[steve25]

I had another Bell go off last night so I pulled out Pete's 2 books, and here what I come up with.

In his first book it list for 1967 a 360 hp and 376 hp 428, the 360 hp motor having a 10.5 comp and the 376 hp motor as being 10.75.

Well this brings up the question of if the
670 heads are all 72 to 73 CCs, then how did the compression change come about?

If you look in this same book at the detail listings on the 68 428 motors you will find that the 375 hp 428 used a .050" head gasket and the 390 hp motor used a .042" head gasket, and I believe the X stamping on the head is used to differentiate a assembled motor with the highest compression ratio as when put into inventory the factory needed a way to know how the motor was built.


I think the factory did the same gasket thing in 67 , but the book does not list such.

Now here's why I believe such!

In Pete's second book in the section on the early SD motor you will find on page 169 some shots of a 61 to 62 177 head.

In Pete's discription of the clearly marked stampings on the head he notes that the head was for a 10.75 motor with HD valve springs.

The X he states denoted the 10.75 comp and O stamping denotes the HD valve springs.

If we assume that 5 years down the road in 67 that the engineers and or the factory used the same stamping code then we now know what the X and O stamping means and then like I posted the Z stamping indicates standard valve springs for that year, or Heads that are not fully set up for air injection, I think the latter!

My 670 heads came off a GP here in the east, so no air injection.

What do you folks think?