Quote:
Originally Posted by JSLRacing
P-G a motor?
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A P&G gauge is like an air pump gauge graduated usually 1 to 100 in 1/4 increments like a CC tube or more depending the range of the guage. . You screw in a fitting into the spark plug hole of one cylinder. After making the rocker arms of that cylinder inoperatable so both valves stay closed you spin the engine with the starter with the fitting connected to the P&G by a hose. The reading you get on the "pump" from a puck sliding up a glass cylinder gives you XX as a reading. Add a % of factor for the temp of that cylinder measured with a thermometer and listed on a chart supplied with the P&G gauge. Then you mutiply times the number of cylinders 4,6, or 8 to get the cubic inches. They usually measure 1 to 3 cubic inches UNDER the true size of an engine IF done correctly unless it spins to fast because of a16 volt starter systems. If the figure is OVER the claimed cubic inches then either you did something wrong or its time to pull the head and physically measure the engine. Thats about as good as I can explain it on this forum. Its eaiser to use and show someone how to do it than explain it here. A P&G is not "dead on" tool but a good indication if someone is cheating or not on the size of the engine claimed. The inspector should always make sure the fitting used is the one supplied as Ive had guys try to slip by by changing fittings with a "Bleed hole" in a fitting they have and THAT would give you a false reading. I wont mention names here but I can tell you it was usually a Pro stock racer from the good ole days....LOL and it was tried at an NMCA race years ago by a well know 409 Chev. engine builder. Ya gotta keep an eye on everyone.....LOL.