Changing coolant

[blown motor]

I need to change the coolant in my 340. After I drain the rad should I remove the plugs, one on each side, that are just above the oil pan rail? Will that drain more coolant?

[71GranCoupe]

That will drain the coolant left in the lower area of the block. Depending how long the old coolant has be ran, there may be some buildup behind the plug that may need cleaned out as well.   

[blown motor]

@71GranCoupe am I better to just leave that alone and fill it with water and drop that out before adding new coolant.

[71GranCoupe]

Lots of variables. Is the motor the original that has never been rebuilt? If it has been rebuilt, how many miles on it and how long ago. How long did the coolant stay in the motor? Have the hex plugs ever been removed? What did the coolant look like when drained? If you choose to remove the plugs, be sure and use a six point socket or wrench as not to round off the high points. If there was some recent major work on the block before installation and not a bunch of miles on it, probably a good flush would be fine. It comes down to what you are comfortable with. Let us know what you do and how it goes.