Posted by Wietse on December 13, 2001 at 15:09:46:
In Reply to: learning about engines, 101, 3.5liter vs 2.8liter posted by Adam Wilson on December 13, 2001 at 13:25:27:
The external dimensions are exactly the same between all M30 the engines. Here is what I know:
The 2.8, 3.0, 3.3L all have water jackets that go all the way around the cylinders because of the smaller bore, the 3.4/5L do not, the cylinders liners are connected between bore centers. The 3.3 can be bored to a 3.5 without issue because the Germans are so conservative on their block design.
My block orginally had 89mm pistons and now sports 92.5mm pistons.
The connecting rod lengths are the same for all the engines and because of this the later long throw cranks (86mm) produce agressive connecting rod angles and this puts a good deal of side load on the pistons, this inturn causes later high mileage 3.2 and 3.4L to have greater bore wear than earlier short throw crank engines.
The 2.8 and 3.0 share the same crank (80mm). The 3.2L and 3.4L share the same crank (86mm). The M block or early euro only 3.5 have a different crank (84mm). The way you get different cranks in the same block without changing the deck height (distance between the centerline of the crank and the top of the block) is vary the location of the wrist pin height in the piston.
Even if all the versions of the M30 had the same diameter pistons, the wrist pin height is different to accomodate the different crank length throws. Because of this you can not build a 3.6L using a 86mm crank, big euro factory pistons 93.4mm and stock connecting rods, the pistons would travel to far up in the bore, making contact with the head.
Hope that helps.
Wietse