Date: Fri, 27 Dec 1996 13:30:04 -0800
From: Mike West <mwest@cdsnet.net>
Subject: The Dummy Jug, Tool

Making a dummy jug.

Somewhere in one of Bobs Sermons is reference to using a dummy
jug. I can't find it but it's there.

Like some of you, :-) I shined it on at the time.

Probably in the "free horsepower", I read those a lot.  :-)

So what is it? Well it's an old jug you cleaned up and have
used for several tasks.

My first need was a cut on the sealing surface of the head.

Had to get down in there and grind it out with lapping compound.

Then I had to bring the rest of the surface down to that so I
also have a dummy head that fits in the dummy jug.

Put a push-rod on it for a handle and you have a four-0 lapping
tool for the whole flat surface down in the combustion chamber.

It might be called the "poor boys fly-cutter".

Then on my funky old case that looked like it had caught fire
and they put it out with an axe and a sharp screw driver, I had
to clean up the spigot surfaces with some more lapping.

At this point you find they have a 3/8 wide sealing ring on the
jug where it goes down in the hole. Have to take that down so
the dummy jug will slip in without force.

My third reason for having one has surfaced when I put all the
long/short rods on in random fashion based on the silly premise
that the rod should fit the crank.

Yeah there's different size crank surfaces too, including width.

Those damn tolerances we talked about.  :-)

More in the rods than the crank.

So I still need to check this whole mess against a standard
length cylinder. One jug will have to be used in all four spigots
to finalize the stack ups that show as deck height.

Thus one more use for the dummy jug.

Once that's all "spocked" out I can determine the spacers and
where each of my pistons go and where each of the jugs go.

If I used one of the new ones I'd be pressing it in and prying
it out of all four holes.

Come to think of it I can use my dummy piston too.

Wouldn't want to scratch my new ones.

On lapping spigot faces: use some bluing first and see how the
seal surface looks, if you have 80% and no cuts across it,
leave it be.  If you take some off one then take some off the
other the same amount.

Want to keep the head from being cocked.

To make the dummy jug, you just have to take a few thousandths
off the shoulder that slips into the spigot.

Do it in a lathe if you're one of those but it has been done
with a file or belt-stick by hand. Mine for instance.

The only thing left is to paint it.

Maybe a nice high yellow to keep some oaf from lifting it.

Tape the lapping surfaces when it's being stored to prevent
rash. Oil the bore maybe and store the dummy piston in it.

west