MGB: generic freeze plug question

Are rubber expansion plugs as good as the regular metal plugs? I was helping a buddy work on his boat this weekend and one shot out the side. It's in a tight spot (which was probably why the PO used the rubber expansion). If not, the engine will have to come out.

TIA!

Absoultly not. If the rubber "plumbers plug" was in the water jacket, the heat more than likely got to the rubber, hardened it and made it shrink. They are only good for the application that they are designed for, low temp and low pressure.

You can get metal/copper freeze plugs that expand to fit. They have an acorn nut on the outside, and as you tighten it the plug will expand to fit the opening. I use done of these on the rear most freeze plug on my B. I found it at a local, non-chain auto parts shop, the one that local mechanics use. They are made by Dornan.

I checked an old post on the MG Owners BBS. The brand is actually Dorman "Quick Seal". 1 5/8" for the MG, BTW.

Dorman is the company alright, I've sold a bunch of them and used some myself, they work. Get on the phone a call around until you find a parts store that sells them. If you have a Fisher/Federated store where you live they'll either have them on hand or can usually get them out of one of their warehouses overnight. Fisher/Federated has over 3700 stores and I'm surprized I don't hear about them from you guys East of the Mississippi River. They started in Pennsylvania and are growing from there.

Thanks guys. I'll look for the metal expansion ones. This one has a large metal washer on one side, a smaller one on the other, and a nut that once you start to tighten will cause the rubber to expand.

What does the Dorman use instead of rubber?

where would freeze plugs go?

JDW: Now that you mention it , the local "good" parts store does sell Federated parts.
Steve: The plug looks like a "flying saucer", it has a dished convex side that when the nut is tightened is drawn towards the nut and this pushes the edges outwards to fit. I installed mine with just a light smear of Permatex No.2, but some use Hylomar.
John: The freeze plugs on the MG are on the side of block (the 1 5/8" round blank parts) and another on the back of the block. They are also known as core plugs or welch plugs. The stock ones are just dished shaped brass alloy disks that are fitted dry and then struck with a hammer to flatten them into place. I used the Dorman on the very last one on the rear side of the block since the space there was too tight to swing a hammer.

I'll probably know what you're talking about, but all the contours of my block have been smoothed over and reshaped with a nice insulating layer of dinasour poo :-)

like where they blanked out the mechanical tach take-off?

Copper. Ask for Dorman copper expansion plugs, freeze plugs or, core hole plugs. Freeze plugs go by all three names. Have them check the book for how tight to turn the nut. I'ts an acorn nut and should bottom out before you can get it too tight. I put some in my Studebaker Hawk about 1965 and they're still holding.

BUT, why not use the proper plug?? Place them in, whack them, and they are done like dinner!! They never seem to leak until they rust out!!

Time and space.

I would use the proper plug, except the motor is in the boat in such a way as it would make it almost impossible to get a good whack at them. I imagine that's probably why the PO used a rubber plug rather than the correct thing.

Unfortunately, I don't know enough about inboards to remove the motor. I know there's a trick to the prop section I don't think I want to mess with.

Well, just make something with an angle on it, and a long top piece!! If you can hold it and whack it 10% of the way up the shaft, it won't hurt to bad and it wil spread it!! You can do it!!!