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Discussion Starter #1
How can I tell if I have a mexican block in my mustang?
 

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Probably some other markings, but the blocks I've seen will have "Mexico" cast in the lifter valley under the intake.
 

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Discussion Starter #4
So there is no 289's that are Mexican blocks? Figures, lol
 

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So there is no 289's that are Mexican blocks? Figures, lol
It might be worth looking into regardless, your 289 might have a 302 block. Happened with my friend's '66, he found out he had a 302 block with 289 heads.
 

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I thought the high nickel HiPo blocks were mecho en mexico?
 

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Mexican block 302's had the heavier main bearing caps like the HiPo's, but no HiPo blocks came from Mexico. They were standard casting blocks that were hardness tested as they came down the assembly line. Mexican blocks, on the other hand, are rumoured to be beefier than standard blocks, but the beef is not really anywhere that benefits the strength of the block. My machinist says that the Mexican block cast iron is actually "softer" than standard in most cases, as is evidenced by the lack of wear on his bore cutters and honing stones when working the Mexican blocks. Just sayin'
Best,
Al
 

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Agreed. The HiPo-looking bearing caps are the main point of excitement about the Mexican blocks but basically they were just Ford blocks made in Mexico. Even though the bearing caps looked the same, they had different numbers than the real ones from a HiPo and they weren't produced until after the HiPo was gone.
 

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Actually there were some Mexican 289s. I have one. The casting number is Z5AB-6015-A. Which I assume means it was first cast in 1965. Probably like the American 289s, it was used till 67 or early 68. I am just guessing at that part though. So far, I have found zero info on these blocks. I have been messing with small block Fords since 1986, never heard of one or anything about such a engine. I have found pictures of and read a little about Mexican 351W blocks, but no Mexican 289s. The guy I bought this engine from said it belonged to a buddy of his, who lived in Mexico. He went down to Mexico and picked up the block and crank and brought it to Texas, where I found it and bought it.

Some of the things I have noticed with the block are, the two bosses that are on the front of either side of a Mexican 302, that are not used. On this block the front of those two bosses, have been machined flat, then both bosses are drilled and are tapped for threads. So prior to 1968, those bosses on the Mexican blocks were used for something. I read something on Wikipedia saying the bosses were at one point, used for brackets, when they were used in trucks, in Mexico. But even Wikipedia, does not talk about the Mexican 289s. It says the Mexican 302s started in 1968, in the Shelby GT 350s. Then claims the blocks were made and used up into the 1990s, in cars and trucks. But that is BS, I know for a fact. Now, they were used in industrial applications up into the 1980s and I think 1990s. I have a buddy who was working on tow tractors, back in the early 1990s, those military tow tractors had Mexican 302s in them. The latest I know of Mexican 302s being used in American cars and trucks was the late 1970s. In the 1980s, Ford went to thin wall castings, to reduce weight, to improve fuel mileage, so there were not heavy, early style blocks used in US cars or trucks, in the 1990s or 1980s.

I also have a 1971 Mexican 302. The blocks look very similar, it's obvious to see how the blocks progressed from the 289s to the 302s. There were not many changes. I still think the original Mexican blocks were based off of the 289 Hi-Po molds. I have said that for years. Now having a Mexican 289, seeing how much it looks like a Hi-Po, like the Mexican 302s. I really think the Americans only took one block mold to Mexico, that they copied, then slightly modified. And that one mold they took to Mexico was a Hi-Po. But that's been my theory for many years.

Another closer picture of the valley.

In this picture you can see the block has the threaded hole for a Z bar, for the clutch linkage.

This picture, you can see the thick main caps.

Close up of the main caps.

The casting number followed by 289 and then what I assume is a date code, below the casting number.

The front of the block, where you can see the machined, the two bosses, then drilled and tapped them.

For comparison, my Mexican 302.

The casting number, looks much more like a US casting number, than the Mexican 289 casting number.

Picture of the top of the block.

Bottom of the block and the main caps. Now, something else to point out, is both the Mexican 302 and the Mexican 289, have a threaded bolt hole, on the right side of the number 3 main web. I would assume that is to hold a pick up tube, for a rear sump block. But not sure. I have seen that on Mexican 302s, many times. The Mexican 289 I have, also has it.

Then the front of the Mexican 302, where you can see the two bosses on the outer front corners of the block. They are left as cast. The front sides have not been machined flat, like the Mexican 289, much less also drilled and tapped, like the Mexican 289 I have.

Something I have wonders about, on the Mexican 289. I would assume that's what they put in the early Mexican Shelbys. I am pretty sure they made Shelbys in Mexico as early as 1967, but possibly earlier. I would bet all of the Mexican Shelbys have Mexican cast blocks and heads. The only Mexican Shelbys I have ever found much of any info, on, and it's very little, is the 69 Mexican Shelbys. I know they had 351Ws in, them I wonder if that's where some of the Mexican 351W engines came from. Likely all Fords produced in Mexico, had Mexican made engines in them. For some reason, they just don't seem to come across the border, like the people of Mexico do. I do know that all of the Mexican Shelbys were Gt 350s, they did not do any GT 500s in Mexico.
 

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The Z5 block was the first generation block made in Mexico . Yours was cast on March 20 1968. The extra bosses on the front of the block were added to accommodate different front bracketry used in Mexico. The block was changed in the front to the C8AM design in very late '68. NONE of these were "high nickle" . The rumor evolved from "different alloy" ( as your machinist noted) which we found in the late '70s. Ford did use the C8AM blocks for "service" 289 HiPo short blocks starting in late '68. Several friends ordered and received a Mexican block , hipo crank , Boss 302 rods and cast flat top pistons all assembled at the Cleveland engine plant as a "HiPo" over the counter short block. The four barrel intakes were different as well . They had the "normal" 1" tall aluminum spacer incorporated into the iron manifold. This had people calling the "high rise iron" manifolds but they had no power benefit.
There are 351 Mexican blocks as well. They are not high nickle either.
 
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