So.. I'm in the Chassis Service Manual reviewing the crankcase ventilation diagrams. What is the 'SM' in 455 cu in A Body SM?

 

https://classicoldsmobile.com/forums...estion-168736/

It applies to a car with a Manual Transmission.

 

Very well. Thanks very much.

 

That's because big block cars with manual trans got the same dual ventilation PCV system as did the W30 cars. The PCV valve goes to a barb on the intake manifold behind the t-stat and both valve covers have breathers that connect to the air cleaner. Note that the cast iron BBO intakes for 1970-72 have a boss cast behind the t-stat. For MT (aka SM) applications, that boss was drilled and a hose barb was pressed in for the PCV. The basic casting number is the same in both cases, which has led to a lot of confusion on the part of people who think that they have a "rare" cast iron MT intake, but it doesn't have the hose barb.

 

Thanks, Joe.

I had seen a similar post where you explained this (slightly different set of pics), but I didn't know that SMT, MT, and SM were all interchangeable. I recently purchased a car not running and driving... with some disassembly as well (and parts missing). Trying to put it all back together correctly; glad to have the experts keep me focused on the correct diagrams.

JW