~ The Barnacle ~ [CJ-7]

[Jeep-Power]

Head shop

[Pete]

just throwing this out there!

http://www.edelbrock.com/automotive/...ads/jeep.shtml

[warthog_cj7]

Thought you were just getting it all dialed in.
Why head pull?

[Fuzzy]

Thought you were just getting it all dialed in.
Why head pull?

Ummm - as I recall, Pete has two less cylinders on one side, but another 4 on the other!

I am guessing that he was tantalizing Tall Peter. This is way too confusing with Peter posting in Pete's thread, and then Pete responding to Peter about his rig! Or, maybe I'm just out of it....

[warthog_cj7]

I was referring to the head pull on Barnacle, why pull?

[Pete]

So whats with the head pull?

[Jeep-Power]

well, it's bit of a story-

The flattening of the manifold gasket surface (above) worked well, but the fiber gasket is just not up to turbo duty-- apparently no matter how flat and true things are. Multi Layer Steel (MLS) gaskets are a modern fix for such problems. Unfortunately no one is making a MLS gasket for the OBD1/7120 heads. Only the 0331 head has am MLS manifold gasket available-- I even looked into getting one custom made for the 7120 head, but no luck. The only option is to 'upgrade' to the 0331 head, thus allowing the use of the coveted MLS gasket set. (even the manifold builder Boostwerks went through all this himself)

The 7120 head owed me nothing-- being a junkyard takeoff (with who knows how many miles on it) that I just dropped ontop of this engine approx 100k miles ago.


So I bought a 'rebuilt' 0331 head off Ebay for $250 plus shipping. (This includes the core return shipping charge, as well). They were happy to take the 7120 head as a core for the 0331 head. For the time constraint (need to drive this to THe COve Crawl in 3 weeks), it was the best choice.




The ports had a surprising amount of mold/casting flash that I just had to take care of-- have been grinding away and smoothing out all the corners for the past two nights.





The biggest challenge with a new head is blocking off the 4.0 water passages, again. The 4.2 block is a little different design, and the corner closest to the head bolt hangs over the block y just the slightest. With the 7120 head. I used water dissolve-able packing peanuts and JB Weld to seal them. THis time I am looking to braze in some steel. Boring the holes round and then filling them in with 3/4" freeze plugs and copper-silver braze (it flows really well).

[Fuzzy]

I'm still confused. You have a new head, with smaller exhaust ports, and a hump in the intakes (what's that for?), but you are machining your old head? Also, what the heck happened in the second to last photo? It looks like one of my welding attempts?

Also, are you gonna polish your intake runners? Looks like a pretty major casting line in them!

[Jeep-Power]

I'm still confused. You have a new head, with smaller exhaust ports, and a hump in the intakes (what's that for?), but you are machining your old head? Also, what the heck happened in the second to last photo? It looks like one of my welding attempts?

patience Larry-- I posted the pics with my phone an then logged in with the laptop to add the text. :)

[Fuzzy]

patience Larry-- I posted the pics with my phone an then logged in with the laptop to add the text. :)

Enquiring minds want to know!

[Jeep-Power]

Enquiring minds want to know!

I see that! :)

Before and after pics to come of the port smoothing

[Fuzzy]

ahhh - the text has magically appeared!

I'm still curious about the ports. The exhaust ports looks smaller, and the intakes have that hump, which looks like it is on the valve side. Is that "normal" or something for the turbo?

Finally, on your old head, it's very black around the exhaust ports. Is that because the gasket was failing, or at least leaking?

[Jeep-Power]

The smaller and higher exhaust ports have something to do with effeciency- IIRC, they produce a higher velocity on the exhaust.

The 'humps' are clearance for the injectors. The later head had a different manifold. The manifolds do interchange, but i guess there are subtle differences in the injector location.

Yes, that black is where it was leaking- pretty much everywhere. Smaller leaks than before flattening, but more of them. :p

[warthog_cj7]

Isn't the 0331 head prone to cracking?
But I think that only comes after an overheating issues.

That'll be a good fix, time consuming, but good fix.

[2000XJ]

The 0331 head was prone to cracking, but it didn't affect all 0331 heads. Typically if you made it beyond 60k miles you were in the clear. I have 110k miles on the XJ with the 0331 head and I overheated once or twice when working it hard and I have never seen any symptoms of a cracked head. I wouldn't stress over the possibility of it happening as it isn't that frequent.