Thanks for offer Mike, the only thing I'm seeing non original on this car are the hub caps. That might be something we'll look for down the road.
Was back at shop yesterday and got to the engine, casting letters confirms it is the original 256ci EBY. Talked to the owner to what was wrong with the engine. He says a squeal and a knock. I've heard that noise before, spun rod bearing comes to mind. So finally some straight talk and confirmation to what it is I'm working with.

With my 54 Merc, I went the route that the guys stated here. I called many of the companies that rebuild engines & they also steered me away from rebuilding the 256.  I kept the original & is still under my workbench since 2000.    If you need any parts, let me know ,as I bought a lot back then. I have some stainless trim.      Mike

Sorry for the confusion as I'm in somewhat the same situation myself and am sorting this out so bear with me. As the car sits the engine is removed. My brother had several classics and this shop did all of his work. They told me the Merc has been sitting there in this condition for at least 20 years. Thinking about that it's very possible. He had changed his mind over the years over the engine replacement from what they told me. Modern or original. Why nothing was done only he knows and I have know way of knowing other than some recent conversations before his passing which was a modern power plant to which I was opposed. The engine is out of the car, I have not seen it yet to verify it was a 312, I'm only going on what I was told yesterday. The fate of the car at this point is somewhat undetermined but the value would be considerably higher as a running driving car IMO. So we are sorting this out. I believe I have found a rebuilt 256 to put it back to original so that is an option. I have also found a couple 292's, runners and cores. We are going to weigh this option also. I have yet to talk to someone about rebuilding one of these and also have a local lead to follow up on for this. This will be no hotrod, just needs a sweet running dependable engine for my sister inlaw to drive if she decides to keep the car. If the heads from the 312 are the better heads to use and if these are with the car we'll use them. Will check casting numbers as I proceed. I realize if I put my nose to the ground and really wanted to find a 312 parts I probably could and the "hunt" is always fun. However that is not the goal unless it's drops into my lap. The 292 is the most common and probably the easiest to find and quickest solution. I hope I've cleared up some confusion. I do appreciate all the replies!
Thank you,
Dick

Sonic testing any block is recommended when any serious overboring is contemplated.  The ’54 Ford and Mercury engines had a larger cam bore which complicates using 1955 and up camshafts.  For that single reason, it’s recommended to simply use a ’55 and newer block as your replacement.  292's are the obvious choice but don't discount using a 272.  The 1954 water pump and fuel pump can be retained if desired for originality purposes on the newer engines as those are connected to the 1954 specific timing cover which will bolt directly to the later model blocks.
 
It would be nice to have some more detail on what’s actually in the car now.  A ½” waterpump bypass hose and 5/6-18 bolts holding the fuel pump to the timing cover will at least tell you that the original 256 timing cover was used but does not guarantee that the engine itself is a 256.  Many people don’t recognize the differences in the water pumps but the 256 had a physically smaller sized water pump than the 1955 and later engines.  As has been mentioned, once the pan has been removed, then main cap identification will help to determine if a 312 block is sitting within the frame rails.  While many 312 have a 5/16" raised dot on the rear crankshaft flange, not all of them have this and these are mistaken for being non-312 cranks.  A cylinder wall bore check may also help to identify which engine it is but with overboring these engines being rampant during the day, there are no guarantees in positive block identification in doing this.  The block casting numbers along with the casting date can go a long way in identifying what engine you have so those would be nice to have.

Lorena, Texas (South of Waco)

Ok, I guess I'm not the only one confused. The car would have been a 256, OEM. Now it has a 312 with a broken crank. So you're looking for a 292 to replace it. Is that right?

If not, fill us in on how far they've torn the engine down, and just what they found. A couple pictures of the end of the crank, or the main caps would help. I'm just south of Seattle, and I've got some spare parts.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

There an old saying  which I will paraphrase

To a seller, every YBlock is a 312 until you look inside


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

The crank is harder to come by but still not that hard to find if you take the time to look.  If that is all that is broken, then it shouldn't be a big deal.

Main bearings might be difficult, depending on the size needed.  Otherwise, typical rebuild stuff should be pretty easy.


Lawrenceville, GA

I was assuming it was the original engine by the condition of the car.  Aren't 312's and parts harder to find?

This doesn't add up.  First, it is a 256 that they can't find parts for.  Now it is a 312 that broke the crank.  Unless there is some important piece of info that we outsiders are not aware of, I'd seriously evaluate the trustworthiness of that shop.


Lawrenceville, GA

Looks like a 292 it is. Just got back from looking at the car, they tell me it's been there for 20 yrs! The engine that was in it was a 312 and it broke the crank.

Dick