I have been a keen reader of the site for some time and now would like some advice on the engine in my 55 Merc.  The block is a 59-60 292 or 312 according to the numbers but the heads are EBU  which are 54 239s,the car runs fine but as this is my first y block its hard to judge. I have recently purchased some ECZ-C  heads and would like to know your thoughts on changing them over thanks Pete 

The C heads would be an improvement for performance and driveability, but should be accompanied with an intake/carb upgrade, also a '57 and later distributor to take advantage of the mechanical and vacuum advance capabilities.  The '55 all vacuum advance distributor is not compatible with a non-55 carburetor.

John - "The Hoosier Hurricane"

thanks John the car already has a 57 dizzy with a new 465 holley so the heads were the next thing to sort out. Ive always had flatheads so the y block is a new deal for me Pete