58 vs 59/60 Tri-carb expert needed

[Paul]

Looking for a resolution to a question I have been wrestling with. I’m interested in buying a tri-power for my 59. A gentleman offered to sell me a 58 version. He is convinced it is interchangeable with 59/60 engine. My understanding is that when Cadillac increased the 58’s 365 engine to 59’s 390, the engine grew taller to accommodate the 4.00 stroke. The 58 stroke was somewhere around 3.63, give or take. The result was also that the heads went farther apart. Therefore, the 58 intake manifold is too narrow and cannot be interchanged. The 58 tripower is a one year item. Am I mistaken? Any clarification â€"and resolutionâ€"would be appreciated!

[76eldo]

I don't know for sure but I have never heard of these interchanging.  I would not recommend trying it.

Brian

[Rockfish39]

Paul,
        The gentleman that was trying to convince you about the interchangeability of these intakes (drumroll please) WAS ABSOLUTELY RIGHT!!!

331s, 365s, and Gen-1 390's all have the same deck height. The heads are no further apart, the intakes are not wider.

Between the 365 and the Gen-1 390, the 390's added stroke DID NOT come at the expense of needing a taller deck block. Cadillac used shorter connecting rods instead with that 4.00 in bore piston. 365 rod is 6.625" long. Gen-1 390 rod is 6.5" That 1/8" is taken up by the longer stroke of the 390 crank, which also is not 4". It's
3.875"

a '58 3*2 intake will fit any of these engines. No problem

BUT be advised, The '59-60 tri powers take a larger 2GC carb  on the mounting pads than the '58 does, which is what makes the '58 intake unique. More displacement means more CFMs needed at any RPM was the reason why.

Pay particular attention to this when making your carb selections on any 3*2 intake that you buy.

Rock