direct from the manufacturer. I can order it from Advance Auto. I haven't ordered it yet beacuse it will only take a few days to get here when I do order it. I will ask about the venturies before I order it.

You've been a huge help. I'll make sure I post up how everything goes when I get started.

Thanks, Dan

 

[Rescue Diver]

Do you happen to have any pics of how you did all of this? That would be very helpful. If you don't that's ok. I just thought it might help me with some ideas.

On the carb, I'm not sure which venturies it will come with. It is direct from the manufacturer. I can order it from Advance Auto. I haven't ordered it yet beacuse it will only take a few days to get here when I do order it. I will ask about the venturies before I order it.

You've been a huge help. I'll make sure I post up how everything goes when I get started.

Thanks, Dan

When you order the carb, what car does advance say it's for? If it's for a 6 cylinder that's 300 cubic inches or less, it should be about the right size.

Here's a pic of the power steering bracket barely clearing the front tube of the exhaust manifold after cutting and grinding a lot of it away.

 

[cavie98]

It took us a while to find the right one, an 80's model Bronco with a 302. They don't have any specs on what the venturi size is. I'm calling the company that AA orders it from tomorrow. Hopefully I can get someone to get me the right info. If not I'm gonna hit a few junk yards around here. I'll let you know what I find out.

Thanks for the pic.

 

[Renegade]

I need some help!!! I am a new member and I have really enjoyed reading all these threads. I purchased an 82 CJ7 last fall and it has been sitting at a couple of different shops for most of the winter, finally I got a guy who is into Jeeps to help me out, he's not real happy with this project because we are starting from scratch. So here goes. The Jeep had a Holley 4 barrel and an Offenhauser Intake on it when I got it, I wanted to go back to stock so I sold them, MISTAKE!! So when my mechanic looked under the hood he quickly noticed it had a different head on it. It seems I have the correct head everyone is talking about in this post. It has the 7120 casting number on it so I assume it is from an 91-95 4.0 When I first drove the Jeep home it ran rough but never overheated from the 60 mile trip, so we are assuming they did a good job sealing the head, and the Jeep has good compression. So here is the question, I spoke to the guys at 4WD and they sold me the Offenhauser Intake OFF6257 and I purchased the Holley 4 barrel Carb from JC Whitney's 814368. I was so pleased, I took them to the mechanic and he started to line up the intake and said it won't line up. So here is my question can you guys look at the pictures and tell me the exact Intake and Carb I want to purchase. I do not need a ton of power I am just wanting to restore the Jeep and put a small lift and 33's under it. Not planning on wheeling more than logging roads so I don't need a lot of low end power. So do I need a 2 barrel carb? If so which one do you suggest (part numbers and suppliers would be appreciated for both the carb and the intake) I am not opposed to running with the Holley 4 barrel but I just need the correct Intake to run with it. I kept the exhaust manifold so I think I am good there, He said that did line up correctly. I will post a few pictures. The last 3 pictures are the parts I sold! Thank You for your help!!

 

[Rescue Diver]

I spoke to the guys at 4WD and they sold me the Offenhauser Intake OFF6257 and I purchased the Holley 4 barrel Carb from JC Whitney's 814368. I was so pleased, I took them to the mechanic and he started to line up the intake and said it won't line up.

That intake should line up. It takes a small amount of work and engineering to get it to fit. Hopefully your mechanic will be willing to do it and up to the task. If you look at your pic, you'll see the two lower holes that go over the alignment dowl pins on a stock AMC 258 i6 / 4.2l head. Then you'll notice the bottom of the holes are missing. That's so you can mount the intake higher to line up with the 4.0 head raised intake ports by litteraly just sitting the notches in the bottom of the intake holes directly on top of the dowl pins instead of sliding it over them. The problem is since the Jeep inline six engine's intake and exhaust manifolds are both held on with shared bolts and cup washers, you'll have to either get some much larger washers to bridge the bigger gap between them due to the intake being mounted higher, or better yet, make some metal plates with a hole drilled in them to replace the washers that will equally clamp both manifolds to the head. That's one of the issues you have to deal with when doing this head swap. When your mechanic pulled it apart, did he throw away whatever the previous owner rigged up to bolt them on?

 

[Rescue Diver]

I purchased the Holley 4 barrel Carb from JC Whitney's 814368. can you guys look at the pictures and tell me the exact Intake and Carb I want to purchase.

So do I need a 2 barrel carb? If so which one do you suggest

I found the Holley you listed on JC Whitney. It's a Holley 390 cfm. That's pretty much the best 4 barrel you can get for a AMC 258 i6 / 4.2l with an Offy or Clifford 4 barrel intake and that carb is not cheap. If you already have it and the intake, I would use them.

Holley Carburetor - JCWhitney

 

[Rescue Diver]

Renegade , here are a couple links you should check out that tell a lot about what's required to make a 4.0 head swap work.

Tim Weavers 40 Head Article

4.0 head swap - Louisiana Off-Roader's Forum

 

[Rescue Diver]

Renegade , here's a pic I stold from Jeepforum that clearly shows what a guy used in place of the manifold cup washer to bridge the larger gap from the intake being mounted on the higher 4.0 head ports.

 

[Renegade]

Thank You for all the Info Rescue Diver, it has truly helped. I went down and talked to my mechanic and he plans to work on it the first of this week. I just knew I had bought all the right stuff but he kept challenging me on the fact that they didn't line up correctly. I did show him the changes that needed to be made, and he said ok. The story of why I took the original intake and carb off was I was planning on restoring it back to stock. I had a different shop pull the parts and I sold them on Ebay not knowing the head was swaped to a 4.0. The mechanic that pulled them unfortunately passed away a week or so later. The owner of the shop was not sure of how to complete the project so he towed it to another shop for free. It sat there all winter until about 2 weeks ago when I got frustrated and he towed it to the current shop, the guy is well versed in Jeeps but has mostly worked on the newer ones (Fuel Injected) he also owns a muffler shop and it needed one of those badly the PO really butchered it. I will let you know how everything turns out, I feel really excited about it.

 

[Rescue Diver]

Well if this mechanic dies, I'd sell the Jeep!

Seriously though. I hope your new mechanic is willing to use a little creativity and do the engineering required. It's not that complicated, but most mechanics get lost when it comes to custom engineering anything.

Good Luck!

 

[IOPort51]

stick some to the top bucket of your radiator and see what kind of consistency it has at 180 -212.

Ok, you forced me to look it up because I really didn't think you could possibly be right with such a low temperature claim.

I feel more safe with my choice than ever. This is from the JB Weld web site. Can't get much more official than that!

J-B Weld Company - Frequently Asked Questions

"A: J-B Weld (Part # 8265-S, 8265, and 8280) can withstand a constant temperature of 500 degrees F. The maximum temperature threshold is approximately 600 degrees F for a short term (10 minutes). "

 

[Rescue Diver]

stick some to the top bucket of your radiator and see what kind of consistency it has at 180 -212.

Talk about a delayed response! You answered a post I made way back, just a couple days before I actually installed the head. I no longer need to test the JB Weld by other means. I've been testing it driving to and from work every day for the past month. It's holding up just fine. Thanks for the concern though!

 

[IOPort51]

I know it's too late for you but I thought of it as a message to posterity.

Talk about a delayed response! You answered a post I made way back, just a couple days before I actually installed the head. I no longer need to test the JB Weld by other means. I've been testing it driving to and from work every day for the past month. It's holding up just fine. Thanks for the concern though!

 

[Rescue Diver]

I know it's too late for you but I thought of it as a message to posterity.

It's always good to know what possibly might go wrong when choosing any of the countless options we all have in building every aspect of our Jeeps. I looked up every single piece of info I could possible find on this head swap and found plenty of people that went the JB Weld rout with success, and I didn't find a single one that reported a leak. I also went straight to the JB Weld web site and it clearly states that JB Weld can sustain 500 degrees F indefinitely, and even spikes to 600 degrees. My motor only runs at 180 degrees. That was enough for me. Since I could find no proof that this was at all risky, especially if done right, since it was much cheaper than having the machine shop weld in or machine the ports for freeze plugs, and also because with welding, there's always a greater chance of cracks forming near the welds, I chose to go the JB Weld way, and I don't regret it a bit. So far so good with about 1000 miles on it.

 

[IOPort51]

You really must forgive me, I have always been the kind of guy that likes to void warranties.
I try to avoid believing everything I read, hear and in some cases see. It has been my experience that J B weld @ 180-212 degrees F is about the same consistency of freshly chewed chewing gum. Perhaps the 600 deg. is the point that it goes liquid.
The head swap is a lot of work, I know I have done it, it also involves a fair % of your disposable income, You have every right to be proud of it, I know I am proud of mine. I am not suggesting that you lay awake nights worrying about your coolant blowing out all over the side of your block, I am sure you will be just fine.
Actually, thinking of it, the area that is available to leak is quite small at very worst, most certainly not the entire hole. I would believe it to hear that 99% of the time it is not even a possibility.

It's always good to know what possibly might go wrong when choosing any of the countless options we all have in building every aspect of our Jeeps. I looked up every single piece of info I could possible find on this head swap and found plenty of people that went the J B Weld rout with success, and I didn't find a single one that reported a leak. I also went straight to the JB Weld web site and it clearly states that JB Weld can sustain 500 degrees F indefinitely, and even spikes to 600 degrees. My motor only runs at 180 degrees. That was enough for me. Since I could find no proof that this was at all risky, especially if done right, since it was much cheaper than having the machine shop weld in or machine the ports for freeze plugs, and also because with welding, there's always a greater chance of cracks forming near the welds, I chose to go the JB Weld way, and I don't regret it a bit. So far so good with about 1000 miles on it.

 

[Rescue Diver]

You really must forgive me, I have always been the kind of guy that likes to void warranties.
I try to avoid believing everything I read, hear and in some cases see. It has been my experience that J B weld @ 180-212 degrees F is about the same consistency of freshly chewed chewing gum. Perhaps the 600 deg. is the point that it goes liquid.
The head swap is a lot of work, I know I have done it, it also involves a fair % of your disposable income, You have every right to be proud of it, I know I am proud of mine. I am not suggesting that you lay awake nights worrying about your coolant blowing out all over the side of your block, I am sure you will be just fine.
Actually, thinking of it, the area that is available to leak is quite small at very worst, most certainly not the entire hole. I would believe it to hear that 99% of the time it is not even a possibility.

There's nothing to forgive. You brought up valid points. I just weighed the facts that I could find, plus the fact that the gasket covers the holes and the block still baely covers the gasket, and decided it was pretty safe.

Happy wheeling!