WJ Exhaust Manifold On 7120 Head

[DaveJeep]

Hey guys. I'm in the process of figuring out what I want to do when I build my stroker. I found a great deal locally on a 7120 head with me HD valve guides for only $200CAN so I might pick it up. I kind of want to use my 0331 head though because of the improved port design but I've been told not to and that it sucks.

So I am just wondering, will the WJ exhaust manifold fit the 7120 head? Are the ports on the exhaust manifold big enough to match up with the 7120 head?

Thanks guys.

[SilverXJ]

Personally, I don't like the way it fits. You would have to grind the exhaust manifold to match the exhaust port on the head so the exhaust isn't slamming into a wall on the way out. Hesco says it is doable and recommends using anaerobic sealant on the exhaust and copper high temp RTV on the intake instead of a gasket.

Another option is to get an after market header for the 0331 as I have heard they have larger ports that will work on the 0630 head.

Here are a few images to help you decide. The first one is a rubbing I did of both heads then overlayed them in photoshop. The red tinted one is the 0630 head. The rest are of a 0331 gasket on a 0630 head.

Also, what year is your WJ?

[DaveJeep]

My WJ is a 99 with 170,000kms on it. I know it's prone to cracking but I don't plan on porting anything so I won't have a lot of money tied up in it if I do stay with the 0331.

Can I use the stock rockers with the Comp 68-231-4 or 68-232-4? I'm on a tight budget. Also, does anyone run Comps valve springs & retainers? Will they work on my 0331 head? I don't know what else to ask right now.

[SilverXJ]

Since yours is a 99 I would highly recommend not using the stock head and either going with a 2003+ head. an Alabama cylinder head or a 0630 or 7120 head. I would just be afraid that it would crack.

You will be fine using the stock rockers on the cams. Comp Cam's valve spring setup won't fit the 4.0L heads as they are designed for the 258 head which uses an 11/32" valve stem and square lock slot. The 4.0L heads use an 8mm stem and rounded valve lock slot. Plus I feel that they are too strong.

Two valve spring options I know of are the Mopar Perfomance springs and lafrad's Crower beehive setup. The part numbers for those are in the Misc part numbers FAQ. You aren't limited to those though, but you will have to do some research on other options or your machine shop can help you on that. There was someone on Naxja that had another Beehive setup but he was stingy and didn't want to share his part numbers with anyone.

[dwg86]

I used a rugged ridge header for a 0331 head on my 7120 head. The header ports are bigger and will work on a 7120 head. I also had to have a hole drilled for the idler pulley and make straps for the coil pack.

[YJason]

FYI: If your upgrading your vale springs be sure to use a double roller timing set

[Plechtan]

Hey guys. I'm in the process of figuring out what I want to do when I build my stroker. I found a great deal locally on a 7120 head with me HD valve guides for only $200CAN so I might pick it up. I kind of want to use my 0331 head though because of the improved port design but I've been told not to and that it sucks.

So I am just wondering, will the WJ exhaust manifold fit the 7120 head? Are the ports on the exhaust manifold big enough to match up with the 7120 head?

Thanks guys.

Nothing wrong with a 0331 head if it ia a later one 2002 and up or so. It was the early ones that had the problems.

[mendelmax]

Just a little doubt here- the WJ has a triple groove valves, right? This won't let to use the old single groove locks.

Now the question is- can Mopar Performance springs be used with old, stock locks and retainers? Or must the valves be replaced to single-groove ones? I'm facing this problem currently, and I also don't know what to do.

[SilverXJ]

Just a little doubt here- the WJ has a triple groove valves, right? This won't let to use the old single groove locks.

Right

Now the question is- can Mopar Performance springs be used with old, stock locks and retainers? Or must the valves be replaced to single-groove ones? I'm facing this problem currently, and I also don't know what to do.

You can't use the retainers, but IIRC you can use the locks as long as they are the same degree as the retainers. I think the stock locks may be the same degree as the MP ones. I'm not 100% sure on that though.

If you are having a valve job done, it would make sense to get some new or used single groove valves and swap them in.

[StroktWJ]

I used a 7120 head on my 00 WJ, use the 99+ intake/exhaust gasket. If you use the Victor Reinz MLS gasket you cant trim the gasket and you will have port area blocked. You will have to use a paper style gasket like the Fel-Pro if you would like to fit the ports appropriately. I used the Victor Reinz MLS.