Changing core plugs in situ 3.8 E Type

[Trevor Spero]

I have 2 leaky core plugs one on each side of the engine. I would like to know if it is practical to remove the SU's and leave inlet manifold in situ whcih would save a lot of time.
I appreciate that the exhaust manifold and downpipes would have to be removed.
The engine was completely rebuilt with new core plugs fitted about 16 years ago. I assume it is age that causes the core plugs to leak as it has only covered 27K miles.

Any information would be appreciated.

[PeterM]

trevor as long as its not the small cores or the one behind the starter the rest are probably accessible without removal of any ancillaries, remember give the centre of the flat core caps a decent centre dent to keep them in place

[Trevor Spero]

Thanks very much for your reply. It looks as though it might be pretty tight to remove the core plugs without clearing some space. The 2 main culprits are probably the most accessible. I intended to do all but the small core plug.
I was told that the core plugs leak because of age. Is this the case and if so how long do they last on average. I was going to remove the leaking ones and check if they had decomposed. Any views on this.

Has anyone replaced their core plugs without removing carbs and exhaust manifolds? The cleaning of the core waterway hole and space for the hammer
looks like a problem.

I am sure that once I start the job it will all become very clear what is necessary but it is good hear of other peoples experiences.

[1954Etype]

I think there are core plugs that you tighten in place with a spanner. David will probably know

[Dave K]

Don't know if you mean the Rob Beere core plug strapping kit? To fit the straps you have to drill and tap a hole either side of the core plug and then the strap holds the core plug in place because of its concave design.
I fitted them to my car when I rebuilt the engine and have had no leaks.
To fit them you need plenty of space to get a drill in and is best done with the engine out.

Dave

[Trevor Spero]

Thanks Dave,
I can appreciate that a strap across the core plug would prevent it falling out and this is very comforting, however I can't see that it would prevent corrosion if that is what it is from making it leak. It is not an option at the moment as I do not want to remove engine.
Will take a look at the Rob Beere website.

Still would like to hear if anyone has actually changed core plugs in situ and how difficult it was for access.
Thanks

[david muir]

Have strapped the core plugs , engine in situ, manifolds removed, using a small air drill .

david

[patteian]

Replaced 3 core plugs in situ.

My car came over from California, although the engine had been worked on the core plugs, at least some of them looked at though they had just been put in with some hylomar but left as is and not flattened. Plus there was a very low coolant/water mix, little to prevent corrosion.

The issue I had was making sure the new one was flattened well and to do this properly you need to access it square. Getting the old ones out I used a long screwdriver to puncture several times and then lever, obviously you have to be very careful. If you had a long flexi shaft drill it may be better.

Regards

Ian

[christopher storey]

Strapping the plugs does not prevent leakage of the sort you are experiencing : its function is to prevent the plugs falling out under racing conditions when excessive block flexing may occur. I have changed plugs with the engine in situ, both of the 4.2 tub type and of the 3.8 dished type . The tub type should be possible to change without removing the carburetters provided that you remove the air filter box, using a longish piece of wood to act as a drift when you hammer them in. The earlier type are a bit more difficult and I think you will need a long bar to hammer to spread the dish sufficiently. Whichever type you use, modern thinking is to use an epoxy adhesive round the periphery to provide additional sealing

[Dave K]

Strapping the plugs does not prevent leakage of the sort you are experiencing : its function is to prevent the plugs falling out under racing conditions when excessive block flexing may occur. I have changed plugs with the engine in situ, both of the 4.2 tub type and of the 3.8 dished type . The tub type should be possible to change without removing the carburetters provided that you remove the air filter box, using a longish piece of wood to act as a drift when you hammer them in. The earlier type are a bit more difficult and I think you will need a long bar to hammer to spread the dish sufficiently. Whichever type you use, modern thinking is to use an epoxy adhesive round the periphery to provide additional sealing

When using the strapping kit you don't need to dent the top of the core plus because the shape of the strap keeps the edge of plug tight against the block recess stopping it leaking. I used red Hermatite around the edge to seal as a belt and braces approach.

Dave

[andrewh]

Strapping the plugs does not prevent leakage of the sort you are experiencing : its function is to prevent the plugs falling out under racing conditions when excessive block flexing may occur. I have changed plugs with the engine in situ, both of the 4.2 tub type and of the 3.8 dished type . The tub type should be possible to change without removing the carburetters provided that you remove the air filter box, using a longish piece of wood to act as a drift when you hammer them in. The earlier type are a bit more difficult and I think you will need a long bar to hammer to spread the dish sufficiently. Whichever type you use, modern thinking is to use an epoxy adhesive round the periphery to provide additional sealing

I just popped a core plug out when I accelerated on one of my first trips. Irritating and made a right old mess. Anyway, mine being the early type spredding dish , I was wondering what epoxy adhesive one is thinking of when sealing these in? I found the core plug in the engine mounting bracket so can have another go at getting this right. I had given them all a good old belt in the centre and none of the others had moved at all.

[christopher storey]

I use araldite rapid . You do need to clean the mating surfaces thoroughly if it is to work properly

[andrewh]

Thanks Christopher. On examination, I think I was a bit soft with flattening this plug out . Anyway refitted now and hopefully it holds. It gave away when I put my foot down which is surprising as I would not have thought there would be that much increase in pressure. I wonder if I had am air lock whether that may have caused the problem. Well the problem was I had not belted it hard enough. I have now!

[David Oslo]

Andrew

Have a read here, the manufacturers instructions on how to install welch plugs. In short, if using a ballpein hammer (as many do) it should be the flat surface and not the ball being used. Alternatively a large diameter round bar with flat (-ish) end, whacked with a mallet.

http://www.hubbardspring.com/install_reco.php?cid=45

btw : fingers crossed that you have decent access to the leaky plug...

btw 2 : may be worthwhile going over the other plugs too, and get them nipped down with round bar tool, for peace of mind

[andrewh]

Thank you David. Very useful article, which I wish I had read whilst the engine was in build. Now I cannot get the best flat impact so I am going to have to hope I have done the job . I did as you said earlier and checked all the others. The culprit was the front one right behind the distributor. It could have been worse. Anyway will get some coolant tomorrow , fill the engine and go for another test.

[David Oslo]

Thinking aloud ... did you prize out the leaky plug, discard it, and replace it with a fresh one ?

Me thinks that is the safer route, rather than trying to re-seat and re-seal one that has already had a blow, and thus has a certain deformation already.

[andrewh]

I re used the plug that came out. However it had very little damage to it which made me think I hardly hit it at all. I can stake it as per the article you pointed out so may do that. To be honest without the engine out of the car it is hard to do the job properly. I had assumed that natural corrosion would help seal these and eventually lock them in. Shame but hopefully I can sort it and move on

[David Oslo]

Natural corrosion. The rapid-set variety or the 1 hour version :D

Just remember to add a dash of salt to speed things up !

Oh, and getting a bit serious again, have you considered to use a bottle or two of Bar's Leaks in the coolant fluid. Added security on the inside if you were to get a mini-leakage, whilst waiting for the 'Natural Corrosion' to do it's stuff on the outside.

[Moeregaard]

I used a can of Bars Leaks to seal up the rear core plug on my '65 FHC, when it started dripping immediately after I reinstalled the the engine. It cured the problem immediately. I'm not sure if it's fact or fiction, but I've heard that Jaguar and other makers did this to cars before they left the factory.

[andrewh]

Thanks Guys. Just covered a quick 80 miles with no problems so hopefully sorted. I did use some K seal which I have used with good effect previously. I have certainly heard of manufacturers using Bar Seal as well. .