I've got a 351 with a casting number that starts with 77 and not D7. In the lifter valley it seriously has Hecho en Mexico cast into it. Is this a good block to start with?

 

Are you sure it's not a 302? I'm not an expert on Mexican engines, but I've only heard of the 302 Hecho en Mexico engines.
The desireable feature of the Mexican 302 is its bigger main bearing caps, similar to those on a HiPo 289.
Perhaps this Mexican 351W has extra large main bearing caps as well, although the standard 351W main bearing caps are plenty robust already.

The general wisdom is that all 351W blocks are good and strong. There's some discussion about the first few years' production being strongest, but for pretty well all mild performance use there's no bad 351W blocks.

Does your engine have the threaded boss for a clutch equalizer bar machined into the left rear of the block (it's a 1/2" NC threaded hole in a boss)?

One reason this would not be a good block to use would be if it has been salt water cooled.

 

Hey Beanscoot. Yes it's a 351 for sure. It does have the threaded boss. I do have a HiPo 289 though! Early 5 bolt, std bore.

 

Like beanscoot said I have not heard of the mexican 351 however the mexican 302 is a great block to start a buildup with due to the wider main bearings. It was told for a while that the mexican block had a high nickel content in the metal but that has been disproved by several tests. If you are planning to do a high performance build the mexican block would be good and even if it is a 302 it will be able to withstand a stroker kit with ease as long as you use good valve springs to match and will be something like a 361 with a standard bore.(dont quote me on that number as it has been a while since I did the math on a stroker kit) Just measure the stroke and see if it is a 302 or 351. I would however be weary of the possible salt water in the block though. After you knock out the freeze plugs look to see how much damage is in the water sleeves.

 

It wasn't too bad in there. It's a 351 though. I've got an old Performer 351w manifold mocked up on it. I'm not going for anything big, just a mild cam and a four barrel with headers. It's going in a pretty light 64 Falcon Conv with a Toploader and a 9" from a 65 HiPo Mustang.

 

Sounds excellent. I suppose Mustang headers are available and will fit the Falcon? As I recall, putting a small block in this chassis (actually it was a Comet, and a 260 small block) required a specific left exhaust manifold which dumped under the engine to clear the steering shaft. Probably wouldn't work with a Windsor.
The clutch linkage boss was phased out in the late 70s, happily your engine has it.

What intake manifold was on that engine originally? This is one of the marine/industrial 4V intakes. It is functionally identical to the 1969-70 car 4V intake, except that it has 4 intake manifold holes not drilled to suit later engines.

 

I threw the original one in the dumpster at work. I've got a set of "Red's Headers" that are Tri-Y and made for the Falcon. They work great but I don't think they will work with the wider and taller 351. I bought a used set of tubular automotive full length headers that are made for the 63-65's that should work.

Work on me! No! Work on me!

 

"I threw the original one in the dumpster at work."

I hope it wasn't an original 4V... those are pretty hard to find for Fords!

Nice Falcon!