In a junkyard I found a 68 Firebird 350 2bbl with a 3 speed manual trans. Complete car. The RH exhaust manafold has no heat riser valve. Never had one at all. The date matches the block and heads and the engine is original to the car. Did manual trans cars not have this heat riser valve? The engine also has a block heater and it really doean't get that cold here so perhaps the car came from Canada and was built for Canada?? Any ideas? I'm putting together a clone 68 350 HO 4-speed and I bought the manafold just in case. Thanks