340 Static Compression Numbers and Test Procedure

nm9stheham said
Well that is pretty close. I have 719 grams for the stock 340 piston alone, plus the pin is another 154 grams, and I suspect the TRW pin+piston are about the same.

So if the stock rods were used, then the bobweight will be the same or close to stock. If the stock cast crank was used, then it ought to be close to the factory balance tolerance..... which was rather loose compared to what hot-rodders allow, but obviously it will survive.

So IMHO, time to carefully check over the TC for weights. Take pix. 92b's pix of the Magnum flexplate is a good illustration of weight sizes. It has the big weight on one side for the intentional external imbalance, and then a couple of smaller weights for fine-tuning it in. A neutral balance TC may have small ones so don't let those fool you. The 340 external weight will not be as large as the 360/5.9L external weight.

BTW, is it possible to fit your camera probe up into the oil pan drain hole and get pix of the crank and rods? IDK if you have a flexible probe or what....

Thanks again nm9! Ok so if I understand your thinking the rotating mass might be close to the original mass indicating that it might be running ( a 1973 set up) a cast crank which was externally balanced. This is my hunch too but means the HB was totally wrong as I had suspected not only the timing mark in the wrong place which was obvious but it was set up for an internally balanced set up. Also the Torque Converter balance needs to be confirmed through visual inspection.

Correct me if I am wrong here.

Now you brought up a great idea my bore scope IS flexible AND thin and should easily snake up through the oil drain plug! What a great idea. I might be able to find a parting line to capture on the counter weight.