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[ltank]

   I am trying to understand why the TC cylinder spigots are short compared to S&S cylinder spigots and earlier Harley cylinders.
If I remember correctley the, piston skirts must be clearanced when the pistons are at BDC. This means that the cylinder spigots would come down almost to the flywheels too. The older cylinders were notched for clearance to the flywheels and where the front cylinder meets the rear cylinder at the peak of the 45 degree deck at the center case bolt. The bottom of the pistons skirts used to be at the bottom of the cylinder. With that being said,
    Now the TC case decks are at 6 inches and the stock TC cylinder spigots are shorter and dont even come close to the flywheels. S either the piston skirt comes down some below the skiirt into the motor case (Very Bad in my opinion) or the new pistons have musch shorter skirts that increases the chance of the piston Rocking causing excessive wear on piston and cylinder or is it due to the increased rod length from 7.44" to 7.667" ?

[HD Street Performance]

It may explain why the HD 113" with their Bigger Bore cylinders is such a good combination.
Cylinder support at BDC provides better piston stability which provides better ring seal, ring and cylinder life, and cooling.

[Ridgerunr]

Would S&S 4.125 cylinders and pistons along with S&S 4.125 stroke flywheel/rod assy fit factory cases?

[HD Street Performance]

Twin cam S&S cylinders are available in that bore but stock cases will need to be bored.

[HILLSIDECYCLE.COM]

S&S cylinder spigots are substancially longer than OEM.
When boring the cases for 4.125" bores, S&S dictates a 2-step bore process.
4.162" ID, X 2.250" depth, then 4.322" ID X 1.545" deep.
And once upon a time, when they offered the also very powerful 116" kit, those had 4" bores.
Those were 4.075" X 2.250", then 4.255" X 1.550".
Scott