diameter of combustion chamber of a 3.2L head?

[gliding_serpent]

AS my engine is nearing finishing of assembly, I was reading a great old post on deck height by Grady Clay. He had some great diagrams, and I am now trying to visualize the shape of the air pocket generated between my 3.2 heads (unmachined aside from valve re-seat), and and new 98mm pistons (Max Moritz 3.4L, 9.8:1).

My engine is assembled, so no pulling out the ruler.

Using the below image as a guide, what is the diameter of the head combustion chamber at it's widest point? is it 95mm like the stock 3.2L pistons?


My 98 mm pistons. note that the dome rise is offset from the edges. Presumably to make up for what I am guessing to be a 95mm head diameter.


Thanks for any help.

[Tie Rod]

If this helps, a quick dial measurement on my heads was a 94.8-ish mm Inside measurement is hard to get right at the edge on both sides and at exact widest part. Seems reasonable to call them 95mm. Also, mine were turned ever so lightly, so they may be a tad smaller.

[KTL]

Mahle purposely shapes the piston with a "shelf" at the outer diameter to compensate for the smaller diameter combustion chamber. But thinking logically, it makes good sense to blend the combustion chamber to smooth that transition from the larger piston OD to the smaller combustion chamber diameter.

Keep in mind this will affect your combustion chamber volume. If I recall correctly, my twin plugged head volume with the chamfer for 98mm pistons, along with NGK BPR7ES upper plugs (14mm thread size) and DCPR7E lower plugs (12mm thread size) resulted in a 91.1cc dome volume. The commonly published dome volume is 90cc.

[gliding_serpent]

Thanks for the info guys. For sure on the smoothing. Grady mentioned that.

I was trying to sift through the masses of internet dogma that using the solder method does not measure deck height. With my 98mm pistons, it does when you visualize the overhang/lip from the 95mm opening to the head. My deck height was a touch over 1mm.