Head Dificulties

[Mack4194]

I`ve got an 89 longbed 4wd. 4.0. Here's the deal...

 

I had almost no compression in 2 and 5 was dead. I got a good deal on a head from an 88 that was completely refurbished but never installed so I snagged it up. Took my old head off on Sat morning, lower end seemed to be ok. I went out this afternoon to put the new head in. Compared them to each other and well... they're different. Got the numbers. My old head is a 2686 (I thought it was 2688 but aparently those don't exsist) My new head is a 3661. All the research I've done says mine came from an 88 YJ 4.2 CARBURETED!!!

 

Here are all the head numbers I could find in no particular order

 

New Head Numbers: 3661 F NH-1 88 C29

Exsisting Head Numbers: 2686 90 NH-2 E08 CN

 

So my simple question to you fine folks is should I just try to sell this one and get what I need, is there a not so hard way to make it work, or does it provide me the possibility of some sort of upgrade?

 

My initial thought is sell and buy again, but I thought it was worth an ask.

 

 

Thanks for your knowledge and time,

 

Mack

[ftpiercecracker1]

That head won't work with your 4.0 intake, you will have to sell and find another. I believe the head off of an HO will be the best path for you, better flowing head but will still be a direct bolt on for your intake manifold. But if you want to be 100% sure the next head will be the right one get it off of an MJ/XJ between the years 87-90

 

How do you know your head is bad? Obvious crack? Could be just a head gasket.

[mountainman]

Yeah have the machine shop rebuild your head and boom... good to go.

[cruiser54]

That head won't work with your 4.0 intake, you will have to sell and find another. I believe the head off of an HO will be the best path for you, better flowing head but will still be a direct bolt on for your intake manifold. But if you want to be 100% sure the next head will be the right one get it off of an MJ/XJ between the years 87-90

 

How do you know your head is bad? Obvious crack? Could be just a head gasket.

 

The difference in power produced by the 2 heads is only at the upper end of the RPM range. Torque is the same.

 

An HO head can be used o a Renix if you use the intake/exhaust gasket for the Renix so you won't have vacuum leaks. I have done this 3 times with excellent results. I did however match the ports of the intake manifold and the head to the gasket. Not really necessary but I had fun doing it.

[Mack4194]

Thanks guys. I figured as much. I just didn't have any head gasket symptoms (other than two no go cil's), and the gasket looked good as new when I pulled it off so I thought valves for sure. Still you never know it could've been seeping around something, and the valves didn't look bad to the naked eye either.

 

I hate the guessing game! I'll reply to this when I figure it out.

 

Know anybody that want's a rebuilt YJ head lol?

[ftpiercecracker1]

The difference in power produced by the 2 heads is only at the upper end of the RPM range. Torque is the same.

 

An HO head can be used o a Renix if you use the intake/exhaust gasket for the Renix so you won't have vacuum leaks. I have done this 3 times with excellent results. I did however match the ports of the intake manifold and the head to the gasket. Not really necessary but I had fun doing it.

 

Thats good to know for me because i will be using a 99 7120 head, but retaining the Renix exhaust manifold. If i understood correctly no matter what head you use you need the gasket that matches the manifold? Ex. HO head + Renix Manifold = Renix exhaust manifold gasket

[cruiser54]

Thats good to know for me because i will be using a 99 7120 head, but retaining the Renix exhaust manifold. If i understood correctly no matter what head you use you need the gasket that matches the manifold? Ex. HO head + Renix Manifold = Renix exhaust manifold gasket

 

Exhaust ports are identical Renix to HO. It's the intake ports that are slightly different. Use the gasket based on which INTAKE manifold you're using.