Big Jugs, No, not THOSE jugs... :/ Options

[tumamilhem]

Please forgive my mechanical ignorance, but what exactly are "jugs" on the engine? When you put larger jugs on an engine for more power, exactly what does that mean and by how much power does it increase?

[Dave_Darling]

"Jugs" is a nickname for the cylinders.

I think I have heard of 107mm cylinders at one point. The largest common size is 105mm. They're a whole lot of work to fit, and they require significant machining of the case and heads to even fit at all. Let alone work to flow enough air to adequately fill the cylinders. And work to make sure it stays together for a little while.

The general consensus is if you go larger than 96mm cylinders, you either spend the big $$ for the Nikasil-plated aluminum cylinders, or you live with the idea that you'll be rebuilding very frequently. The big cast-iron cylinders don't seem to be made that well, and they don't shed heat as well as aluminum does.

The cast-iron 96mm cylinders can work pretty well. With the stock 1.7 or 1.8 crank (66mm stroke), they give you 1911cc displacement. With the 2.0 crank (71mm) you get 2056cc.

--DD