1968 Mustang Fastback GT-390 X Codes Why So Rare?

[1968FASTBACK]

Mustang X Codes are rare... with only 733 built between all 3 body styles (477 hardtop, 189 fastback and 67 convert) they don't show up for sale very often, but are they only rare because no one in their right mind back in 1968 ordered a 390 2V X code when you could buy a 390 4V S code?? Most Mustang books do not even mention the X code version... I reckon the first thing most X code owners did was replace the carby and manifold with a 4 barrel so the 390 could get some air and fuel inside!! The car in the link below sold for US$45K I was told by the owner...

http://www.carsonline-ads.com/colsite/col?use=UC3_ViewPosting&cmd=showPosting&postingID=54672

[GLENN 70]

Only rare because they were not big sellers ,most people that wanted a fast mustang and a big block went for the most HP engine which was the S code 390 4v ,other than the 68 with the 428 CJ that was to dear . Its a bit like a 289 C code to a 289 A code ,most people went for C code ,but if you wanted a big block you wanted it to go .I think the compression ratio may have been less also .

[shaunp]

I think Mert on this forum has an X code.

[tim_morrison82]

The cj came out in late december 67, so until then the s code was still the biggest engine you could order (thats almost halfway through the 68 production run.)

[mert]

Yep, an X coupe.  But it is being "revised".    Did not have the original engine or trans, which made the mods easier.

On the comment about most who bought swapping to a 4V, kinda like saying most who bought a C code swapped it to a 4 bbl.... surprisingly a car with a 2v carb will actually move under its own power...   

They were a lower compression ratio, same C8AE-H heads, different valve springs, different cam, not sure about pistons...  rated at 280-ish HP vs the 325 for the 390GT,but still a hefty 400 lbft torque at 2600 rpm..
 vs ~425 @3200 for the S code...

Seen a few, most were still 2v's.  The engine was an early harbinger of things to come with insurance companies and the "feral gummint" starting to crack down on high hp cars....

http://www.ponysite.de/x_code.htm

http://www.remarkablecars.com/main/ford/ford-00267.html

[mert]

The 428CJ was not available in a Mustang until April 1, 1968.... at about $450, a big bump on a ~$2700 base price car!  and another $250 for a 4 speed...

The 390 was about $250, so the 428 was a big jump.  Think a $40,000 base car, and a $6,400 engine upgrade option in today's terms... siginificant.

 Have not seen a price on the X option... maybe I'll order a Marti duplicate window sticker, it would show it...

[shaunp]

CJ would have had a Bullnose top loader, that would explain the extra cost for the box perhaps.

[GLENN 70]

As far as i know the 390 x code was rated at 280 HP ,motor was out of the thunderbirds ,but there HP rating was 265/275 i think . As far as i know the intake had a T on it . There are so many stories on these x code engines ford doesnt even know ,just 390 2 v intakes some people say .

[mert]

The X code was not used in Tbirds, that was the original base 390 in the mid-60's, modified for Mustangs  (and Cougar/Fairlane/Montego) as the S code.  In 61-63 the 390 was the base (and only, in '61) engine for the Tbird!

The M code 390 was used in Tbirds in 62-63,  simialr Z code in Galaxies/Mercury's in 61-62.  P code (police interceptor, PI) 63-65 in Galaxies/Mercury's and Z code 61-63 Galaxies/Mercury's/Tbirds ('62)

The Y code 390 was also used, but I don't have references to dates or specific models.

So the 390 was common in Tbirds (thus the use of the term Thunderbird Special in some Ford literature for Mustangs w/390), but not in X livery...

The X never went in Tbirds, and was used in Cougars, Mustangs and some Mercury's starting in very late '67...and only used in 68.  The detuned 390IP (still an S code) replaced it and the earlier 390GT S code variant in 69...

[1968FASTBACK]

This X code fastback sold on eBay a few months back... looks like a nice well optioned car for US$23,100

http://cgi.ebay.com/ebaymotors/?cmd=ViewItem&_trksid=p3984.m1423.l2649&item=251099326412&sspagename=STRK%3AMEWAX%3AIT#ht_1522wt_708

[Macka]

I can imagine if someone owned one of these it would be the first thing they did was get rid of the 2V setup.   It would power up like a 4V V8 with two plug leads off.

[brent65]

Good page about the 390's here and the 3 versions that were around from 1966 onwards which goes into the 2 worth owning and how to build them up with genuine FoMoCo race program parts from back in the day, however it may rain on mert's 280HP aspirations :)

http://www.woodyg.com/fairlane/finfo/390intro.html

[mert]

Not aspiring to anything, just quoting Ford's rating for the 68 X code (premium fuel variant, not the base 2V's noted on Woody's site, but a lot of good FE info there). 

[mert]

.... the comment in the link on the 390GT and 428CJ using the same valve train is incorrect.

428CJ's used an Intake valve diameter of 2.082 - 2.097 inches and Exhaust valve diameter of 1.645 - 1.660 inches (think that's the same as many 427's) , where the 390 was 2.022-2.037 Intake and 1.551-1.556 Exhaust. 

As noted, the cam was the same...

[brent65]

Easy mert it was tongue in cheek, anyway the GT3904v, the 428 police and the 428 CJ all share the same valves, the 3902v and 3904v have the smaller valves. Of note however is the 428 police had both sizes of valves listed in it's repair specs, they also run 44degrees valve angle on both intake and exhaust where as the 390's and CJ's run 29 in and 44 exh.

[brent65]

Another good link regarding Ford cylinder heads can be found here, http://mustangtek.com/heads/Heads.html where you will find that the GT390's in some years even shared the exact same heads as various models of the 428CJ's

[mert]

No, they did not.  That site is a nice reference but full of errors.

The 428 noted on Mustang Tek for '68 GT500's and 390's is a 428PI, not a CJ.  Different engine, different heads.  Thus the change to GT500KR from GT500 in mid '68 when the Cj's came out.  The 67's used small valves in both the 390 and 428 (non CJ in 67) on a C7AE head very similar to the C8AE-H.

The stock '68 390GT heads used smaller valves than 428CJ's.  C8AE-H for the 390, an average head at best, vs the high performance C8OE-N for 428CJ's.  The reference on MT to the use of the C8OE-H for 428CJ's is also dubious...  see:

http://www.428cobrajet.org/id-heads

Most likley based on a typo in a shop manual or other promo literature (like some Ford docs noting 427's for '68 Mustangs, never happened)

Some early 390HP's (never used in a Mustang) did use larger valves, but not the 67/68 S code 390GT or the 69 S code 390IP used in Mustangs... totally differnt valves to a 428CJ.

And if still want to believe it, I have two pairs OEM '68 390 C8AE-H's I will be more than happy to sell for 428CJ prices.... heck, I'll sell 'em for half of the price of real CJ heads! 

[brent65]

Firstly I didn't realise we were discussing solely 68 engines but anyway I will leave it here as clearly you are right and every site I have read or use for information is full of errors but yours are all obviously correct . Thanks for the offer on the heads but I don't require them if I wanted more performance I would use ali heads not boat anchors.


C8OE-6090-H

14 bolt exhaust

68-69 390 GT Mustang
early 68 428CJ

Valves 2.08 / 1.65"
In port (1.94 or 2.34) x 1.34
Ex port 1.84 x 1.28
72.8cc

C8OE-6090-N is known as the correct 428 CJ heads. Period documentation often shows C8OE-6090-H heads as also being correct for CJ application.

 C8OZ-6049-J

and if you click the little green tick you will get this little piece of information:

Confirmed Application.
The application information provided has been double checked with at least a second source and confirmed as being 
100% accurate. Additional applications or application information may still be added as this new information is confirmed.

[brent65]

Also my S code 69 Mach 1 has a GT3904V not a 390IP would you like too see the marti report and build sheet or did Ford get that wrong as well?

[GLENN 70]

The question was why are x codes so rare ,because they did not make thousands . They were 2v not s code 4v ,who cares what they had inside and who really knows ,ford and other makers did strange things back then . Its like saying why is a falcon xw GT big block so rare ......

[mert]

Agree.  Rare because it was a high dollar, "lower" performance big block, as a first cut to meet coming emissions standards, rising insurance costs for "power", and a federal government making noises that it would be making it harder for the muscle era to continue.  An experiment, which failed to make it...

On the head issue (a threadjack, yes) Just trying to counter some bad info.  As it would be sad if some novice reads that a 390 head and a 428 CobraJet "are the same" and buys a "correct" C8AE-H or C8OE-H for a 428CJ build.  On the -H I'll side with the 428CJ forum (frequented by many known 428CJ/SCJ experts like Joe Sikora, Royce Peterson, Chris Teeling, etc) and many other documents/groups that dismiss the anecdotal "evidence" of either as correct for a 428CJ. 

Similarly, one could print a page of the '68 shop manual to "prove" 427's came in Mustangs.  The mythical "W code". 

There is a lot of bad info, in print, some provided by Ford as not all their docs are correct.  The main point is to do research, not blindly believe one website.  Especially for high-dollar parts.

If some prefer to believe Mustang Tek (as noted a nice reference site) and a green tick (verified by a whole "second source" ), that is their perogative.

However, based on suspect info, if somone paid $1000 (going price for correct -N 428CJ heads) for a pair of $200 ones I think it would be unfortunate.

And on "who cares about whats inside", the concours/correct restorer. Which admittedly, is rare here... as most here just want a car that kinda looks like a Mustang.  Which is fair enough, their car, their money. 

[mert]

"would you like too see the marti report and build sheet"

Please. 

Every Marti for a 67-69 S code I've seen (only mine and a few dozen from the old S code forum registry and the GT/CS site, a few other strays) just call out "390-4V" no distinction.  Kevin Marti confirmed this to me...

And the 68 and 69 build sheets I've seen have a single column for Engine and only note base Type (S, R, F, C, T, etc) and also the Tag Number to ID the engine specifics above the basic code (e.g K281S, 424T, etc, a complex coding accomodating carb, transmission, manufacturing plant, year, etc...26 variants in '69 so too detailed to list here, 8 pages in the Marti Tag book outline it)... or space for a longer call out like 4V390GT.

Would be very interested to see if there are different variations.

[brent65]

To all please note Mert's information is correct, my information was wrong and from dubious sources and you all have my humble apologise if I have mislead or confused anyone. Thanks Mert.