Posted by Frank on Tuesday, December 11, 2001 at 9:29AM :
In Reply to: Re: how to measure cylinder head volume posted by keithbarrett on Tuesday, December 11, 2001 at 0:16AM :
I used to do this when I worked in the Experimental Assembly department at General Motors. We did it exectly the way described, but we used what we called "lifter leakdown fluid" instead of water. We used to do tests on hydraulic lifters, to see how fast they leak under pressure, and we needed to pump them full of fluid before doing those tests. This fluid was very viscous, smelly, and seemed to be some kind of a cross between diesel fuel and kerosene. I am not sure of the composition of it though. In any event, the engineers always insisted that we measure cylinder head volume with the lifter leakdown fluid. Apparently, this fluid doesn't bubble up as much and gets into smaller spaces than water does. But for a low compression engine like in a Powerwagon, I can't imagine how it would make that much difference what fluid you used.
We also had what we called a "whistle" machine for checking head volume. We had calibration bottles and inserted a probe that emits compressed air into spark plug holes. Some sensor in it picked up the frequency of the resulting sound. It works on the same prinicple as blowing across the top of a glass bottle, different sized bottles will give you a different sound. This was a relatively expensive machine, but I would imagine that shops that do a lot of high-performance engine work might have one. This machine could also be used to get the volume of the combustion chamber at TDC for each cylinder, and could be programmed to directly read out compression ratio for each cylinder (then average the cylinders for the entire engine). But, this machine was very sensitive to dirt and oil (hence, could only be used on new engines before they were run) and also sensitive to environmental changes (temperature, barometric pressure, etc.).
I sold my 1968 WM300 Powerwagon in 1984 and want another one real bad now.
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