Another Telltale Question

[antique fisherman]

I have a 66 Chrysler 50hp. It has a welsh plug behind the t'stat. Would I have to remove that plug and thread the hole or can it be done in the plug? What about the metal slivers when the hole is threaded?

 

[Mark42]

Re: Another Telltale Question

The small amount of metal slivers probably won't hurt anything. In fact, when I changed the thermostat last week in my 85 hp, there was sand and bits of seashell in there. So the water pump is always pumping silt and stuff through the power head.

Depending on the size of the plug, you can either thread it, or if its big, like 1 or 1.5" wide, just drill another hole and tap it in the same area.

If you really dont want aluminim slivers in the motor, I guess you could drill the hole and tap while the motor is running on the hose/muffs so there is pressure blowing out the hole. Kind of messy, but it would work. The other option is to remove the thermostat cover and clean out whatever falls inside.

Btw, if you use grease on the tap instead of cutting oil, most of the cuttings will stick to the grease in the valley of the tap.

 

[BuzzStPoint]

Re: Another Telltale Question

x2 to the grease..

We've done this on automotive engines.
Load it up with grease and have a shop vac as you cut the threads.

 

[Frank Acampora]

Re: Another Telltale Question

Your engine has the head cooled by a simple tube running down it. This tube is cast into the head and the welsh plug simply closes the end. Cheap and fast for the factory. The plug is thin sheet metal and will not take threads. I'm trying to remember though if a pipe plug will block the inlet. You will need to examine before removing the welsh plug.

If you want to remove the plug and thread the tube, you need not worry about chips. They will flush out the first time you run the engine, or use a hose to clean out the tube before running.

However: One caveat--the casting is thin and you may not have enough meat to thread it.

You can, however, substitute a later type head from a 35, 45, 50, 55 with a full cover plate. 35 head might need a bit of relieving though because the bore on that engine is smaller. These heads already have a stainless 1/8 NPT plug threaded in them and do cool a bit better.

 

[Mark42]

Re: Another Telltale Question

x2 to the grease..

We've done this on automotive engines.
Load it up with grease and have a shop vac as you cut the threads.

This trick also works with drill bits. But its important to know the depth or thickness of the material being drilled. Measure on the drill bit and wrap tape around the bit at a depth just a 1/16" or so less than the thickness of what is being drilled. Then when that depth has been reached, remove the bit and pack the "valley" of the drill bit with grease, and then make the final cut through the material. Most shavings will be pulled up and into the grease and not fall through the opening as the bit cuts through. Some will drop, but most comes out on the bit.