59A Block ID centre water passages.

[JSeery]

Regardless of the size or shape of the openings in the block flow will be limited by the hole size in the heads, and of course then the head gasket. Block casting holes are often determined by core removal requirements during the casting process.

[macdonge]

Quite right JSeery... and I don't doubt as well that the passages out of the block were originally left 'generous' in order to give some latitude for flow adjustments in the evolution of head designs.

[Phil Gillespie]

Originally Posted by macdonge

Phil: I found a few references worth considering in regards to the selection of head gaskets.
1. The Ford “Repair Manual, Ford & Mercury V8 Engines” (for ‘37 - ‘48 engines) shows photos on (p. 36) of an old and new design gasket. The old design shows the 3 large trapezoidal centre coolant passages. The new design has the same trapezoidal upper passage, a large round middle hole and a small round lower hole.
2. Joe Abbin’s book “Ford & Mercury Flathead V-8 Identification & Rebuilders Guide” indicates (on p. 7-12) that “The gasket coolant passage designs evolved even if the block and head designs did not, since it was easier and cheaper to change the gasket and just as effective in some cases. Therefore it is advisable to use the latest available gasket designs for each generation rather than NOS where there is a difference.”
3. If you want the closest ‘match’ to your blocks passages, Edelbrock’s 7394 (e.g. Speedway part # 3257394) or Mac’s Part # 91A-6501-C/S/M may do the trick.
4. In my opinion however (particularly in light of references 1 & 2 above), the cylinder heads’ coolant passage configuration is probably the primary consideration in choosing a gasket set. For example, I’ve chosen BestGasket 511C’s to suit the round passages on my Offy heads.

Hope this helps.

Glen M.

That certainly helps for sure. Many thanks for the info you have provided to assist. Now know "keystone block". This is the benefit of this form there is always someone who has the answers. This will assist me for sure.
Phil NZ

[Phil Gillespie]

Originally Posted by flatjack9

Yes, I always use the later gaskets on my builds.

The CW flow through the heads being controlled by the later style gaskets is cetainly reason enough to go with the later gaskets.
These are the ones fitted at engines recent rebuild so will continue with them.
Much appreciated.
Phil NZ

[Gary troxel]

What is the Pencil test ? Thanks, Gary Troxel

[JSeery]

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Originally Posted by Gary troxel

What is the Pencil test ? Thanks, Gary Troxel

Has to do with the design of the front of the flathead block, whether it has a ledge at the top edge of the front timing gear cover or not.

"All prewar, 1932 through 1942, V8 blocks will pass what is known as the pencil test. The front of the block above the timing cover has a little shelf that makes the top of the timing cover face in the block. If you can rest a pencil on the block at this location, you have a prewar block. Make sure you are not resting the pencil on the timing cover itself."