Drains in a 454ci carb'd Merc?
 

Going to be winterizing this week. Cant find anywhere that has where the location of the drains are for the block and whatever else i'll need to get the water out of. Anyone have a list?

1 drain on each side of block near motor mount, drains in manifolds. I usually pull the hoses off the lower water fitting and drain the block. You could just run until it is warm on hose and put 5 Galons of non tox antifreeze in with a winterizing tank attached to either drive or whatever water intake there is... The way I make sure the thing won't freeze is to check the fluid from the exhaust with a refractometer to make sure of it's freeze point.
If removing the block drains make sure to push a screwdriver in the hole to get out sediment. BBB

I was checking out the port side block drain plug (454 Mag) recently and wondered if that would be a good place to install a pressure line for my mechanical water pressure gauge. I currently have it running off the intake manifold jacket but want to relocate the line to remove clutter from engine topside. I pulled the plug and did notice some sediment; if I clean it out would that be a good choice for water pressure readings? I don't otherwise use the drain plug.

It will work at the block drain. Thats where mine used to be on my Pantera. The first foot of tube would clog up on a regular basis though.

Griff -
When you say "regular basis" do you mean like once a month or once a season? How did you unclog it? Do you think this would be a good choice for the pressure tap? My main resason for wanting to move it is that I don't like a bunch of brass adapters and fittings in clear view.

What about the port in the heads?

It would vary. It would stay unclogged for couple months and then would clog back up the next 2 times out. It doesn't take hardly anything to clog that 1/8" tubing.
For unclogging, most of the time I could just take the tube off at the engine and tap it/flick it with my finger and the sand would come out. I also had very thin wire that would help. The tube was clear enough that you could see the clogs. I did have replace the entire tube once because I left it clogged at the end of the season and couldn't get the junk out of it.

Exactically !
You could plumb the intake manifold and put fitting in rear of motor, or even drill and tap the rear of the block and hide it. BBB

When I replaced the tube, I actually drilled the fitting so that I could shove the tubing about an inch into the block. That seemed to help a lot.