William M Gilroy wrote:
>
> I have have received several suggestions about what could be causing
> the low compression in cyl. #2 and #3 in my 77 Midget.
>
> The only way to really tell is to run a leak-down test.
Well, that's not really the only way.
Personally, I would pull the head and inspect everything. That
will tell you all you need to know.
The leak down test is great to locate problems that might not
require anything, but your engine is going to require
"something", and that will involve pulling the head.
Really, not knocking the leak down test, it's useful, but
in this case no matter what it finds it'll involve pulling
the head. So... I would just pull the head and know for sure.
Inspect the valves for any non-round areas.
Turn the engine over until all the pistons are about
level. Fill the cylinders with diesel fuel, and see how
long it will hold the fluid. This is a "rough" test for
ring strength, you might find #1 and #4 will hold diesel
fuel overnight and #2 and #3 will leak it out before your
eyes.
> I tried the above but my connection at the spark plug hole was leaking
> and it made too much noise to hear other leaks (I think).
All you need to do the leakdown test is a blow gun with
a rubber conical tip. This is the same tip you use for blowing
out steel lines and so on. You can get a blow gun with all
the "fixins" for under $10, and the rubber cone is usually
in there.
Anyways, you can hold it in with one and and check with
the other, or get an assistant. Not as handy as the "purpose
made threaded air fitting", but you probably already have
everything you need.
> 1. How many PSI should I charge the cylinder to? (I used ~40 PSI)
Feel free to use a lot if it helps you hear. I use 90psi,
but this is an engine so it's use to much higher.
> 2. How fast should the air leak out?
Without a "fancy" gauge you have no real way of measuring,
but if you can feel it that's too much.
> 3. Will the volume of the cylinder affect this? If show how do
> I figure in the location of the piston in the cylinder?
The piston has to be at TDC anyways, or near TDC. This is
so the valves are closed, otherwise the cylinder doesn't actually
pressurize.
> If the head gasket is blown how will I tell? Will
> be obvious even to me :-)
Yap. It'll be ripped, or visibly scarred.
Normally gaskets have a hardened ring around the cylinders,
it will be visibly not right.
--
Trevor Boicey, P. Eng.
Ottawa, Canada, tboicey@brit.ca
ICQ #17432933 http://www.brit.ca/~tboicey/
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