Coolant Change

[USA1LT1]

Anyone know where the block drain plugs are on a '71 SB. I was looking for something obvious but could not find what looked like drain plugs. Thanks for the help.
Frank

 

[Bob Chadwick]

On the side of the block on both sides right above the point where the oil pan attaches to the bottom of the block.

 

[USA1LT1]

Towards the front or back of engine. I did see what looked like a hex plug above the oil filter. What kind of plugs are they, do they take a socket head.
Thanks Again
Frank

 

[Bob Chadwick]

Frank,

As I recall they were just two pressed in disks about the size of silver dollars on each side of the block.

If you are just changing the coolant, I did not go through all of that. I just added a back flush kit to the heater line and ran hose water through the block to clean it out.

Bob

 

[wishuwerehere82]

Bobchad,

Those are the freeze plugs!

USALT1,
The drain plugs are small square head or hex. They unscrew to drain the block. They are little bitty things(1/2" dia.or smaller) on either side of the block, if that's any help.
Get a pan ready, they spew all over the place.

Pete.

 

[Bob Chadwick]

Learn something new. I didn't even know they had drain plugs. When I did mine the first time, everyone pointed to those plugs, used the term freeze and drain plugs interchangeably and told me I didn't want to mess with them.

 

[wishuwerehere82]

They were right, you don't want to mess with them.

 

[81 Corvette]

dumb question, do the early ones not have a petcock at the bottom of the radiator?

 

[wishuwerehere82]

They do, But there will still be some left in the block.

 

[JohnZ]

There will be a LOT of old coolant left in the block if you don't remove the drain plug on each side - those are at the bottom of the water jackets around the cylinder bores, and that's the only place you can drain them. You have to do both sides - they're not cross-connected. They can be a chore to remove - when you re-install them, use anti-seize on the threads to ease removal next time.

 

[USA1LT1]

That sounds about right. I have never changed coolant without draining the block. Half the coolant is still in the block. I changed the coolant in my 2000 Tahoe and that was a chore getting to each of the two plugs. My '71 should be easier but I just did not see them. I will look again this evening.
Thanks to all
Frank

 

[USA1LT1]

Found the drain plugs. You have to remove the shielding which is covering the plugs. The drivers side is easy with only two bolts. The pasenger side is a different story as one of the bolts appears to be behind the starter which may need to be removed to access the bolt. I will check on this over the weekend. The plugs have a bolthead of about 9/16".
Frank