51 8N - Freeze Plug (I think)

Matthew H Stockton · Apr 29, 2013

I have a 51 8N. I went to get it ready for the season. Checked the radiator and it was low (really low - I know the level should just cover the coils - there was no visible coolant). I added coolant; while adding I heard a falling water sound. Looked around and water was pouring out of the "driver" side engine block. On closer inspection just forward of the oil filter, is/was a plug. It appears it had been filled with something (JB Weld?) other than a metal plug. Anyway that something has given way and their is a hole in the block. I cleaned the hole with a wire brush on the end of my drill. The inside diameter is about .91 inches. I need to know how to plug this. The surface of the hole (perpendicular to the crank) is fairly rough, so I don"t know how a metal plug will seal. I tried a rubber expansion plug, which blew out.

I have uploaded a picture of the hole.

I would greatly appreciate some guidance here.

souNdguy · Apr 29, 2013

drain the water a lil further ... dry the hole,, clean it with brake cleaner or alcohol.. let dry.. get a core plug and some permatex #2. coat the ID of the hole good.. then put a smear on the OD of the plug. set the plug and dimple it.

I have seen some peole fill them with jb welde and sand down to fill the pits.. but I'd try the permatex first.

Bob · Apr 29, 2013

Plug is 1-3/16 Welch plug... you should be able to get one at any REAL auto parts store.

As Sounder said, it will be convex as installed, and when you flatten it, it expands and locks in place.
Correctly installing a Welch plug

Matthew H Stockton · Apr 29, 2013

Awesome information from both of you. Thank you.

36 Coupe · Apr 30, 2013

Looks like the remains of an old plug in the hole..91 is too small for that engine.Put a good coat of permatex #2 on the inside surface of the new plug.Rubber plugs are worthless.

DollarBill · Apr 30, 2013

The objective is to flatten the Welch plug so that it spreads out and jams in the hole:
1. Ensure the block is squeaky clean.
2. Coat the block with Loc-Tite before installing the disk. (Permatex #2 is good too)
3. Use two ball peen hammers - One as a buck to achieve a flat hammer strike and minimize the possibility of striking the block.
4. The edges of an installed plug may be staked to improve retention.
5. Again, the goal should be an installed plug that is visually flat.
6. Use brass Welch plugs if you can find them. They are 1 3/16" diameter.

Alternative Solution

Dober_paw · Apr 30, 2013

Did this same job on my 52 8N sidemount last year - here's a link to the post I made at that time :

http://forums.yesterdaystractors.com/viewtopic.php?t=930005&highlight=

and if that doesn't work - its date/time was : Aug 08, 2012 8:40 pm Post subject: 8N Freeze Plug (long)

There's 4 of those plugs - If one's gone, the others are not far behind .

Good luck!

51 8N - Freeze Plug (I think)

Matthew H Stockton

New User

souNdguy

Well-known Member

Bob

Well-known Member

Matthew H Stockton

New User

36 Coupe

Well-known Member

DollarBill

Member

Dober_paw

Member

Similar threads