Welch Plugs
Welch plugs (core plugs) are circular discs that fit into, and seal the casting and machining holes in the Engine block, Cylinder Head and Transmission.
Terminology
The Welch plug was originally designed circa 1910 by the Welch brothers☁ at the Welch Motor Car Company of Pontiac, Michigan. You may hear them called "welsh plugs". See Patent No 1058210☁.
They are often called "freeze plugs" because if the engine coolant freezes they'll be pushed out of the casting. However, the purpose is not necessarily to solve freezing problems but rather to seal the holes left by the casting or machining process (core plugs). Those that are designed for freezing safety may be called "expansion plugs" or frost plugs.
Set
Sets are for the engine block only (does not include the Cylinder Head plugs).
PLUG-WELCH A10/A12/A13/A12A/A14/A15 (see Block_&_Pan_Part_Numbers) 11019-32200ᴳ 44 Ø CAM bore, rear 00933-15000ᴳ 50 Ø CORE block, rear 00933-13500ᴳ 35 Ø CORE block, side (3) * NOTE: M2 Block reportedly uses 25mm plugs
Some sets include: 11021-13200 PLUG-taper (12.7ø) (fixing [cam] oil gallery) (2)
Pioneer PE-130 (PE-130B contains four brass plugs for the water-contact plugs + one steel)
Pioneer includes front & rear oil gallery blind plugs
REPCO 058-4030 Expansion Plugs for A12, A13, A14
DORMAN 557-031 A12 & A13 engines
MAFCO 437 120Y 1969-1972 (http://www.mafcobell.co.uk). MAFCO have got the name and years wrong, and one plug appears to be the wrong size
Cylinder Head
One Welch Plug:
- 00933-14000 PLUG-WELCH (1) head, rear [40 mm]
Engine Block
B110
Five Welch Plugs (including three on side of block)
Two on REAR: Large core plug + smaller cam bore plug
* 11019-32200 PLUG-WELCH 44 Ø CAM BEARING (1) block, rear (44.425 Ø) [1-3/4 inch] * 00933-15000 PLUG-WELCH 50 Ø CORE HOLE (1) block, rear prev. 01648-00084
Three 35mm core-plugs on manifold side
* 00933-13500 PLUG-WELCH 35 Ø CORE HOLE (3) block, right side
B120
35 mm Expansion Plug 00933-13500/11021-E3000/00933-1351A Nominal Dia.: 35.21mm Steel Height: 0.380"
プラグ (35mm - 3 required) 7510-8506 00933-13500 8506-8706 11021-E3000 [11021E] 8706- 00933-1351A
Cam bore plug 11019-32200 44 mm -8506 01648-00191 8506-
Transmission
Three Welch Plugs
- 00933-11400 PLUG-WELCH TRANSMISSION CASE (2) inside bell, northwest of mainshaft 14mm diameter, all 56-series and 60-series
- 32102-18000 PLUG-WELCH TRANSMISSION CASE (1) inside bell, below mainshaft
The two small plugs can be seen in this photo, to the left of the spring:
https://i297.photobucket.com/albums/mm219/ddgonzal/Datsun%201200/wiki/trans/TM-04_TM9.jpg
Removal and installation
Removal: tap one edge with a punch or chisel, then grab it with vice-grips and wiggle it out.
To install, fit squarely into bore, and tap gently and evenly into place. No sealer is used.
Others
MAFCO 438 1972-1980
MAFCO 441 Sunny 140Y 1980-1982
above looks to be for L14 engine PB210 (140Y in South Africa) - L14 engine 11021-21000ᴳ PLUG-welch [6 total, 40 mm] * (3) right side * (2) left side * (1) rear cylinder head * 00933-13500ᴳ PLUG-welch, 35 -7410 * 00322-13000ᴳ PLUG-welch, 30 -7410 * 11048-73403ᴳ PLUG-blind (2) 7411
¤