Hey Y'all, the engine on my 1969 RS/SS Pace car seems to have an option called "Pre-Heat". It's a tube that runs from the Air-cleaner snout back down into the manifold to feed it heated air. http://www.camaros.org/emissions.shtmlThe Controlled Combustion System (CCS) was introduced in 1968 and was used on cars that did not receive the AIR system (automatic transmissions). CCS improved combustion efficiency via recalibrated carburetor and distributor settings and higher operating temperatures (compared to 1967). The higher operating temperatures were accomplished by using a 195°F coolant thermostat (instead of 180°F) and the use of a thermostatically controlled air cleaner (ThermAC). The ThermAC system was designed to warm intake air to 100°F when underhood temperatures were less than 100°F. It consisted of a damper door mounted on the snorkel of the air cleaner which directed warm air from a heat stove on the exhaust manifold into the air cleaner. http://www.camaros.org/forum/index.php?topic=1032.msg5591#msg5591
Exhaust Manifold Part Numbers for 1969 Camaro 327/210 hp, 307/200 hp, or 350/250, 255, 300 hp engines w/auto transmission and no A.I.R.
LH side p/n: 3942529
RH side p/n: 3932376
These manifolds were also used in 1969 on Chevelle and Chevy II 307 and 350 engines with auto tranny and no A.I.R.
Exhaust Manifold Part Numbers for 1969 Camaro for all manual transmission, with A.I.R., small block Camaro applications for 1969 including the 302 Z28 engine. These manifolds have drilled and tapped connections for A.I.R.
In 1969 Camaro SB applications, there is a distinct difference in the RH manifolds between a standard transmission ("826" manifold) and an auto transmission ("376" manifold). The "376" manifold incorporates a heat stove, is wider, with the heat stove riveted to it. (The "826" manifold for standard transmission cars does not have the heat stove, since the Thermac / heat stove was an emmission system only applicable to an auto tran setup.)
I saw on one of these heat stove tubes last Sat. at a local junk yard - it was on an early '70's Chevy pick up truck. Appeared to be identical to the one shown in the pic. Thought about buying it, but didn't.