1951 331 interchangeability?

[Mowerhoarder]

Does anyone know what parts interchange between the older 331's and other engines? I'd like to put a set of 365 or later 331 heads on my 51' but don't want to have to do big amounts of work and screw something up

[Lexi]

The original edition Cadillac Master Parts List volumes that I have consulted, list separate part numbers for 331 cylinder heads, when compared to those equipped on 1956 - 1958, 365 V8 Cadillac cars. While different numbers do not necessarily rule out a potential "fit", someone who has actually attempted this should chime in. Clay/Lexi

Note 1: The 1952 Cadillac MPL list separate part numbers for 1951 and 1952 cylinder heads, with a change for '52.
Note 2: The 1956 Cadillac MPL does not provide any cross over compatibility information, 331 vs 365.
Note 3: The 1957 Cadillac MPL does not provide any cross over compatibility information, 331 vs 365.
Note 4: The 1958 Cadillac MPL does not provide any cross over compatibility information, 331 vs 365.
Note 5: The 1959 Cadillac MPL does not provide any cross over compatibility information, 331 vs 365.
Note 5: The 1961 Cadillac MPL does not provide any cross over compatibility information, 331 vs 365.
Note 6: 1956 Cadillac 365 cylinder heads are a potential nightmare to deal with.

[Warren Rauch #4286]

  More bad news
 Hollander Cadillac Cylinder heads
   #433 Cadillac 49-51
   #432 Cadillac 1952 Auto Wreckers report #434 (53-54) will work with Valves and Springs
   #434 Cadillac 1953-54 by switching Temp gauge plug
      Note #432 has been used ,but 53-54 has larger oil holes
   #494 Cadillac 1955
Head gaskets group 8.2317 (60 Book)
   49-52  1457740
   53-55  1462808
   56-60  1473154

 Exhaust manifold gasket group8.4454 (1960 Book)

49-51 front /rear 1451916
      center      1451917
52-55 front/rear  1458619
      center      1451920
56-60 front/rear  1463109
      center      1463112

  Since the head gaskets are different things may not fit together proper. There is a  chance since  1949-52 head gaskets are the same. Hollander says 52-54 heads have been interchanged. So they may bolt up. Watch for coolant holes,oil drain back holes,proper seals from the gaskets on both head and block,and  can you find pushrods,rocker arms, etc. that will work?If you have the parts on hand and can match them up,they may not be that different. One way interchanges can work out.. And the exhaust gaskets are different too. Will the manifolds work?

Too much work for me. I'd try to find the proper parts.

Warren

[Mowerhoarder]

Thanks for all the info! I should mention that the car is currently just fine, I was just wondering if one of the other heads would fit for more compression/flow/horsepower but I guess I could have bigger valves put in mine and have it decked a bit and ported. I know Studebaker rocker arms are adjustable and are a direct fit for the caddy so that shouldn't be an issue if I decide to go with a cam as well.