2.0 w 2.4 P&C what do I have?
 

My engine was built in eighties by Franz Blam. He used the original 2.0 case and added 2.4 cylinders and I was told the pistons were from an S. Running Webers. Can anyone tell me what this configuration is? I was told by someone it creates a 2.5 SS? Thanks

You need to know what the stroke is. 2.2 and 2.4 engines both use 84mm pistons, so if you have the stock 66mm 2.0L crank, you have a 2.2L motor. If you have a 2.4 70.4mm crank, you have a 2.4L.
If you have the 70.4mm 2.4L crank, I think you would need an 87mm Piston to achieve 2.5L.
Bob B

The 2.5 short stroke configuration uses the 66 mm crank and 90 mm pistons and cylinders.

Well I guess it will remain a mystery unless I can talk with Franz and he remembers. It was a long time a go, so I'm not holding my breath. I will say he knows how to build a leak free case. I have two of his builds, one in each of my cars and both were built in the mid 80's, and both are dry at the case. Thanks for the help.

You need to know what crankshaft you have. 2.4 pistons from an S on a 2.2 crank wont give you much of a compression number.
Bruce

2.0 and 2.2 both use 66mm crank. (2.4L is a bit of a fib, as the engine is only 2,341cc, less than 2.35L)
Please correct me if I am wrong, but I am guessing that the 2.2 and 2.4 pistons are different. The 2.4 pistons probably have the pin closer to the crown to compensate for the longer stroke? For that reason, you can't use 2.4 pistons on a 66mm crank, because the piston won't come high enough into the chamber to give you any useful compression.
Bob B

Porsche raced two "2.5" liter motors. I think the first used the 70.4mm crank, but they had problems. So went to a larger bore and the 66mm. Easy to check using common references like Frere or Anderson. The 2.3 of the ST used 66mm cranks and 85mm pistons.

2.5 Racing Motors
 

Checking my 911 "bible", Bruce Anderson's book, lists the following:

Type #911/70 from 1971 was 86.7x70.4 for 2492 w/ 10.3:1 CR for 270@8000 RPM w/ Mechanical Injection

Type #911/73 from 1972, also w/ MFI, 89x66 = 2466, same CR, 275@8000RPM

Does not say whether these were S cammed or 906 cams.

Hope this helps,
John