Why "X" on x heads? History? Who decided to use an "X"?

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Just as the title says.

Why an "X" on X heads?

Thanks!
Kris
 
Great question.

I have three possible answers, but I am sure none of them are right;

1. So people would know they are X heads.

2. Because the letter A does not "mark the spot".

3. The letters O, J, U, & Z were reserved for later use.
 
so the X men could have heads for their cars...
 
It was the design of the head that named them X design. Made awesome H.P. for small block.Track tested and approved.
 
The "X heads" are early 340 heads and have an "X" that protrudes and is part of the iron casting.
 
From my understanding the casting letter was the engine plant where the engine was built in.I was told that by a chrysler engineer.He was a engineer so it could wrong. Mark
 
Everything the auto industry does is either for easy identification on the assembly line, or to improve an existing part.

In the first run or 2 of 340 cars there were NO 'X'es cast into the 2531894 head casting, which led to assembly line confusion between them and the 273/318 heads, so Chrysler added the 'X'es, as well as the 2 slash marks (ll) on the ends of the head.
Same reason a '489 case has a large "9" cast in it, as does a '742 a "2", to aid assembly line workers.
The difference between an X and an O, U, Z, and J heads are that some of the later heads were 1.88 intake AND the 3418915 head is cast with wider bosses on the lower row of head bolts.

Class dismissed and don't forget your iPods. :D

Mark.
 
Please teach some more.what was the X,O, U, Z, and J for.I think that was the question.I know that the engines were assemble at one plant in 68 but 69 and on they were assembled at other plants as well.Iam not being smart I am interested in this also. Mark
 
dartcuda1 said:
That was funny:notworth::notworth::notworth:
Click to expand...

I have a set of X heads that are being ported for my 416 right now that I probably paid good money for, for no good reason as my current motor had O heads on it right now. I do like the fact that my 68 formula S will look like it has original heads. I have seen many people write about X heads and J heads. What exactly are the O heads? Are they just J heads from a different run? What motors did they actually come on? At one time I was told that most of the O heads were six pack heads along with some of the J heads and they had offset pushrods to all clearance in head porting. Is this true or are they just another run of heads that are the same as J heads and came on 340's and 360's for many years? Just curious.
 
U, J, O are all the same basic 360 heads that came from different foundaries...

i believe my 6 pak heads are either O or U...have not looked recently...but again...they are same head with intake pushrod drilled at angle....
 
michformulaS said:
I have a set of X heads that are being ported for my 416 right now that I probably paid good money for, for no good reason as my current motor had O heads on it right now. I do like the fact that my 68 formula S will look like it has original heads. I have seen many people write about X heads and J heads. What exactly are the O heads? Are they just J heads from a different run? What motors did they actually come on? At one time I was told that most of the O heads were six pack heads along with some of the J heads and they had offset pushrods to all clearance in head porting. Is this true or are they just another run of heads that are the same as J heads and came on 340's and 360's for many years? Just curious.
Click to expand...
The six pack head is the only differant head with the pushrod holes moved for better porting.They made a revised head but put the pushrod holes back in the standerd location.These are the heads I think you ars talking about also they had the small valves.The mopar engine has all the info on this stuff.If I were to build a small block again I would just put a set of eddys.For the price and If you wanted to do porting It,s just cheaper. Mark
 
70aarcuda said:
U, J, O are all the same basic 360 heads that came from different foundaries...

i believe my 6 pak heads are either O or U...have not looked recently...but again...they are same head with intake pushrod drilled at angle....
Click to expand...

Thanks, I have searched for a couple years on what exactly an O head is but never could get a good answer.
 
Mark Nixon said:
Everything the auto industry does is either for easy identification on the assembly line, or to improve an existing part.

In the first run or 2 of 340 cars there were NO 'X'es cast into the 2531894 head casting, which led to assembly line confusion between them and the 273/318 heads, so Chrysler added the 'X'es, as well as the 2 slash marks (ll) on the ends of the head.
Same reason a '489 case has a large "9" cast in it, as does a '742 a "2", to aid assembly line workers.
The difference between an X and an O, U, Z, and J heads are that some of the later heads were 1.88 intake AND the 3418915 head is cast with wider bosses on the lower row of head bolts.

Class dismissed and don't forget your iPods. :D

Mark.
Click to expand...

Where did you learn that? A buddy of mine is gonna love this. His dad said he worked at the plant and was there for the confusion. He ordered that the "X" be cast in to eliminate the confusion. My buddy told me this a couple weeks ago after he was told that there was "X" heads on ebay for sale and it seemed to be a big deal.

Interesting stuff. Thanks for the help peeps!!!
Kris
 
dartcuda1 said:
Please teach some more.what was the X,O, U, Z, and J for.I think that was the question.I know that the engines were assemble at one plant in 68 but 69 and on they were assembled at other plants as well.Iam not being smart I am interested in this also. Mark
Click to expand...

In the case of all of the 3418915 related castings, I think it's possible there was a foundry/vendor issue and the casting letters actually represented the different foundries involved.

I have yet to see a 1970 340 that was assembled at a plant other than the Windsor engine assembly facility, coded as "FW340...."

I am a 340 FANATIC, plus I try to pay attention to some of the subtleties of them.

In truth, the real reason "360" is cast into all of the 1970-'72 "3418915" heads, aka O, U, Z, and J heads, is that in fact the 360 was intended to be a new-for-1970 introduction, a "factory small block stroker" like Chevy's 400 in '70, and, in fact, the 360 actually did make it into production in April or May of 1970, according to a TSB I have seen on the engine.

As far as I can tell, from having seen numerous, numerous 1970 340s, the 'X' head was a very early to as late as mid-January of '70 production, then the 'U' head hit assembly in, as far as I can tell, mid-January, until roughly March, then the 'O' and 'Z' heads kind of merged until about June or so, with the 2 styles of 'J' head casting, the full 'J' head and the one with a 'J' on top and an 'O' on the underside, with the last run of '70 having mostly 'J's.

Another curiosity, in 1971, from March-on, 340s were actually painted blue and I've known of 2 A bodies that slipped through with 'X' heads factory installed, possibly due to phasing out the 2.02 stock on the assembly line.

Yet another oddity, besides the T/A block, there was another variance on the 340 block in 1970, for a total of 3 possible production 340 blocks in 1970.

It has to do with the valley/deck supporting the head.
The late blocks (T/A included) have a point of casting right above the upper center bolt hole, inside the valley area. My best explanation for it is the same reason the '915 small block heads have the wide lower bosses, strength to help sealing.
The best way you can see the difference is to look at a '69 block and compare it to a '71 block and the difference jumps right out at you.

Mark.
 
Might be a dumb question but I just picked up some 318 heads with 675 and X cast into them. these aren't anything unusual are they?
 
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