welch plug

[Anonymous-0]

what exactly is a welch plug anyway? what's it's it do?

 

[JerryCPP(WA)]

Welch plug is another name for expansion plug. There are three types: shallow cup, deep cup, and disc. The cup types look like a cup, and are driven into the hole in the side of the block using a socket and hammer, and held there by friction. The disc type is a concave/convex disc - the hole in the block has a ledge the disc sits on, convex side out. Then you take a ball pein hammer and smack it once in the center. That causes the disc to expand against the side of the hole. Both types are prone to rusting from the inside as they contact the coolant. You cannot re-use them, and it's always a good idea to remove them during overhaul. That way you can dig out the crud in the block, and put new plugs in.

 

[Anonymous-0]

thanks Jerry,i actually was refering to a carburator,didn't know an engine block had them also,but answers my question anyhow.

 

[supergrumpy]

same thing on a small engine carb, usually they will leave a disc shaped opening up top on the carb body when they cast them

after they drill the various upper passages they will put a real thin welch plug in and tap it lightly to seal it, drill the center and run a screw in just a bit to get them out

on lower parts of the carb, they have smaller opening, after they drill they will press a steel bb into the opening to seal it, bugger to get out without ruining carb, lower parts of carb collect most of the gum

guess they want to sell new carbs

 

[JDemaris]

To be technical, a "Welch plug" is a concave disc used to protect engines from freeze damage. The other types of "freeze plugs" shaped like cups are not of the Welch design.

Like many terms and words, this one tends to get used generically. I was tought early on the difference from what was called a Welch plug - and other types of expansion plugs. But, that was over 50 years ago.

The Welch plug was invented by the guys that owned the Welch car company in Michigan, and the original idea was gotten from sticking a coin into an engine coolant port - which later got patented to a concave disc.

 

[Paul from MI]

Actual purpose of "freeze" plugs is not to preveny block damage if coolant freezes. That will happen anyway. The holes for "freeze" plugs are there to support cores when the block is cast. The holes are then plugged with "freeze" plugs afterwards.
Paul

 

[msb]

The holes that welsh plugs are used in are where the inner molding core is supported during the casting process. After the block or carburetor or whatever is cast, the inner casting core is broken and taken out the holes. The freeze protection offered by welsh plugs are a secondary benefit and is not the primary reason for the holes.

 

[guido]

Hey Larry
Paul is wright. They also serve another function, if the coolant freezes they pop out rather then the block cracking, like a fuse in an electrical circuit. That is how they got the name.
Guido.

 

[jeffcat]

Yea the little disks in a carb. are called that. If you get a rebuild kit there should be one or two in there to replace the old ones. You VERY carefuly drill them out with a 1/8 drill and pry them out. Drill just enough to get through the metal of the disk. NO MORE. This will expose the idle jets in most mower and chainsaw carbs. It is worth doing cause it will not be particals in there but gunk or slime. Putting them in with the socket and hammer method works great. Just a little tap is all ya need. I put a very thin wipe of permitex around the edge to seal it well but it is not needed. Jeffcat

 

[dave guest]

I have removed and installed freeze plugs(so called) and welsh plugs and I think they are entirely different animals. Freeze plugs are friction fit and no peening necessary. Welsh plugs have to be worked into place sometimes by peening base metal over them. Freeze plugs may be improperly names but when the engine freezes, they always seem to pop out. Sometimes you have to make hold in floorpan or firewall, fender to install.

 

[Spook]

Yup! The blocks go thru a shaker that bounces the block around. The broken up sand core comes out the holes. A cast iron foundry is a noisy, dangerous place.