Intake manifold differences

Evinrude Boater

Evinrude Boater

Lieutenant Junior Grade
Joined
Jul 6, 2004
Messages
1,148
I'm changing the engine block on my 1964 Speedifour and using a the engine block from a 1963 Starflite. I noticed the intake manifold on the 64 Speedifour has two channels in the surface where the carb mounts; the 63 Starflite manifold is completely flat. The carbs are the same and the gasket covers these channels. What are the channels for? Is this an improvement for 1964?
 

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F

F_R

Supreme Mariner
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Jul 7, 2006
Messages
28,226
Re: Intake manifold differences

The '64 has a hot-air heated automatic choke. Those channels are to provide an airflow to the choke. A different carburetor completes the picture.
 
Evinrude Boater

Evinrude Boater

Lieutenant Junior Grade
Joined
Jul 6, 2004
Messages
1,148
Re: Intake manifold differences

FR, you're right the 64 is hot air choke and the 63 is hot water choke but doesn't the hot air come from the tube connected to the exhaust cover? I can't see how any hot air flows in these channels. I don't use the automatic choke so it probably doesn't matter anyway.
 
Joe Reeves

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Intake manifold differences

Hot air from exhaust baffle plate area does not flow by itself. It is drawn into the choke activation area via the two intake manifold downdraft channels.
 
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