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Old 11-22-2014, 09:23 AM   #5
Dwight Southerland
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Join Date: Dec 2001
Location: Arkansas - In the middle of everything.
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Default Re: Checking Total Cylinder volume

A lot of tech stories . . . Yeah!

Adger pointed out a couple of fine points of the tech process that you need to know. Once you start measuring stuff yourself, you will soon see that all those details of procedure will make a difference in the data. The fact that the .001"-.002" boundary layer oil film can make a difference in stroke measurement or that piston rock in the cylinder due to rotation around the pin will make a difference in deck clearance or that head gaskets do not compress evenly. Also, some procedures are applicable to some measurements and not others. (You can average the thickness of a head gasket but not the deck height or bore or stroke.) The detail of the procedures that have been developed over the years are to get accurate measurements and not allow for either the tech person or the builder-owner to fudge. If you are doing the engine building for yourself, it is always good to get a mind set to allow some cushion in specs so that you do not put yourself in a possible situation where you would fail a tech inspection. There are enough variables in a teardown event that fretting over that last couple of thousandths or cc's are not worth it. Even if you use precise measuring instruments regularly, getting repeatable measurements exactly is a challenge. The old rule books had a paragraph with instructions encouraging racers to allow at least .002" on critical measurements and .3cc on volume measurements. That's good advice.

Of course, you can always gamble the odds that you won't be torn down . . .
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