Charlie,
The "official" tool for cc'ing a cylinder head is a burette. I think they are
well over $100, and very hard to find. I used a smaller device called a
pipette, which cost me eight bucks. Basically, a pipette is a glass tube with
cc markings on the side. Mine goes to 25 cc. Problem is, these are also hard
to find. Since I have my own business, I was able to get one at a chemical
supply house using my tax ID number. They won't sell them to the general public
because they think you're going to synthesize cocaine or something. You may be
able to check your standard science catalogs, or maybe McMaster's or Grainger's.
If you're not having any luck, and you still want to do this, let me know and
I'll see about getting one for you.
To cc a head, you cut a piece of clear plexiglass large enough to cover the
combustion chamber. Drill a 1/4 inch hole in it off to one side. Make sure the
valves and the spark plug are installed in the chamber you're going to measure.
Sounds obvious until you're wondering why the alcohol is running down the side
of the bench...
Put a THIN coat of grease all around the combustion chamber. Press the
plexiglass plate over the combustion chamber, with the hole right along the edge
of the chamber. Tilt the head so that the hole is at the highest point. Be
careful not to get any grease into the chamber area, as this will effect your
measurement.
The rest is pretty straightforward. Suck a quantity of rubbing alcohol into the
pipette, note the level, let it drain into the chamber, note the level again,
subtract the difference to get the amount of alcohol added. Keep doing this
until the chamber is completely full. You may want to repeat this a few times
until you get good at it.
Once you have the volume of the chamber measured, you can figure out your
compression ratio (assuming you know the compressed height of your head gasket).
I don't remember the formula offhand, but if you need it, let me know and I'll
dig it up. I use a little shareware program to do it for me, so I can screw
around with different volumes and gasket thicknesses on the fly.
One other note: don't leave the alcohol in the chamber. Either rubbing alcohol
contains water, or the hygroscopic properties are pretty high. I had a nice
coating of rust on my spark plug and valves after leaving it sit for a few days.
Let me know what you find out about your old head. I'm wondering if the earlier
TR heads didn't have the chamfer.
David Rupert
75701.242@compuserve.com
1967 TR4A (rigid axle)
1980 TR7 convertible
Waterford, Michigan USA
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