Core Plug Install


Recently, three brass core plugs on my 1955 TF 1500, directly under the exhaust manifold, began to leak. The other 6 brass core plugs still seemed to be watertight. The engine was rebuilt two years ago along with a final restoration of the front at that same time. So, I was reluctant to remove the engine to replace the core plugs because I was worried about some damage to the restoration.  After doing some research on how to replace leaking core plugs I realized there were really no suitable options available to me that were considered permanent fixes. One fix, I read, suggested I seal the leaking core holes by using JB Weld. However, I did not want to rely on a sealant for a permanent fix. Others said to drill holes in the side panels of the engine area to slide a rod through for hitting the core plugs. And others said to remove the side panel and fender to gain access to the core plugs. None of these were options I wanted to undertake given the restoration work previously done. Which meant, I need to find another way to replace the core plugs.

I think the reason why my plugs began to leak is that, in part, they were not manufactured to the right size. This is not a disrespectful comment to the group that rebuilt my engine. They did a great job rebuilding my engine. I think they got core plugs that were not sized properly from their part supplier. The core plugs were installed properly along with a sealant at the core plug lip. But why did they fail after two years? More on this later.

In any event, I needed to replace the core plugs. To seat core plugs properly, you need to hit them in the center with a good wack from a ball peen hammer. However, there is not enough room in the engine area to swing a ball peen hammer and get a good dimple on the new brass plugs. That is when I thought of using my Sumake palm air hammer. But first I needed to make a ball peen head for the air hammer. I cut the threaded part off a 1/2" carriage bolt and use High Heat JBWeld to secure the carriage bolt head to the hammerhead.

I used High Heat JBWeld because it is a putty and wouldn't run all over while I waited for it to cure.

After having removed the exhaust and intake manifolds, I found the air hammer was small enough to easily hit all 7 core plugs on the side of the block, so I systematically removed them by row and used a right-angle Dremel with a wire brush tip to clean the core holes.

Then I used an old toothbrush with most of the bristles cut off so that just the tip could be used for brushing a small amount of High Temp RTV sealant around the lip of the core hole. Also, I used a mini ball peen hammer to seat the new core plugs before hitting them with the air hammer. Finally, using my Sumake palm air hammer with the ball peen head, I set the new core plugs in the holes.

I set the pressure on my Sumake palm air hammer at 125 PSI to get a dimple in the brass core plugs. I should note that the new core plugs came from Tom Lange at MGTRepair. His plugs are a tighter fit and are thicker making them stronger core plugs. I followed this procedure for all 7 plugs on that side of the engine.

So why did the other core plugs fail? This is just my theory, I can't be positive this is what happened, but I think the thinner core plugs that were used (besides being smaller in diameter to begin with) did not stand up to the heat coming off the exhaust manifold and thus failed over the two years to maintain a water tight seal despite the sealant at the core hole lip.

By the way, the other two core plugs (one behind the block at the firewall and the one under the camshaft cover) are not accessible with the palm air hammer. Fingers crossed that those stay watertight for a long time.

Just thought I would pass this method of replacing core plugs along. If you don't have a palm air hammer, it is worth the expense to purchase one rather than pay for the engine to be removed. You want one that can handle 125psi because you need the air hammer to make a good dimple in the core plug. Hope this helps anyone who wants to "replace" core plugs without the extra expense of removing the engine or causing damage to a restored finish.

-- Tony Rizzello

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