Fitting welch plugs with special internal fitting tool
ENGINE ASSEMBLY HINTS
Fitting Welch plugs and oil gallery plugs…… selection of Welch plugs will depend upon the application. Diesel engines should use stainless steel as erosion seems to be more prominent than in petrol engines. Brass Welch plugs are a good choice for most applications. The life of plain steel Welch plugs will depend upon the quality of the Welch plug and the maintenance of the inhibitor at the correct levels.
When fitting welch plugs ensure the block is not damaged. Emery finish the Welch plug hole if minor damage or foreign material is evident.(hard sealer or rust etc). Use a suitable sealer such as aviation gasket goo. When fitting saucer type Welch plugs such as the camshaft plug in some V8’s.use a solid flat punch to flatten 2/3’s of the dome area in the centre only. Don’t reshape from convex to concave, just go to flat as at this point maximum size and sealing pressure has been achieved. Don’t use the ball of a hammer to butcher the plug into submission as the quality of the seal will be suspect. SIMPLY NEATLY FLATTEN 2/3’S OF THE DOME AREA IN THE CENTRE, STAYING AWAY FROM THE SEALING EDGE.
Fitting cup Welch plugs…… Special tools are available to fit cup Welch plugs. These may be OK, but I have no faith in them. These tools rely upon contact with the outer edge or sealing area of the plug. If you look at a modern style cup welch plug you will notice that the sealing ring is only around 1 to 2 mm wide on the very outer edge. Any slight burr or mark on a tool that contacts the sealing edge will result in a coolant leak. These fitting tools may be OK while brand new but I prefer to use a good internal fitting tool. My advice is to never fit welch plugs using the sealing outer edge. Select a tool that has around 0.5mm. clearance on the inside of the cup. Use a good quality sealant. Squarely and firmly hammer the welch plug to flush with the inner edge of the fitting chamfer. This method has been reliable and has had 100% success against leaks over a 25 year period.
Threaded welch or gallery plugs…… These are very easily sealed with a good sealant. Don’t use thread tape.
: Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2020 UMR Engines www.engineproblem.com