Originally Posted by frog
mmmm, not sure I do get it....
Would that be because the head isn't actually flat in that area, again, helping to concentrate the fuel mixture as close to the plug tip as possible ? A decompression plate would raise the head, but in a straight up direction, therefore not reproducing the slope in the head's combustion area ?
The decomp plate will increase the space between the top of the piston and the squish area in the cylinder head, in the 1st pic, they are very close together:
Adding a decomp plate now makes them further apart, so not "squishing" the mixture as much as it should do:
**this is my understanding of what has been said in this post**