Ted has given a good overview of the challenge of identifying a 312 engine.  Realize that 312s were an optional V-8 offering in Ford passenger cars in '56 and '57, used in the majority of '56 and '57 T-Birds (auto trans and 3 speed overdrive originally equipped 'Birds), the standard equipment engine in '56 and '57 Mercs. and the base V-8 option in '58-'60 Mercs.  No FoMoCo trucks were ever produced with 312 engines.

There's nothing wrong with a 292 engine.  For some applications, 292 have structural advantages over 312 engine blocks.  I.M.O.the advantage of y-blocks over other engine series is their propensity for producing significant torque curves for their original displacement sizes.   

To add to what he's said about engine block casting numbers here is some info. from John Mummert's web site, http://www.ford-y-block.com in the Technical section...

NOTE: 6015 is Ford's number for an engine block. All blocks have this number.

The Y-block FoMoCo engine block identification number is generally on the side of block above the oil filter for blocks cast at Cleveland.  Dearborn cast block I.D. number is near the ignition distributor and above the generator. Most Dearborn blocks were used in trucks. No Dearborn blocks were produced after 1957.

292 and 312 Blocks were machined from the same castings with the same markings. If the engine block has EBU main bearing caps it is a 292, if it has ECZ main caps it is a 312.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

312! ECZ 6015A

Betsy.  Welcome to the site.  And congratulations on your recent Y engine purchase.  As some of the others have alluded to, there are now more Thunderbird engines in existence than was originally produced.  In identifying your particular engine externally without a tear down, I’ve only found one identifier that is a positive for your engine being a 312 and that is the 5/16” dot on the flywheel flange of the crankshaft.  Not having that identifier though can still have this engine having a 312 crankshaft as there were 312 cranks produced without any identifiers on the crankshaft flange.

Block casting numbers are not positive identifiers as I’ve seen 292’s with the 312 block numbers and 312’s with 292 casting numbers which leaves positive identification in doubt until the engine is torn down.  With the heads off of the engine, then a bore and stroke check can put you closer to positively identifying your engine but even this can be misleading depending upon what was done in previous rebuilds.

With the oil pan off, then looking at the main caps can also help to positively identify the block as either a 312 or a non 312 block.  If the caps have ‘ECZ’ on them, then you are looking at a 312 block.  If the caps have ‘EBU’ on them, then you are looking at any of the other Y-Blocks that were built including the 272 and 292 combinations.  There are the rare cases where an EBU main capped block was bored by a rebuilder or racer to fit the 312 crankshaft main size but those are indeed rare.  It’s much easier to grind the 312 mains down and fit the crankshaft to a 292 block than going the other way around which involves reboring the 292 main bore to the 312 size.

Lorena, Texas (South of Waco)

That's just a typical 50+ year old used Y-Block.  The mounts do look like truck mounts.  The thermostat housing is for a car.  There's no telling what it is until you dig deeper.



Lawrenceville, GA

Also, the guy I bought it from said it came out of a truck but did come out of a t-bird tho, i gotta do some checking

Well damn if thats the case prob a 292? Gonna look for the casting number to check and see.

I see a wide motor mount up front from a 60's truck. The crossover single exhaust is probably from a truck also. I'd guess it's not a 312.

  Dennis in Lititz PA

Does not have t bird thermostat housing,dip stick in wrong location,exhaust manifolds not correct,wrong harmonic balancer, just noticed at first glance  Carl

Brought this home last night. Bought from a friend and it came out of a 57' T Bird. (So he says) I am learning about Y-blocks, possibility the info could be wrong. Friend I bought it from has more parts I have to pick up that came with it, like 600 Edelbrock Carb, alternator and linkage and blah, blah... I had to hug it as soon as I got home!