And where is the antifreeze?

[Drakeule]

I was able to drain my '40 Roadmaster coupe's radiator, and then I drained the block. Of course, it came out with such force that it went all over the garage floor; I was able to capture some of it in a 5 gal. bucket. 

 

Now, the manual says that the cooling system holds 16 Qts., with about another 1.5 in the heater. That translates to almost 4.5 gals of antifreeze. I have just about 2.5 gals.

 

I know I lost maybe a gallon on the floor, so could there be residual coolant hiding in the system? If so, any way to flush further?

[Drakeule]

And yes, I opened the heater valve!

[Mark Shaw]

Yes, some coolant will remain in the water jacket "shelf" on the side of the engine.  Many Buick engines have cracks due to plain water  freezing in that area.  After driving in hot summer heat, many cars require regular topping-off with plain water.  This dilutes the antifreeze and makes it less effective.  This is another good reason to fill your engine with 50/50 antifreeze instead of just draining the engine for winter storage.  

[EmTee]

If the radiator is partially plugged there will be a certain volume that will never be filled with new coolant, or drained when the petcock is opened.  When I removed the radiator from my '38 for a re-core last winter it felt like it was full of Jello...

[Bloo]

How many drain plugs on a 320 engine and where?

[EmTee]

My '38 has one on the right side of the block between the front of the starter and the distributor.