Advantage of Coolant thru Intake Manifold?

[SupDoc]

Is there any advantage of running coolant through the intake manifold? I'll be swapping my Canon intake and Weber throttle body over to the L20 that I'm going to install. The old L16 that they were attached to had the coolant holes in the cylinder head tapped and plugged. See following picture.

 

 

The cylinder head on the L20 still has these openings, so if I don't plug them, coolant will be running through the intake manifold. See following pic...

 

 

Plug, or not to plug? That is the question.

 

 

[datzenmike]

To flow coolant, it has to exit the intake at the front right at the base of the carburetor and join the thermostat by pass tube traveling down to the lower radiator hose where it enters the water pump to complete the circuit. You could simply plug this outlet.

 

 

 

As to any advantage?

 

Most certainly I would keep this feature. All L16/18s and L20Bs after '77 had the coolant flow intakes. The coolant warms the intake in cold and extreme cold weather helping to evaporate the fuel droplets mixed into the intake air by the carburetor. On extremely warm days the coolant absorbs radiant heat from the extremely close extremely hot exhaust manifolds. Providing a more stable intake air temperature over a wider range of weather conditions promotes better performance and economy. A third good reason to keep it is it promotes good coolant circulation in the head reducing any hot spots at the rear. After all, the hot coolant at the rear of the head would otherwise have to travel all the way to the front to get out through the thermostat. 

 

Only the U67 head on the '75-'77 L20Bs didn't have this feature. It co-joins the intake to the exhaust and uses the hot exhaust to warm the intake directly below the carburetor. It was regulated by a thermostatic spring loaded flap gate. It worked but only if maintained and with age, rust and neglect could and did seize in any position from full open, baking and over heating the intake air, to closed and causing very poor running in cold weather and a slow warm up. For the '78-'80 L20Bs the coolant circulating intakes were reinstated on the W58 heads. 

 

 

If the cannon manifold does not have the coolant passages the holes in the head will simply be sealed when the intake and gasket are installed. There is absolutely no reason to tap and plug the holes.

[banzai510(hainz)]

Haveing a Weber down draft and live in a  verycold climate yes I would run it.

I had a 510 that had a head w/o the holes and didnt know it at the time. carb was ice frozen going ove the pass and killing it.

 

If  warm  you have sidedrafts I would plug it up as you did.so it never leaks again

Edited August 7, 2023 by banzai510(hainz)

[Stoffregen Motorsports]

I used to hate that coolant going through the manifold, but then we tested it and found that it actually cooled the intake and helped with horsepower.

 

If the manifold does not have it, I would still tap and plug the head, as this eliminates a possible leak point in the gasket. It also helps with future service. If you ever have to remove the intake from a head with plugged coolant ports, you don't need to drain the coolant first.

[SupDoc]

Thanks for the the explanations. I think that I am going to flow coolant through the intake manifold, since the Cannons give you the option. It's a little counter-intuitive, since it seems like I'll be losing some cooling efficiency, since some of the coolant will now be by-passing the radiator and going directly back into the water pump inlet. But it sounds like this is common practice, so I'll just go with it.

[banzai510(hainz)]

Since you live in california(warm) and have the plugs installed I would just bolt it on there.

[datzenmike]

Well it works to remove heat too if in extreme climate. Exhaust manifold is 500F and more, just 1/2" away from intake runners. Under hood temperatures in 100F weather qualify as extreme. Coolant is a relatively 'cool' 180F

[SupDoc]

48 minutes ago, banzai510(hainz) said:

Since you live in california(warm) and have the plugs installed I would just bolt it on there.

 

The picture with the plugs, is on the engine I'm taking out. The L20 that I'm going to install doesn't have plugs.

[Stoffregen Motorsports]

3 hours ago, datzenmike said:

Well it works to remove heat too if in extreme climate. Exhaust manifold is 500F and more, just 1/2" away from intake runners. Under hood temperatures in 100F weather qualify as extreme. Coolant is a relatively 'cool' 180F

Exactly what I was saying. Hot exhaust right under the intake.