3.5 turbo; seeking input on pistons and cylinders

[JKav]

Engine is a 3.5L (3.2 case bored to 105 mm), twin plug, turbo. Heads, ancillaries, case and related bottom end bits are all sorted and in hand. Looking for input on pistons and cylinders, which I need to source.

Pistons - this is a 91 octane build, so thinking 8:1 CR. 2618 probably a must. That means… CP (preferably in their X-forging) or JE (preferably in their FSR forging). Any others?

Is there a “mature” CP/JE/other piston out there that fits the above bill? Considering that my engine recipe is pretty mature/sussed-out by now, I’d rather avoid roll-my-own custom unicorn pistons.

Cyls – are Capricorn cylinders suited to 2618 pistons, thermal expansion-wise? Certainly the LNE cyls are, though they're pricier.

Trying to keep this build pragmatic, so pretend you’re spending your own money here in the responses.

[Ollies930]

Why not go with Capricorn pistons? That way you do not have to try to figure out what clearance you need.

[Henry Schmidt]

Originally Posted by JKav

Engine is a 3.5L (3.2 case bored to 105 mm), twin plug, turbo. Heads, ancillaries, case and related bottom end bits are all sorted and in hand. Looking for input on pistons and cylinders, which I need to source.

Pistons - this is a 91 octane build, so thinking 8:1 CR. 2618 probably a must. That means… CP (preferably in their X-forging) or JE (preferably in their FSR forging). Any others?

Is there a “mature” CP/JE/other piston out there that fits the above bill? Considering that my engine recipe is pretty mature/sussed-out by now, I’d rather avoid roll-my-own custom unicorn pistons.

Cyls – are Capricorn cylinders suited to 2618 pistons, thermal expansion-wise? Certainly the LNE cyls are, though they're pricier.

Trying to keep this build pragmatic, so pretend you’re spending your own money here in the responses.

100 mm 3.5 cylinders are a challenge but if you want a great set of 100mm pistons for a 3.5 turbo build you can easily modify any 964 pistons.We might even have a set of good used pistons (turbo or NA) on the shelf.
We've been doing it for years.

[JKav]

Originally Posted by Henry Schmidt

100 mm 3.5 cylinders are a challenge but if you want a great set of 100mm pistons for a 3.5 turbo build you can easily modify any 964 pistons.We might even have a set of good used pistons (turbo or NA) on the shelf.
We've been doing it for years.

Thank you, Henry. That's the kind of resourcefulness I can get behind. However it was my understanding that the 964 100mm piston has 1mm shorter compression height than the 3.2 (or 100mm 3.5) piston so I'd looked elsewhere. Is this not actually the case, or ?

[Henry Schmidt]

The additional deck is a minor issue issue. Compression is easily maintained. If the additional deck clearance bothers you, offset the small end rod bushing. The benefits just keep multiplying. Better rod length to stroke ratio being a major one.
You can also grind the rod journal to fit a 3.0 rod. Benefits multiply there as well. Rod length to stroke ratio plus 10mm bolts. This smaller rod journal was used almost exclusively in Porsche racing engines including the high RPM Gt3.