Rear core plugs

Is there a possibility of replacing the water plugs without having to lower the engine?..mainly with the one at the back
…I understand that it has 6 on the side and one in the back…or am I missing some…


I think the bad news is the one in the back cannot be done without lowering the engine. Exhaust manifold side ones can be done by removing the manifolds. When my shop did a complete engine overhaul (3.8S) they lowered the engine less generator and carbs, out the bottom. It might be possible to lower it enough to gain access to the rear core plug without removing the carbs and generator. Others might know. Meanwhile maybe some Bars Leak will work.

I have replaced the rear plug without lowering the engine however it is an LPB. You have to remove the water pipes for access to the plug. I replaced plug with a Dorman expandable copper plug using copious amounts of sealant. You have to bend throttle shaft towards the firewall as it is immediately behind the plug. I never got the throttle shaft back to absolute straight but the bend does not seem to bother the movement of the throttle shaft.

So a Dorman plug, non-hardening sealer, prayer and a lot of obscenity seems to work.

Cincinnati OH
65 MK2

That’s what I was seriously thinking about, looking for a way to place an expandable plug…do you know what the size of this type of plug would be?

From the ebooks
3.3 - Dorman Freeze Plug Replacement ( Paul Saltwick, May 6, 2004 )

The part number is DC-11, 1.75" expanding copper core plug.

Yes, Dorman has a website that lists distributors.

NAPA is one that sells over the Internet.

The plug should be a snug fit in the block and not driven in.
They can be turned down with a driven socket against Emory paper.
If you need to do this for a blown out plug, make another the same
dimension as a spare.

I use epoxy sealant on the edge.

You only turn the nut 2 turns. Directions are on the bag, however
they are often sold in bulk.

You may need to grind down the acorn nut crown on the rear plug
to clear the throttle linkage.

Installed correctly they will hold a 7 psi radiator cap.

Joel adds on Jan. 25th, 2005:

NAPA has them, part #600-4029. Cost is around $4. You can also
buy them off NAPA’s website:

Off the top of my head I don’t remember (I think it was 1 ¾ inch) as it was several years ago. But it was a standard Dorman size. You can check the parts catalog to see if the rear plug has the same part number as the main core plugs on the side of the engine.

Good luck!


George Leicht

US Bankruptcy Trustee (Chapter 7)

Reply to

PO Box 602

Batavia, OH 45103-0602


doing an inspection to see how the rear core plug is…apparently it doesn’t have a water leak yet…but water or oil comes out of these 2 screws or nuts so it is wet…does anyone know what’s under these? screws???

In the foreground you can see the acceleration bar…but below it…there is the other black nut just like the one shown…