I am looking for a head with PCs to use as a mock-up for porting, a new cam, and PC mods for my 616 turbo research project over the winter. I saw one for a 616 in the parts section & sent a PM but no dice so far. I think a 617 would work as well for what I want to do with it. If anyone knows of a junk or really cheep one that would help with my research. Some old pistons dished pistons would be helpful as well extra cams to mock up.

I am going to cut a slot accost the three burn holes that point towards the center of the cylinder and parallel to the head & piston. The slot will start at the right and cut accost to the left. This will direct the fire horizontally over the piston and head.

For this set up I would prefer to use the new uprated type 2 PC in combination with a standard power type 1 dish piston. I will need to machine the piston for the longer PC and make the valve pockets deeper for a new cam. With the modified PC the star chambered pistons that are required with type 2 PCs would see fire directly on the piston star groove walls, ( can't think of a good way to describe it) where the dish would be open.

Depending on what I can get for parts, and a donor engine, I could start with a standard power engine and cut the PCs to get an idea of the difference. The flat bottom of the type 1 PC is not as strong as the type 2 PC but the slot should reduce the pressure in the PC, ( less restriction ) that is where some of the power would come from. MB increased the hole Dia to get more power so the slot would flow even more. My thought is that the thicker bottom of the type 2 PC would handle heat better and it appears that the PC ball is supported on both ends.

My thinking is that getting enough fresh air into the cylinder is not the problem although the cam is not the best. I think the problem is getting enough fresh air in to the PC and the rapidly expanding gasses out with minimal resistance. I think the " over fueling" and associated rapid and high EGTs are from the PC loading up during full power. They can't get the gasses out, there is very little time to get fresh air in and fuel builds up in the PC. I think that is why 617s need to run so much boost for so little increase compared to DI engines. If the slot will allow more air into the PC faster and the " over fueled" gasses to get out of the PC and into the combustion chamber faster so they can use the air in the combustion chamber that currently is not taken advantage of before the piston has traveled too far. This would be as close to a DI as we could get and still have the PC benefits.