TR2/3/3A Aluminum Plug in Head

Hello All,
I had a coolant leak coming from the plug on the top of the head. I had ordered a replacement from TRF, after removing the old one I found the threads very corroded. The reinstall didn’t go well. Does anyone know the thread pitch? Size? I’m guessing 3/4 standard? But seeing as it’s a pricy tap, I want to get it right. Thanks so much.

I was waiting for somebody with the answer to chime in. There was a similar question on either this forum or Triumph Experience forum. I believe they had the answer but also stated that they had converted to a steel or iron plug with a conventional thread. You should try search the forums for the answer.

Thanks Charley, I searched the threads, didn’t find the answer I was looking for. I did get ahold of the tech at Moss.

The plug is 1” 14NF. Rare, but not impossible to find. I got a tap off amazon for $30.

I didn’t want to change threads or metals. It was easy enough to get parts I needed. I will say TRF has the plug for $5. Moss charges $20.

May I ask what is the procedure in replacing / installing a new plug. Mine Shows signs of leaking so I need to address this. Do you use some type of sealant on the threads and how do you tighten the plug, what tool?

I am not sure what happened to my plug. I had the head hot tanked and other work done on it. When I picked the head up there was a steel plug in the hole that sticks up some. The shop deny putting it in and I do not remember what was in before they put it in the tank. I have tried to remove it without sucess so it could be a standard pipe plug they jammed in there or it may have been there all along. It does not leak so I am leaving it alone.

David

The plug is aluminum. It is also threaded in, but chances are really good you won’t be able to unscrew. The most common method I uncovered was to just strike at it with flathead and a hammer. I did this, came out just fine. My problem once I exposed the threads was how full on funk and corroded they were. I tried my best to clean out with a craftsman dental pick, but didn’t get far. The problem I kept running in to was the aluminum plug is too soft to screw in on bad threads. The threads would dig in to the threads, when it would catch it was way too easy to strip the screw bit on top. (The old way of doing it was probably way more effective. They came in packs of 5 in a stack. You would basically just screw it in until it broke off and file down what was there).

I am using thread locker to keep the plug from leaking. Permatex 56521. It’s safe with oil and antifreeze and heat. Should cover all the angles. As I mentioned I found a 1” 14NF tap on amazon. It’s a beast. I’ll clean up the threads, Cake the aluminum plug with thread locker, screw in place as best I can and hope for the best.

David, I was told that was an option, but best to do when hot tanked. The plug melts out in the hot tank.

I just used a an iron plug. Been driving like that for 15 years and never had a leak.

Did you have to rethread?

HighAltitudeTR3 said:

Did you have to rethread?

Click to expand...

From what I understand, the common replacement is a 3/4" x14 NPT tapered pipe plug. You can re-tap a bit with a common pipe tap. Probably best to use a socket head plug.

There are several of those aluminum plugs around the engine. The front and back of the oil gallery come to mind. TRF sells the aluminum plugs as a "stick" with several lined up, and a hex at the end. You have to drill out the old plug, run a tap through the threads to clean them out, then use a good bit of thread sealant as you thread the long stick into the hole. Once the first plug is installed, you cut off the remaining stick with a razor saw, and move on to the next hole, and the next plug on the stick.

Once cut off, a quick pass with a file makes the plug look just like OEM!

HighAltitudeTR3 said:

Did you have to rethread?

Click to expand...

I just installed the hex head plug. I did not tightenthe plug down very deep. The plug stands out quite a bit but my intention was to just fix the problem and I was not worried about cosmetics as you never see it until the valve cover is off. If your cylinder head is off and you want it to look proper do what CJD suggests.

Earlier Thread https://www.britishcarforum.com/bcf...ifreeze-on-the-top-of-the-head&highlight=plug

HighAltitudeTR3 said:

David, I was told that was an option, but best to do when hot tanked. The plug melts out in the hot tank.

Click to expand...

yeah, as soon as I saw "aluminium plug" and "hot tank" in the same sentence I figured that caused the failure.
I could tell you stories.....rocker shaft supports, rear main upper half retainer.....oh well.

Same here. I once paid a couple hundred $ for fancy titanium valve retainers...back when titanium was not as common as today. I later sent the head in for a valve seat touch up and they had hot tanked it. The retainers completely dissolved. I almost cried when I realized the shop had cost more than they were making.

On 49-53 Ford flathead V-8's there is a half rear main rope seal retainer that taps into the block. The number of times the shop kid doesn't understand "complete teardown, then tank" has happened....not to me, I send them in bare, but every block I have scrapped due to excessive cracking over the last 55 years, I have saved those.....in a box on a shelf....shops call in a panic, I have one.

Is it FE Series big block Fords have aluminium rocker shaft standoffs.....hot tank, they're gone.

Didn't know that about Titanium....better not put Titanium bits into my old motors.

Good thread. Wish I found that first. If I can get a good deal on the Aluminum plug, I’ll go this route. Thanks