I'm having difficulty determining what size engine is in my 1951 GMC half ton. The trouble I'm having is that the engine serial number does not look conventional. My research indicates the first 3 digits should indicate the C.I. of the engine. However my serial number stamped just above and to the rear of the dipstick is C489609. The truck was made in Canada and its a 9314. As you can see in the attached pictures the ID plate indicates that it is the original engine.
Your GMC was made in Canada. It was factory equipped with a Chevrolet 216 engine. The "first 3 digits is the engine size" is only true of USA manufactured GMCs.
I've been told that it is a 235, as well as being a 228. by different people that seem to have more knowledge than myself on this matter. I'm not all that educated in this vintage of GMC's but after a little research, Canada didn't start making GMC engines until 1954 in St Catherines Ontario. So that might indicate that the engine was actually made in USA. Just a theory.
I believe the 228 is the common motor on the half tonn GMC, but the blocks are all the same for displacements 228 and larger (up to 302 ci) The casting number for the block should be 6107326 for any of them from like 1937 to 1955. You'll find the casting number as raised digits on the block on both sides of the engine. The one on the driver's side is to the right of the distributor boss. If you google the casting number followed by 'GM' it will tell you what you have The tag in your photo is probably meaningless unless the orginal block is in your truck - you need the ID stamped into the machined distributor boss to decode what you've got for an engine.
True for USA made trucks. Post WW2 Canadian made trucks until at least 1959 (newest I have documentation for) used Chevy 6 cylinder and V8 engines, with Buick V8s used in the larger trucks. The picture that 51resurrection posted is a Chevy 6. I said 216 because that is what it would have had from the factory. Early 235 engines also had valve covers like the one in the picture. 6107326 is the casting number for a GMC 228, manufactured from 1939 through 1952. The number on the machined block surface immediately to the rear of the distributor should give information that shows manufacturing plant, date and size IF Canadian Chevy engine numbers follow the same scheme as US engines.
