Mystery XX's scratched on rear of block Pictures

[alhs06]

Hi guy's,
Anyone out there familliar with the two XX's scratch welded onto the back of my block, it also has a #17 on the opposite side of the XX's.
The engine/block cast is C1AE 6015G, but I'm pretty sure it's not a 61 T-bird/Galaxy engine. It also has the extra (2) threaded "Blind" bolt hole just above the passenger side oil pan, a "28 DIF" stamp driver side block, (which I understand to be a Dearborn 428) along with a single "S" stamp on the underside of the side oil filter adapter see pic.
Hope the pictures are of some interest, The engine is sitting in my Beautiful but totalled 56 f100. When I bought the truck 2 (+) years ago, it was advertised with a 428 Cobra engine, & the seller was a reputable restorer in Orange County Ca. But that don't mean a darn thing anymore, I know...


oiler
block
head
manifold
Anyway, thanks for any help from all you guy's & gals too.
My user picter is my new 56 f100

[Mark IV]

Exhaust mainifold is 1963-64 thunderbird LH (uses a donut to seal to H pipe, 61-62 used a flat gasket)

Block casting number and date indicate a 61 block, the 65 engineering number, 64 casting date intake is probably just a mish mash configuration. A little bit of creative boneyarding probably created the combination.

Does the block have an alternator mounting boss cast into the RH front side? Only some very late 62 390s going into alternator try out on 1962 late build T Birds had that, otherwise the alternator boss did not appear until 1963 production and a C3 casting code.

[alhs06]

Kinda had the codes figured out, but thanks for the response, What I'm really curiouse about are the two XX's & the "S" stamp @ the oil filter. Any suggestion's on those item's. It's a toughn one, as I know the scratch welds always meant something out of the ordinary casting codes/serials, that's why they put them there. An "A" was for the Police interceptor, a "C" was for the cobra, a nothing was for the 390fe, but the XX's & the single 17
Thank's
police interceptor scratched "A"

common stamp for cobra engine @ oil

[elmariachi]

Were any engines really cast especially for Shelby? Based on the stories I have heard, Shelby bought finished engines and casted blocks as-needed from Ford; none were purpose-cast just for him. Has ever a 427 or 428 surfaced in a real Cobra that is dramatically different than any other high performance 427 or 428 to support this notion?

[alhs06]

All I know is that ford built the blocks for the racing team in the same plants they built blocks for the public, and they did have some pretty crude way's of ID'ing them. I do know that they had purpose for scratching mark's on the block's though & found out the "C" was for Cobra, the "A" was a Police Interceptor & the XX was for I don't know? I have emailed & asked around a little, but so far my question's haven't found the right person yet? Patience is a virtue..........isn't it? The fun is in the journey, I mean how many times do you get to search out a mystery in life, that's actually fun?

[elmariachi]

Originally Posted by alhs06

common stamp for cobra engine @ oil

Where are you seeing a "C" in this pic?

[alhs06]

Sorry for any confussion, the "C" is scratched on rear of block, where the "A" is in the other pic.

Some cobra blocks were only stamped in the oil filter area, this helps in ID of type of block. Here is an excerpt of an article I found, I have two other similar articles by different publication's, but this was the best one.

An FE block's casting date can be found just below the oil filter adapter on the front driver side of the block (see below). Casting dates follow typical Ford convention with the first character (a digit) representing the year, the second character (a letter) representing the month, and the last one or two characters (one or two digits) representing the calendar date in the casting month. The block in the picture above has a casting date of "9J15", which translates to September 15, 1969 -- early in the 1970 model year. Keep in mind that Ford first introduced the 428 Cobra Jet in April, 1968 as a mid-year option during the 1968 model year. There were earlier prototype and drag cars produced during calendar year 1967, so it's fairly safe to assume that block casting began no more than a few months in advance of production. Again, there are no absolutes here, but if the block you're looking at has a casting date in mid-early 1967 or earlier it's probably NOT a 428 Cobra Jet block. It MIGHT be a 428 Police Interceptor block, though.
Thanks to Dave Schouweiler for his contributions on this page.
Home
© 2009 Scott A. Hollenbeck. All Rights Reserved.

full article found here> http://www.428cobrajet.org/id-block.html

[wideglidejoe]

When we are talking about "C"s on the rear of a block meaning it was for a Cobra, aren't we talking about engines called Cobra Jets and Super Cobra Jets, not Shelby/AC Cobra cars? The Cobra Jet & Super Cobra Jet engines were in Mach I's, Torino Cobra's, etc. I thought that was what the C's were for. Please correct me if I'm wrong.

[alhs06]

I think your corect WGJ, below is a excerpt from Mustang 428 Cobra Jet Registry 1968 - 1970 Ford Mustang 428 Cobra Jet Registry!
found @ this link: http://www.428cobrajet.org/id-block.html
But aren't these the same engines used in the Shelby? That's what I understand, that they used the same cobra engines?

If you have access to the rear of the block, the most definitive method for verifying that you are looking at a reinforced 428 block (as used in most 428PI, 428CJ, and 428SCJ applications) is to check the rear face of the block for a scratch mark manually installed at the foundry which roughly reads "C"; see above photos. If the marking is an "A", it suggests you're looking at a standard 428 block as used in LTDs, Thunderbirds, and Mercurys. Shortages in 1968 sometimes caused the engine plant to substitute an "A" block for a "C", or vise-versa, so the presence of an "A" block is possible in a stock CJ engine. SCJs typically only received "C" blocks because the "A" block was discontinued from service toward the end of 1968. If there is no marking on the rear, it is most likely an ordinary 360/390/410 block. Since the scratch marks are year-dependent, you must verify that the block's date code shows it's of 1966 vintage or later. I've received reports of "C" blocks being cast as early as November 1967. Note also the three oil gallery plugs above the rear cam plug. All 428 Cobra Jets were originally equipped with hydraulic camshafts. If you don't see all three screw-in or press-in plugs you can bet that the block was originally equipped with a solid lifter cam and is not a CJ or SCJ block.

The following excerpt is from this link: http://www.kitcarusa.com/kb.php?aid=38

AC agreed, provided a suitable engine could be found. It was, in the form of Ford's 260 in³ HiPo (4.2 L) engine - a lightweight, thin-wall cast small-block V8 tuned for high performance. In early 1962, the first engineless AC Ace was air-freighted to Shelby's Los Angeles facility, where it was fitted with an engine and transmission in less than eight hours and taken out on test. Carroll Shelby claims the name "Cobra" came to him in a dream, and the car was given that name.
It proved to be a great performance success; the automobile had originally been designed by Shelby with the intention it would be a "Corvette-Beater" and at nearly a ton less than the Chevrolet Corvette, the lightweight car did just that. Production proved to be less easy; the AC chassis needed extensive work to take the Ford drivetrain, and at first, the cars were slow to be produced. Soon, a larger but similar Ford engine, the 289 in³ (4.7 L) V8 was fitted. Shelby Cobras began an extensive racing career with this engine, which boosted power from 165 to approximately 270 hp (123 to 201 kW) and gave it a new top speed of 140 mph (225 km/h).
1964 saw an even larger engine fitted; Ford's famed 427 in³ racing engine (7.0 L) developing 485 bhp (362 kW) and attaining a top speed of 163 mph (262 km/h). Even more extensive rework of the AC design was needed to accomplish this; the big-block FE-series engine was much too large to fit in the standard engine bay. The front tires were moved outward, with extended wheel-arches to cover them, and a new coil-spring suspension was designed.
Some Shelby Cobras were fitted with Ford's 428 in³ (7.0 L) engine, a less powerful engine despite the nominal increase in displacement, intended for road use rather than racing.

But still, my original question stand's..."Does anybody know what the XX scratch marks @ the rear of the block & the cast 17 mean, or the "S" stamp @ the oil filter area?

[Learjockey1]

My source is High Performance Ford Engine Parts Interchange, SA Design Publication, SA 56 by George Ried. I got it from one of the book stores. On page 91, they reference FE blocks with an” HI” and a “check mark” on the back. On page 92 under the 428 section they show a block with the "A". A block with an “X” is high nickle and “CX” is an industrial 428. They also mention a myriad of machining variations, but use your eyes to visually recognize the features. The folks they reference as experts and contributors are the brothers Jeff Sneathen of SEMO Classic Mustangs and Bill Sneathan of Sneathan Enterprises in Cape Girardeau, Missouri.

They did not mention a XX, however a phone call may get you an answer.
No phone numbers were mentioned.

[alhs06]

Learjockey1,
Your a saint, best lead I've got, puts some wind in the sails again.
Thanks mate I'll definately follow up.