Vintage Oldsmobiles Curved Dash, Limited Touring, Models 40, 53, 66; Series 60, 70, 90

56 heads

Old August 22nd, 2016, 07:44 AM
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56 heads

will 56 heads and intake fit on 55 block?
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Old August 22nd, 2016, 07:59 AM
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Found this on Google search...

Intake Manifolds 1949 - 1964


Identification
The early Olds V-8s used a "raised" intake manifold design with a separate valley cover. There was also a small "bug" shield in front of the intake. The later V-8 intake seals directly to the block.
Details

Intake manifolds are cast iron unless otherwise noted.
Casting number and ID are located on top front of manifold, usually on the runners.
ID/ Casting Code Number Year(s) Application/Notes 563966 '55 or '56 4bbl. Iron. 567930 2bbl. Iron. 571145 '57,'58 371, Tri-carb, 3 2bbl. Easy to spot by the 3 carb holes. Mechanical linkage. 573388 '5? 573323 '60 394. 4bbl. Iron. D2 580676 '61 394. 2bbl. Iron D3 382856 '64 394, UHC 394. 4bbl. Iron. 382855 4bbl. Iron. 1954 and 1955 324s' have smaller intake ports and valves than the 1956 engines. 1955 and earlier four barrel intake manifolds won't fit a 1956 engine unless you put a dent in the lifter valley cover. 1957 and later cylinder heads will physically bolt on to 1949 to 1956 engines, but the port matchup on intake maniflolds will be off because different cylinder deck heights are used. 1957 and later cylinder heads have larger coumbustion chambers and valves.
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Old October 2nd, 2017, 07:16 AM
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Ok, thanks for the info. I'm still not clear, I have a 1955 324. can I install 1956 heads and intake on this engine? would it be a good idea, or should I stick with the 55 heads?
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Old October 2nd, 2017, 03:23 PM
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Yes you can .... But as mentioned above you will have to put a dent where the intake hits the valley cover. Mark the spot, heat it up and give it a thump with a hammer, it doesn't take that much.

Your compression will come up from 8 1/2 to 10 and you will probably pick up about a extra 10 to 12 hp with out a cam change.... Tedd
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Old October 3rd, 2017, 09:26 PM
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As mentioned, it should work. There were subtle changes in the '56 to achieve the H.P. gain. The diameter of the exhaust valve went from 1-7/16" in '55 to 1-9/16" in '56. The diameter of the intake remained at 1-3/4". Compression went from 8.5:1 to 9.25:1. There were also small changes in the cam and carburetor. As Tedd said, you will realize a portion of the increase by only changing the heads. Be sure they are '56 (#10). The '55 are #8 if I'm remembering correctly. In '57 they changed the block's deck height.
This change "might" slightly increase the engine's fuel octane requirements.

Last edited by Ozzie; October 3rd, 2017 at 09:32 PM. Reason: Added information
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