Re: Question on my 1937 Twelve's Engine Number

Posted by Owen_Dyneto On 2014/5/5 9:25:21

The different CR heads are not identified by part numbers. The letters "HC" cast in letters about 5/8" high at the top of the head near the rear indicates that it's a high compression head. "LC" similarly indicates the low compression head (primarily but not exclusively used for export models). The standard heads had no markings. This information is right out of the shop manual.

When in doubt you can cc the heads to determine the CR; the standard head was 37.5-41.5 cc; 23-27 cc for the high (7.00) compression, and 44-48 cc for the low (6.03) compression.

The aluminum heads allowed better heat transfer which in turn allowed higher compression ratios; however the earlier cast iron heads were and are much sought after as replacements as the aluminum was, by today's standards, a rather primitive alloy and they have suffered from corrosion effects, etc. New aluminum heads in modern alloys are available from several sources, but be prepared for prices in the range of $2000 each or thereabouts.