Ok, I won't have time to respond much in the morning, so I'll give the low down on this lowly 318 tonight.
The first time it was built, it was bored +.030" with a stock replacement cast piston. It was not torque plate honed and the rotating assembly was not balanced. For a stock rebuild, it should have been ok, but it lacked power.
The second shop insisted it needed more compression, so they swapped the stock replacement cast pistons for KB hypereutectic flat tops. Again, not plate honed, and not balanced (even though he said he was billed for balancing). This is a problem because the KBs don't weigh the same as a stocker, but it's not a huge difference, like a forged TRW slug. However, it smoked and leaked oil pretty badly. The customer never mentioned any vibration, but when I asked about it, he did say it droned at highway speeds.
The reason I asked the questions in my original post, is so I could make these points.
1. If you don't plate hone, you will never know how far the cylinders will distort when assembled. In this case, (are you ready for this?) number four cylinder distorted almost a full .006" at approximately the top of the second ring travel. That has to be the worst I've ever seen, although the 40% leak down on that cylinder told me something was terribly wrong. A couple others were in the 30s. I still hear guys say a small block mopar doesn't distort much because the bolts are so far from the bores. Baloney! Apparently, these two engine builders didn't feel it was important to plate hone a 318. I had to hone the block to +.040" to get it straight and round within .0002", and get yet another new set of pistons.
2. If you don't have the rotating assembly balanced, you won't know if it is out of balance, or how far. In the first build, the builder could be forgiven for making the assumption that a running stock engine, rebuilt with stock weight replacement pistons, could forego balancing. But, he would be WRONG! The second shop was derelict in his profession by using aftermarket pistons, charging for balancing (according to the customer), and not doing it.
When weight matching the connecting rods, they were 46 grams different from the heaviest to the lightest, and that was on the SMALL (pin) end. I had to replace the heaviest rod because there wasn't enough balance pad to grind away to make it light enough. The big end was only 19 grams difference from heaviest to lightest. Still, that's a far cry from a finish weight difference of 2 grams or less. Once all the components were balanced, I removed 90 grams from each end of the crankshaft to get it within spec. This is proof that even the factory components can be so far off that you can't risk not having the assembly balanced if you want it to live a long and happy life. In stock form, this engine had to be a shaky turd.
It's amazing what some shops will let go out the door, and I'm encouraged by the responses here of people who want to do things right. But wait, there's more! But, that's another engine for another thread.
