3.8L build on a Carrera 930 case?

[Fly911]

I need advice for or against my plans to build a 3.8L (3746cc) on my 1987 Carrera 930 case. I have talked to various "experts", and got very diffeent answers. Here is an email I sent to LN Engineering:

I have a 1987 Carrera 3.2L that I’m turning into a track toy, primarily DE events. The car itself is ready for the track with 930 brakes, gutted interior, roll cage, coil over suspension etc, etc. I have been collecting engine parts over the last two years, and I will soon have to decide on pistons and cylinders.

I have been advised against 102mm P/C on a 930 case, both Rothsport and JB Racing tell me that the cylinder walls will be too thin and the case weakened to the point where it will be unstable and eventually leak, or even worse crack.

However, my mechanic Mike Callas (Rennsport, Sealy Tx) says that the 102mm on a 930 case is no problem. What experience does LN Engineering have on the 100mm vs the 102mm on a high revving 930 type engine?

The engine will be built with following mods:
• 997 GT3 crank (76.4mm), cross drilled, knife edged and balanced (purchased)
• 997 GT3 oil pump (purchased)
• 997 GT3 Pankl titanium rods (purchased)
• 959 intermediate shaft (purchased)
• Twin plug heads, ported with titanium big valves
• RSR (sprint) cams or DC100 cams or similar
• Jenvey 48mm individual throttle bodies
• Canems ECU and coil pack ignition (purchased and installed)
• High flow injectors (purchased)
• Light weight flywheel and clutch
• Fabspeed equal length headers and race exhaust (purchased and installed)
• Close ratio gear box w/LSD
• Etc, etc…
The engine will be built to endure 8,000rpm+.

Please advice.

Here is the answer I got bck from LNE:

Thanks for your email. We've been making machine in 102s since 2004 with zero failures or complaints. We did however change the case register to a 106.50, which is slightly smaller than the original Mahle kit which required the 107mm case register. The cylinder skirts themselves are plenty thick and will not have any issue. In fact, we make slip fit 100s which are much thinner and many have used them in race duty as well. Mike is a great engine builder and knows his stuff - I would not hesitate going with whatever recommendation he makes. Ultimately, it's your engine builder you have to trust.

Additionally, you probably will want to upgrade to the FSR forgings which allow for the pistons to be lighter and stronger, especially since you have so many other upgrades with the purpose of reducing reciprocating mass.

If you have any further questions, please feel free to let me know.

Charles Navarro
LN Engineering | 626 N. Locust St. | PO Box 401 | Momence, IL 60954 USA | Phone: 815-472-2939 Fax: 413-280-9041
LN Engineering Nickies The Original and Genuine CNC Billet Aluminum NSC-Plated Cylinders


So all you "experts" out there, what is your opinion on this?
I look forward to some well funded advice!

[nikke911]

I´m planning a similar build and would also be interrested in comments from the experts.So lifting this thread in case someone missed it..

[akuraina9]

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