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Core plug replacement woes

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DaveA

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Help! I need some suggestions. While I was trying to replace the weeping middle core plug on my MGA 15GD engine something bad happened. A piece of the block broke off. About a 1" portion of the inner "shelf" where the core plug sits broke off and dropped into the block. I've managed to get the broken piece back with a flex magnet. But, what now?

I'm wondering about trying to grind off the rest of the "shelf" and then fitting a rubber expansion plug. The only other thing I can think of is replacing the block.

Has this happened to anyone else?

Thanks for any tips.
 
I would have fainted Dave! There are fixes though. For an immediate fix go ahead and use one of those rubber thingies, but promise me that you won't get slack and leave it in there. Once the car is mobile again run it by SEVERAL welding shops and ask if they would look at the position of the hole and ask if they would braze the piece back in place if you brought the car over on a trailer with all of the coolant drained and the area dried out. It will entail gradually heating the area around the opening and some fairly experienced hands at doing the actual brazing, but it isn't rocket science. You might want to pull the distributor and generator to make it easier for the guy to get to the opening. Once the piece is back in position you can take the lump home and use a Dremel tool to approximate the original shelf. With some real care and several grinding stones you can do it. Then when you drive the new plug back in use some Permatex and pray a little. I would be surprised if the whole thing cost more than a hundred bucks including a new Dremel tool, but that would be FAR superior to either replacing the block or removing and stripping yours for a fix on a bench. BTW: It sounds like your block MIGHT be suffering from some internal corrosion after all of these years. I would suggest that you take some really special care when replacing the other plugs. BTW..What did the inside of the plug you took out look like? If it showed significant corrosion it might be a good idea to go ahead or at least make plans for the replacement of the others. If the inside looks okay then let sleeping dogs lie. Anyway, if you do have to replace the other plugs drill the center out with a 3/8 or 1/2 inch bit and grind the rest away with a Dremel tool until you have just a thin ring left. Then use a sharp chisel driven with care and some dikes to cut and drag the final remains from their beds. Merry Christmas! Jack
 
Dave, welcome aboard, firstly.
I don't think you really have a problem. I've had blocks like that, or ones where the shelf was nearly corroded away. If you can use a cup type plug, clean the surface of the block very well, and coat the mating surface of the plug with a good sealer, such as Permatex Aviation Form a Gasket, #2.
Tap the plug home, concave side out, and you should be good to go. I usually run a thin bead of clear nail polish or the like around the outside edge of the plug, but don't know if it really helps or not. Just an old trick I learned years ago, and still do it.
Jeff
 
Thanks for the info guys.

Jack:
Well, I didn't faint, but the temperature in the garage definitely got hotter for a few minutes. I don't think I can use a rubber plug without removing the rest of the inner flange. There's little depth available between the outer hole and broken inner flange for the plug to grab.
Just thinking about leaning over the fender with a die grinder for hours is depressing.

Jeff:
Have you actually used one of the cup type plugs in a Brit enginebefore? Sounds like it may work but I'm a bit concerned that I won't be able to drive the cup in far enough before it hits the inner flange for the taper to really grab the sides of the outer hole. What do you think about buttering the back side of the cup around the circumference and the face of the broken inner flange with J-B Weld and then using some Permatex sealer around the edge. Or maybe just J-B weld all around. The engine's going to have to come out some time to really fix this but I like to not do it until next winter. I've got a 3 main bearing 1800 that could go in but it's in no shape right now.

Thanks again,
Dave
 
Dave, I've used the cup type plugs on several British engines, and they've always worked for me. I haven't done a 1500 though. I seem to recall there being cups with shallow shoulders, but I don't have any way to check on that today.
I would be careful with the JB Weld, as it may extrude into the coolant passage and create a partial blockage. Maybe if you let it set up a bit, and formed it flat on the surface?
Jeff
 
There are cups with shallow shoulders. I had to go to the parts house and was able to get into the back to go through boves to find them. Great to have a good parts house.

Bruce L
 
Dave, I just went out and looked at the four "A" Series engines I have in the garage. Half have cupped plugs, and half have the other style. Being they are "A" Series may not be relevant to your 1500, but I thought I'd look anyway.
Have you looked at the copper expansion style plugs?
There are a lot of options I would explore before I would consider changing a block for this.
Jeff
 
Bruce, I was certain there were. I'm lucky in that I have free rein at my local NAPA, since I helped start the business in 1975.
It's great to be able to go grubbing around in the back, ain't it!
Jeff
 
Hope you found a shallow shouldered plug Dave. If you can get a shouldered plug in there I would suggest this. Use your Dremel, don't leave home without one!, to clean the inner face of the hole so as to present as smooth a surface as possible to the rim of the cup. Measure the depth of the hole from the outer surface of the block to the remains of the "stop ridge". Take a measurement of the outer depth of the cup and compare the two distances and record it. Select a socket with and outer diameter only very slightly smaller than the inside diameter of the plug cup. Coat the outer surface of the cup with JB Weld and drive the plug squarely into the hole using the socket to make sure that it is driven in straight on. Drive it in in small increments until you see that the shoulder of the cup protruding from the block is equal to the difference between the cup shoulder and the hole boss depth as you recorded it. I would think that this would result in a very serviceable repair. Jack
 
Hi Jack,

I'm off to the NAPA store shortly to pick up a few of the copper expansion plugs and maybe roam the shelves looking for shallow cup plugs. They had to get the expansion plugs from the wharehouse but should be in this morning. They couldn't tell me anything about the depth of the cup plugs so hopefully they'll just let me look around. But if I can't find anything the expansion plugs are considered a "permanent fix".

On another topic... My wife and I are considering western NC as a retirement destination. We have been thinking about the Boone, Blowing Rock, Lenoir region of NC. We will be making a swing through the area in March when we visit some friends in FL. Are you a native of the area? Any tips about good retirement cities?

Thanks,
Dave
 
Pardon me for jumping in, but for retirement cities, you might also want to investigate Hendersonville and the general area around asheville. I think the weather may be milder. I'm not sure, but I've had two or three people tell me that they're going to retire there.
 
Let's switch the retirement/where to live issue to an OT post. I'll do it right now. JAck
 
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