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aeronca65t
Great Pumpkin
Offline
Re: intake manifold cooling
The small water jacket in the intake manifold of 1500 Midgets is designed to speed-up the heating of the manifold. Once the car reaches operating temps (coolant at about 193 F), this water jacket is likely to have little effect except at very cold outside temps (where it might help fuel atomization).
The history of the device is likely linked to the primitive carbutetted emissions systems used on these mid 70s cars....getting the manifold up to temps makes for smoother running of this very-lean setup. A water-heated intake manifold also improves cold-start mileage (the U.S. EPA method).....another important benefit to the manufacturer.
My 1500 race-engine uses a standard manifold (but not standard carb). The manifold coolant hoses are not connected and the intake manifold runs stone-cold (due to the cooling affect of the intake charge, I guess). I'm not running a catalytic convertor and my header is wrapped, so this also may help. Another car (non-LBC) that I have has a water-heated manifold: you can feel the hoses connecting to the manifold heat up before the rest of the engine (I tried this).
As mentioned above, the water-heated manifold is a popular idea that has been used on many cars (even many pre-emission cars) to improve cold-running of the engine. Coolant flows through this water-jacket as soon as the engine starts (partly due to thermo-syphoning and partly due to the surging effect of the water pump). Once the thermostat opens, the flow is increased. The coolant pickup hose and control valve for the heater core is located near the back part of this water-jacket, but it would not control any flow though this water jacket.
By the way, I pick up cold air for my carb via a good-size hole punched in the right-side fender well. Since the car is also street driven once-in-a-while, I have added a baffle to keep out dirt and water....this was much easier than running a long, large-diameter hose and plenum in front of the radiator to pick up cold air.
The small water jacket in the intake manifold of 1500 Midgets is designed to speed-up the heating of the manifold. Once the car reaches operating temps (coolant at about 193 F), this water jacket is likely to have little effect except at very cold outside temps (where it might help fuel atomization).
The history of the device is likely linked to the primitive carbutetted emissions systems used on these mid 70s cars....getting the manifold up to temps makes for smoother running of this very-lean setup. A water-heated intake manifold also improves cold-start mileage (the U.S. EPA method).....another important benefit to the manufacturer.
My 1500 race-engine uses a standard manifold (but not standard carb). The manifold coolant hoses are not connected and the intake manifold runs stone-cold (due to the cooling affect of the intake charge, I guess). I'm not running a catalytic convertor and my header is wrapped, so this also may help. Another car (non-LBC) that I have has a water-heated manifold: you can feel the hoses connecting to the manifold heat up before the rest of the engine (I tried this).
As mentioned above, the water-heated manifold is a popular idea that has been used on many cars (even many pre-emission cars) to improve cold-running of the engine. Coolant flows through this water-jacket as soon as the engine starts (partly due to thermo-syphoning and partly due to the surging effect of the water pump). Once the thermostat opens, the flow is increased. The coolant pickup hose and control valve for the heater core is located near the back part of this water-jacket, but it would not control any flow though this water jacket.
By the way, I pick up cold air for my carb via a good-size hole punched in the right-side fender well. Since the car is also street driven once-in-a-while, I have added a baffle to keep out dirt and water....this was much easier than running a long, large-diameter hose and plenum in front of the radiator to pick up cold air.