Head Identification

[Tony Press]

Re posting this as I'm still wondering.....



I dug out my spare head and looked at the production date? - 30.7.5 part number 1A 684

Would the compression ratio of this head be any higher than that of the earlier 1929 head with the brass plugs where the priming taps used to be?

Cheers,
Stephen

I think this is the progression-


The earlier low compression head with tap primer plug holes was 1A 38 (Part No BC 28)

The primer holes were deleted, but other than the parts listings deleting the plugs there wasn't a change in the part number or casting number shown on the cards for this later style of 'low compression' head up to 1933.

Casting number 1A 670 was introduced under Part Number BC 82 in August 1933 with a slightly raised compression (5.2?) .


Casting number 1A 684 for BC 82 appeared sometime before 1936 (not sure of the change here but it is listed for the three bearing engine ?). 

In 1936 head number is listed as 1A911 - the new 'high compression' with two bolt water outlet.

Out of interest the later head gasket is shown as 1A 912 Klingerite or 1A 915 C/A.