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Buick Engine Identification, Until 1952

Engine number location - 1935 on right side of crankcase. 1935-52 series 40, 50 on right side of engine near front. 1936-52 series 60, 70, 80, 90 on right side of engine near rear.
320 straight eight 263 straight eight
How to tell the big ones from the little ones?

You will notice on the images above, the 320 is on the left and the 263 is on the right. On the 320 the engine number boss is located towards the rear from the distributor and on the 263 the engine number boss is located towards the front from the distributor. You will also find that the 263 rocker cover is about 30 3/4" long and the 320 rocker cover is about 33 3/4" long. Unfortunately this makes it more difficult to squeeze a 320 into a 263 hole. That is why the big cars had 4 holes and extra hood length.

STARTING ENGINE NUMBERS (hyphens can be ignored)
1935 40 4-2937408 1936 40 4-2995239 1937 40 4-3166225
50 5-2922072 60 6-3001000 60 6-3176225
60 6-2922072 80 5-3001000 80 8-3176225
90 9-2922072 90 9-3001000 90 9-3176225
 
1938 40 4-3396937 1939 40 4-3572652 1940 40 4-3786214
60 6-3396937 60 6-3572652 50 5-3786214
80 8-3396937 80 8-3572652 60 6-3786214
90 9-3396937 90 9-3572652 70 7-3786214
80 8-3786214
90 9-3786214
 
1941 40A 4-4074859 1942 40A 4-4457941-A 1946 40 4558037-4
40B 4-4074859 40 4-4457941 50 4558037-5
50 5-4074859 50 5-4457941 70 4558297
60 6-4085000 60 6-4457941    
70 7-4085000 70 7-4457941    
90 9-4085000 90 9-4457941    
1947 engine numbers continued from 1946
1948 40 4999881-4 1949 40 5220972-4 1950 40 5568000-4
50 4999881-5 50 5220972-5 50(std) 5628758-5
70 4999881-7 70 5220972-7 50(dyn) 5624734-5
70 5635021-7
 
1951 40(std) 6240128-4 1952 40(std) 6646232-4      
40(dyn) 6240100-4 40(dyn) 6646230-4    
50(std) 6240564-5 50(std) 6647024-5    
50(dyn) 6240100-5 50(dyn) 6646230-5    
70 6240161-7 70 6652000-7