performance tuning  & capacity upgrades

As we are able to supply and fit Silsleeve liners, we are also able to modify the bore sizes to a range of capacities. Even non-standard Porsche sizes can be catered for, but custom cylinder-head gaskets would almost certainly be needed.


Note that while most engines can be significantly increased in capacity, it's not always cost-effective. For example, it's possible to build a 3.9-litre from a 3.4 by additionally fitting the 3.6 crankshaft and bearing cradle, but it would be much cheaper either to start with a 3.6 or simply take the 3.4 out to 3.7 litres.

'We've done a lot of work on mixing and matching bore sizes and crankshaft strokes,' says Chris North (Autofarm Engine Builder). 'Almost anything's possible, especially if you went as far as changing the crank. You could even make a 3.9-litre engine from a 3.4, but we concluded that as far as the 986 Boxster is concerned the most realistic and cost-effective increases are to push the 2.5 out to 2.8, the 2.7 to 3.0 litres and the 3.2 out as far as 3.7!'

'You have to remember that the 2.5 and 2.7 share the same unique crankcase castings, and in the case of the 2.5, it has a particularly short-stroke crank.'

The 3.2-litre Boxster 'S' shares the same crankcase and heads as the 3.4-litre 996, hence as with the 3.4 litre 996, this can be taken right up to 3.7 litres.

The 1998-2001 996 3.4 litre engines (the ones which seem to have shown the most failures) can be taken out to 3.7 litres.

Power graph for a 996 3.7 conversion with exhaust and cams

The 2002-2004 996 of 3.6 litres has both a different crankcase and cylinder heads to the earlier 3.4, as well as a different crank and will bore out to 3.9 litres.

Also, mechanically the 987-model Boxster, Boxster S and the 997 Carrera are much the same construction as the last of the first-generation cars from 2004, hence the same engineering logic applies.

Cayman Rolling Road Figures - 3.7 with cams, induction & exhaust

And of course, even if you don't have a damaged engine to re-build and just want more power, all these options are still available to you.

Check out the capacity increases available below. Also, if more performance is what your after, why not check out the other performance options in our Performance section.

Model Type Capacity Increase Available 

 986 Boxster 2.5


 986 Boxster 2.7


 986 Boxster S 3.2

 3.7 or 3.9 with crank change

 996 Carrera 3.4

 3.7 or 3.9 with crank change

 996 Carrera 3.6


 996 GT3 3.6


 987 Boxster 2.7


 987 Boxster S 3.4

 3.7 or 3.9 with crank change

 987 Cayman 2.7


 987 Cayman S 3.4

 3.7 or 3.9 with crank change

 997 Carrera 3.6