Lookin for the Cadillac Guru's

Was wondering my gains and losses if I put my 55 331 bottomend and use my 57 365 heads. The 55 has a comp ratio of 9:1 and the 57 has a CR 10:1. I havn't pulled anything apart yet and wanted some input before I start screwing around. I'm hopin to get close to 300HP with this combo and 2 WCFB's and a mild cam for now.Thanks

 

Not much gain.The heads you want are the 390's and then have Chevy Valves intsalled with a set of adjustable Rocker arms.Intake manifolds from 49-62 are all the same.

 

So the Combustin chamber and valve are the same size as the 331's. I'm just trying to use what I have layin around and not get into machinin blocks and eatin up money as I'm close to gettin my car on the road.

 

No I think the 365's were a little larger actually.

 

I have been told that on a 331 the later 331 heads are the best to use, very smooth and responsive. They are better matched for the smaller displacement. The 390 heads come into their own on the larger inch engines. You are not going to need a ton of flow at high RPM, because it is a Cadillac, it won't make high RPM. Let me know if you want to get rid your 55 331 heads as I have 2 1950 engines I'd like to use them on.

 

On my 331 I punched it out to 354 and I ran 61 390 heads on it with headers..Ran like a Raped Ape! Plenty of low end and mid to upper power..But I also had a professional old timer Cam grinder make the Camshaft up as well.The 331 Heads are really too restrictive to waste your time with.56 365 heads have smaller valves than 57/58 365's.The larger ports and larger valves on a 390 really let those 331's breathe..I'm tellin ya fellas... you're gonna want those 390 heads on that engine.(spoken with a Christopher Walken voice)

 

Yeah I'm plannin down the road to put 390 heads on my 57 365 and let it breath. Like I said I'm lookin to get a little more out of my 55 with what I have layin around and not use any of my NOS stuff.

 

For what it's worth, the old speed catalogs listed three different sizes of header flanges for early Cadillac heads; '49-'51, '52-'55, and '56-'62. I've got a pair if '50 cylinder heads, and the exhaust ports are TINY.

 

The early blocks do have some small exhaust ports. I got a 51 motor that is takin up space in the back of my storage. There isn't any old Hot rodders in my area that have any Cadillac wisdom that I can take in. I've got a friend who used to build engines for Top Fuel who says he'll lend me a hand.

 

I'm a new guy rebuilding a '51 Cad engine. It is a mess with the block being about the only worthwhile piece. Even the crank had a crack that show up with magnafluxing! I was given a good crank (390) and some good pistons. I know all year heads will bolt up. The small exhaust valves were enlarged in 1952 and kept until the 390. It is interesting to study the valve lift, timing and so on on these early 331's. They changed every year! I strayed on a post here where a fellow was boring his 331 to 365...
My question deals with lifters and pushrods. The lifters changed during 1957. So you had engines using 49-57 or 57-67 lifters. Very interesting. Did the push rods change too? If so, HOW.
I am open to creative suggestions!