I am picking up a guni pig use for my PC tests. It is a 300SD engine so it is the uprated engine with the star chambered pistons and not ideal IMO for the slot mod.

First I will get it mechanically sound and instrumented up to get a good base line. Then I will start turning up the pump until I have reached the drivability threshold ( EGT & Smoke). With this less than ideal fueling set up, any pros and cons of any PC mod should be very easy to notice, basically better or worse EGTs with less or more power, nailing, and smoke.

With the star pistons I will start by just enlarging the burn holes in an effort to keep fire directed away from the vertical piston surfaces. MB increased the burn holes and saw a power increase so this should do something without putting the engine at that much risk. I would rater not cook a piston if I don't have to. If the EGTs go down and nailing is not an issue I will get new base line for another series of PC mods. If the EGTs go up, it is nailing, or smoking like crazy, and the problems can not be addressed with timing alone, than we have a good idea that this is not a good mod. If everything looks good I will turn up the pump again and so on to find a line. I am thinking that the stock turbo will be a limiting factor if the engine responds well the mod.

I am also thinking about putting a reflective coating on the inside of the PC ( except on the atomizing ball) to help reduce the thermal transfer to the head and cooling system. With the ball not coated it would remain hot and be able to cool itself via the chamber to head. Coating the out side of the PC would be easer, but the PC would not be able to transfer heat to the head and I am thinking it could melt down like a valve that dose not get enough seat time or when the lash is too tight and it doesn’t seat tightly. It will be tough to get the coating on with the ball in place. I looks like the newer PC balls are a rod type that is pressed in and supported at both ends. It might be able to be removed for the coating process and pressed back in after.

Again, any constructive thoughts?