Piston popup

I see, thanks. when I did my engine jc specialties sold the crank bearings,seals,arc rod, and a wiesco piston, to work with the flathead crank and you had to cut the top of the piston yourself which was good because then you can set your own pop up in the block, depending on the thickness of the head gasket to achieve a 0.030/0.035 quench.
 
JC sells the pistons now with the top of the piston cut and the under side relieved for the rod. you can also get a stock piston with no machine work done.
 
It's next to impossible to get the pop up right with out assembling the engine and measuring the pop up before the piston is cut.
The stroke may vary a couple of thousandths as well as where the top of the piston is in relation to the wrist pin.
The deck height may also vary slightly from one engine to another.
I measure every one i build before i cut the piston.
Yes i have uncut pistons.
 
When measuring stroke and using a caliper remember to subtract the "in the hole" distance for stroke. Had a tech man try to toss me because he didn't take that into consideration and said I must be running a stroker motor.
 
With regard to detecting detonation, more years ago than I care to remember I had the good fortune to run into a Champion Spark Plug rep who traveled to major races all around the country assisting Champion users. His name was Bobby Ralman/Rahlman - not sure of the spelling, but he could tell an awful lot about what was going in your engine by using an illuminated magnifier to look ALL the way down the center electrode of the plug, clear to the base, as well as the rest of the area exposed to combustion. He looked at my plugs and said we were on the ragged edge and needed to back off our timing a little, because there were signs of incipient detonation. The signs, clearly visible on the center electrode when he showed me what to look for, were minute flecks of aluminum on the center electrode. The aluminum flecks came from the top of the piston, peeled off by the beginnings of what could become serious detonation without remedial action. When you don't have serious vibration measuring equipment, this actually works pretty well. Years later I put 20 miles on a backyard turbocharged engine in a street sleeper and saw the same thing - that one was cured with the installation of water injection before the pistons were damaged any noticeable amount; in that particular series of engines, the upper ring land (the metal between the piston top and the upper ring groove would totally disappear in a very few thousand miles due to this incipient detonation, which seemed to occur at boost pressures over 10 psi; more serious detonation can destroy an engine in a couple of minutes or (a lot) less.
 
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