This car is for sale and claims it is a 312 engine, but several things make me question that.  The heads have sand core plugs/freeze plugs in the ends, an aftermarket intake manifold and carburetor, and headers.  I was under the impression the freeze plugs were pre-56, which would preclude this being a true 312.  Is that correct?  I went to Mummert's site and I  have printed off the block numbers, head numbers, crank identifying dot, etc., but if this is bogus, then the price is way too much for this car.  Any ideas would be appreciated.  Thanks, Joe-JDC

JDC

Joe.  You might want to check the casting numbers on the heads.  ECZ-C heads were supplied with and without the end core plugs in 1956.  I’ve even come across an unmolested 1956 engine that had one of each.  As a general rule all 1955 heads had core plugs in their ends but the change to non-core plug heads occurred during the 1956 model year run.  It’s still possible to have a 312 bottom end with the top end being off of a different Y.
 
As far as identifying the short-block as a 312, the casting numbers on the block will help but those numbers are not definitive as some of the 292’s shared the same casting numbers as the 312’s.  The 5/16” dot on the flywheel flange is very good indicator of the crankshaft being a 312 but be aware that there are 312’s out there that have no dot on the flywheel flange.  And then there are the 312 cranks that are in 292 blocks with just a minor amount of machine work.  Even checking the bore size is not definitive as any 292 bored to 3.800” or more can be confused with a 312 bore size.  The ‘ECZ’ on the main caps is the best identifier for the block itself being a 312.

Lorena, Texas (South of Waco)