2.0 engine upgrade
 

I have a 1975 Porsche 914 with a 2.0L engine and I would like to but bigger pistons in the motor but I have two to choose from either the 103mm or the 104mm. My question is what is the different besides 1mm and besides head work what else do I need to do.
Thanks

You need to do almost everything. The heads need to be cut to fit the cylinders, they need a lot of work to flow enough air for the large cylinders, the case needs some work to fit them, and you need a cam to complement the very different heads you will wind up with to support the large cylinders.

Chances are pretty decent that you'll need to have the cylinders trued up and made the same height and made round and the ends squared off; the quality with them isn't as good as it could be. And the heat dissipation isn't great, so they'll likely wear out relatively quickly.

Oh, and you have carbs that are big enough to support the displacement already, right?

In general, there are fewer problems with the 96mm cylinders. They fit in 2.0 (and 1.8) heads and last better than the really large-bore ones. Combine that with added stroke and you can get about 2.2 liters and have a fun motor. Jake Raby makes 2270cc motors that are putting out over 150 HP on the dyno, which is quite respectable in a 2100 lb car.

--DD

Thanks for the info but does is matter if I go with the 103 or the 104 pistions

The wall of 103's is already thin. 104's will just be more sensitive to overheating and warpage.
The stock '75-76 exhaust is the most restrictive of all the model years. Do you have an exhaust system that will handle the additional flow, and reduce the likelihood of overheating?

Yes, go with the 96's unless you have EXTENSIVE experience with engines. You cannot "bolt on" >96's without a redesign of just about every other engine component.

Last engine I built was a Raby kit 2316cc used 96mm pistons and 80mm crank. Enough power to wax a Mustang GT on the race track. 210 HP 195 ft/lbs. That will get it done.
Ran cool and made 26 to 28 MPG cruising @ 80 MPH.

How much did that cost you?

914 engine upgrade
 

is this a raby built engine?