So, I'm gathering up parts for my 408. My buddy gave me a set of very slightly used Diamond pistons that he used in his stroker build. The guy who built it apparently wasn't familiar with LS engines. He built it with 5 left side pistons and 3 right side pistons. He had oil problems, took it apart and saw the mess. Now, thinking i just needed to order 1 piston from Diamond, upon closer inspection, the number 8 piston had some machine work done to it. The area under the pin had been clearanced on one side and you can see a crack. Is this necessary on the 408 stroker build? I'm not even sure if it came from Diamond like this or if the machine shop/builder did it. Every piston has 2 numbers on it. 11519 on all 8. 7 of them have the number 18643 but the machined one has 17962 on it. Does anyone know if the number 8 piston in the 408 stroker build needs to be different?

 

The number 8 was sometimes has to be machined to clear the reluctor wheel on the back of the crank, but it sounds kinda like the reluctor clearanced the piston itself. Most pistons use a narrower pin boss and shorter pins so it isn't necessary to do that anymore.

 

Bingo! Just got off the phone with Diamond. Number 8 is clearanced for the reluctor wheel. Looks like the builder took it a little further.