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MG MGB Technical - Core plug replacement

What is the procedure to replace the core plugs with the engine in the car? Can this be done?
Mike

M.A. Barrera

Mike. The three core plugs on the right hand side of the block are only very difficult to replace with the engine in the car. The one at the rear of the block is almost impossible to replace with the engine in the car. If the current plugs are leaking, consider replacing them with one of the 1 5/8" copper expandable plugs until such time as you can pull the engine, remove the remaining plugs, throughly clean the plug recesses, and install new factory style plugs into the engine.

Les
Les Bengtson

The back one can be replaced in-situ with the 'Betson Bolt', see http://mgaguru.com/mgtech/cooling/cool_105b.htm

I've also replaced one of the right-hand (facing forwards) ones, without removing anything else from the engine as I recall. I would have said that these three are relatively easy to do even if you have to remove the distributor/oil filter/alternator. Is that the oil gauge sender in front of one? If so it's an extra item you might have to move.
Paul Hunt 2

Chris Betson also has photos of removing and replacing core plugs in his web site;
http://www.octarine-services.co.uk/enginebuilding.htm
See step 7.

A few days ago there was a thread on the MGB Experience about a member having his engine rebuilt by a shop with a good reputation. When the engine was started one of the core plugs came out. He showed a photo of the plug that came out. It looked like it was installed with a center punch, it was a small dent and was looked to be 1/4"-3/8" deep. Going that deep will shrink the plug and it comes out easily.

Clifton
Clifton Gordon

Clifton, that was me and it was the rear core plug, 5 minutes into the initial break-in period! I want the shop to replace the side plugs too. This being a more technical forum, I thought this a better place to ask about technique and feasibility. I'm going to have them use the bolt and washer technique for the rear--I don't want to remove the engine.
M.A. Barrera

I'm sorry, I should have noticed. Hope you get the problem solved without having to remove the engine.

Clifton
Clifton Gordon

Mike. I have replaced the core plugs with the engine still in the car. That is why I no longer recommend doing so. Getting a good swing on the hammer is difficult with the three plugs on the right side of the engine. Possible to do, but you have to remove a lot of items (so you do not damage them and to allow getting a hammer and drift in there), then replace them.

Yes, you can use Chris's bolt method of installing the rear core plug. I use a version of it to guarantee that the rear core plug cannot pop out. But, using it to install a core plug is a different procedure--one which works best the second or third time it is used. You have to apply sufficient force, through the bolt and washer, so that the core plug is deformed properly into the bore and provides a good seal. All without being able to get a good view of what you are doing. Not a fun job and one which can be difficult to get correct on the first try--too little and there is a leak, too much and there is a leak. Great fun, but not when you want to be able to drive the car without worries.

Les
Les Bengtson

A few years ago a buddy and I had repeated problems with his core plugs popping out. The ones on the side we eventually got to seal by using an 'air chisel' with a 'plannishing hammer' bit. Think of a mushroom head on a long shank. It took just a couple of blips of the trigger and they were set properly. Even looked like the factory dishing when done. They haven't come out since. Don't remember how much we had to remove (if anything) since we weren't swinging any hammers around.
HTH.
Tom
Tom Sotomayor

Tom. An air hammer would be a splendid thing to use in situ. Except for the rear plug which would present more of a problem.

Les
Les Bengtson

Well, Les, that's a lot to ponder. The side plugs did not leak during the short run before the rear blew. I don't know if the rear was leaking before the event. I may just turn to good old JB Weld, strategically applied aroung the plugs on the side. My car is not going to be in extreme freezing conditions. After all the time and effort to put the car together, I really don't want to remove the engine. I know, it may be a crap shoot....

Have you ever used copper expansion plugs, www.dormanproducts.com?
Mike
M.A. Barrera

Wow, I posted without seeing Tom's. That sounds very doable without removing as many bits from the engine. I have to look for the right bit.
Mike
M.A. Barrera

I'm in the way back machine on this one so bear with me. I have used a core plug tool"that almost worked around corrners", the driver end had interchangeable size pucks with a lip that kept it from going too far into the block, the driven end was a solid bar[about 18" long] with a ball joint on the driver end, allowing severe angles of attack.
Put the plug in place, select the right puck, assemble the tool, place it in the plug, hit it with the big hammer you keep in the bottom draw.
As I remember it was a SNAP-ON tool and it worked very well but we are in the way back machine after all.
Ric
RIC LLOYD

Les,
That's where a 4" hole saw comes in real handy. Just kidding!!

For the rear plug we ended up using one of the rubber expansion plugs. Had to do a bit of modifying to get it to fit IIRC. Couldn't tell you now what we had to do to make it work. Too many years and projects in between to remember!

Tom
Tom Sotomayor

Well, I got one of the copper expansion plugs, too thick to fit between the engine and the back plate. Could not get it the hole in the block. Would have been a nice fix. These plugs would look nice on the side of the block. FYI picture.

M.A. Barrera

Wow, that's not the picture I intended to post. But, that is the right side of my engine.
M.A. Barrera

Looked again, right picture now. ??????
M.A. Barrera

I had a similar experience some years ago with a rebuilt engine, (by someone with a good reputation)when a side core plug blew out within days. He fitted a new one in situ. But I could not trust the rest, and I lifted the engine and changed the full set. When your as full of doubt as I was, I don't think you can put that rear one in without seeing it good and properly tight in the block.
c cummins

CP,

I am having the same feeling about this, but this an untested drivetrain. Rebuilt engine, carbs, rearend, clutch, tranmission and overdrive. I want the entire system to go through a 'shakedown' cruise. If I take the engine and trans out, fix the core plugs, and reinstall the whole thing just to later find that the clutch or transmission are not right; that would be just too much.
So I want to get the car on the road with the Betson bolt fix. Then, after all is well, think about redoing all the plugs with the engine out.

Mike
M.A. Barrera

Mike,

I just had the similar situation, a rear core plug that started leaking with less than 1000 miles on a rebuilt engine. The engine rebuilder made up a very simple tool (similar to the "Betson Bolt") which seems to have solved the leaking rear plug.

Email me your telephone number and I will describe the tool.

Charles Tregidgo
Charles Tregidgo

I built my own core plugs, aluminium made, an O ring ensure watertight, the part is fastened to the engine by three screws. I drilled and I tapered three holes in the block of course.
Regards

mw michel

mw, That is a nice plug.

Clifton
Clifton Gordon

I'll say they're nice! They would look great on the engine. A little beyond my talent and skill to drill and tap the block, however.

Mike
M.A. Barrera

Hi All

For 8 years or so we have been using thin aluminium flat bar strips to hold the core plugs in place. We use a small cap screw each side and a combination of washers to take up the gap behind the bar. The MG Factory did this on the works MGAs. We have, on occasion, seen core plugs fly out due to detonation problems. The setting of the timing is beyond my control if the owner of the engine doesn't visit us early! This way I have peace of mind. We haven't lost a block from freezing yet...make sure there is enough anti-freeze in the engine. We have done this since we had to use a cut down alternator to front plate bracket cut down and held in place while we bolted the rear plug in abot 9 years ago!

Peter
peter burgess

Illustration of what Mr Burgess says.
Regards

mw michel

Update, I did a modified Betson bolt, used a nut instead of threading a washer. Started up and ran for 25 minutes at between 2000 and 2500 rpm. No leaks and no drama. Peter, I have your book on MGB engines, I wish APT would have used these safeguards on my engine.

Mike
M.A. Barrera

This thread was discussed between 29/08/2007 and 13/09/2007

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