The Chrysler Collector
March / April 2010
OUR MOTORING HERITAGE Mopar Flat Head Sixes Chris Howes noticed this Antique Automobile Club of America forum article from January 2010 about side valve 6 cylinder engines. T h e a r t i c l e w a s h t t p: / / forums.aaca.org/f143/d11-vsd15-engine-274657.html An extract from this article is as follows:
FROM RUSTY O’TOOLE Up until 1938 Canadian made Chrysler products used engines imported from the US. Starting in 1938, the Canadian Chrysler plant got its own engine facility. This plant made only one engine, the flathead 6 cylinder used in US made Chryslers and De Sotos. In order to make engines suitable for all kinds of cars and trucks, they made the same block with 2 different cylinder bores, 3 3/8 and 3 7/16. Generally speaking the smaller bore engine went in Plymouth Dodge and Dodge trucks while the larger bore engine went in Chrysler and De Soto cars. By using a longer stroke crankshaft they could make the same engine in various sizes. If you compare the US made engines to the Canadian made ones, you will find they had practically the same displacement and horsepower model for model. For example the 217 cu in (US) and 218 cu in (Canadian) were a very popular size for Plymouths. Then there was a 228 (Canadian) and 230 (US) used by Dodge and later year Plymouths. This disguised the fact that the American made Plymouth and Dodge had a completely different engine.
Most of the cars exported to British Commonwealth countries came from Canada because there was no import duties between Commonwealth countries. So you are likely to find a lot of these odd Canadian engines. The easy way to tell them apart is by the length, Canadian engines and US made Chrysler and De Soto engines measure 25 1/4 inches long at the head, while the US Plymouth and Dodge measure 23 inches. Other than that they look remarkably similar. Here are some common sizes gleaned from old service data books. Right now the info I have on hand only covers back to 1942. Before that I only have the US models. There may have been some other models made in the 1938 to 41 period for Canadian Plymouth and Dodge. 3 3/8 X 4 1/16 = 218 used in Plymouth 1940-59 small Dodge 40-59 3 3/8 X 4 1/4 = 228 used in De Soto 37-41 large Dodge 40-59 some 54-59 Plymouths with automatic transmission 3 3/8X 4 1/2 = 241 used in Chrysler 38-41 3 7/16 X 4 1/4 = 237 used in De Soto 42-50 3 7/16 X 4 1/2 = 251 used in Chrysler 42-51 De Soto 51 also used in some Dodge trucks in the fifties and in military 3/4 ton Dodge 4 wheel drive Power Wagons from the forties to 1972. 3 7/16 X 4 3/4 = 265 used in Chrysler 52-54 De Soto 52-54 some Dodge 1 ton and larger trucks up to 1962 and Chrysler industrial and marine to 1972. This was the biggest and best version with full flow oil filter. - 16 -
1959 was the last year for the flathead 6 in cars and pickup trucks, after that they got the OHV slant six. The 251 and 265 were used in heavy trucks until 1962. Military Power Wagons used the 251 until 1968. Industrial and marine engines were made until 1972. A lot of these were used by Massey in combines. So don't overlook abandon ed far m machinery as a source of engines. If you compare the Canadian cars to the American made equivalents the relationship will become clear. You can see they only had 1 engine with 2 cylinder bores and 4 crankshafts. By juggling these in different combinations they made a variety of engines for different applications. I have even seen an industrial engine with 3 7/16 bore and 4 1/16 stroke for 225 cubic inches. All these crankshafts will interchange in all blocks. The pistons are the same bore for bore, but you have to use the connecting rods that match the crankshaft as they are different lengths.
FROM BILL WATSON (Vancouver, BC) For a complete list of Chrysler of Canada flatheads, 25" block, used in cars: 3-3/8" bore 201.3 - 3-3/4" bore - 1938-39 Plymouth and small Dodge 218.1 - 4-1/16" bore - 1938-41 big Dodge and 1940 - mid 1953 Plymouth and small Dodge 228.1 - 4-1/4" bore - 1938-41 De Soto, 1942-52 big Dodge and mid 1953-1954 Plymouth and small Dodge