Block size

[klaitun]

In researching putting a larger engine in my 944, I've found 3 different sizes that have been used. 2.5 litre being the most common and only that I've seen through 1988. In 1988 it seems they started using a 2.8 litre in the turbo models and around 1990 they had a 3 litre in the 944 S2. I'm wanting to bore and stroke an engine to a fairly large size... Are these three engines all the same block or different? I looks like to me that the 2.5 and 2.8 are different blocks, but the 3 litre is just a bored 2.8. If this is the case, I'd like to get a 2.8 and stroke and bore it myself. Correct me if I'm wrong about any or all of this.

[Steve Taylor]

I recall reading that these engines are made of aluminium and the pistons run in an etched silicon layer or something - bottom line is - no rebores. Steve

[fletch]

The 2.5L engine was used in all early 944s including turbos. This displacement was achieved with 100mm pistons and a 78.9mm stroke. In 1989, Porsche produced a 2.7L engine for the 944 and 944S using the same 78.9mm stroke and 104mm pistons. Also starting 1989, they produced a 3.0L engine which was used in the 944S2 and the 968 using a crankshaft with an 87.8mm stroke and the 104mm pistons. Porsche also produced a 3.0L Turbo for the 968, but only about a dozen of those were ever made. Some companies have marketed stroker kits for the 944 (most commonly used in the 944 Turbo) which uses the 87.8mm stroke crankshaft and 100mm pistons for a displacement of 2.8L. However, this also requires using a piston with a different wrist pin location (for valve clearance) and either different connecting rods or block machining. The 944 cylinder walls are aluminum lapped with a silicon compound which precludes honing in the same fashion as a steel cylinder. However, the factory shop manual details the process for honing the cylinders and relapping the cylinder walls with the compound.