964 3.6 cylinders in 911 SC 3.0

[Peter1027]

Hello!

I am interested in converting my 3.0 SC to 3.6 964 cylinders to achieve 3.3 l displacement. As far as I have read I need to widen the stud bores in the cylinders and change the diameter of the cylinder base as well as changing the conrod bore.
My question is: is it possible to reduce the diameter of the 964 cylinder base as much to be able to install the cylinders without opening up the block?
Does somebody have the diameters of the 964/SC cylinder base?
Further, is it possible to use the 911 SC heads without changes?

Thank you!

Greetings from Austria,
Peter

[Henry Schmidt]

I've done it many times and it's a longer conversation than you might get here.
Short answer, not worth the effort.

[LukasM]

Originally Posted by Henry Schmidt

I've done it many times and it's a longer conversation than you might get here.
Short answer, not worth the effort.

Listen to Henry Peter, he has been doing this for a while...


From what I understand 98mm is the biggest bore you can achieve on a standard 3.0 or 3.2 case, while retaining sufficient wall thickness so the cast Mahle/Kolbenschmidt cylinders don't get oval very fast, and the spigots get too thin (1,5mm wall thickness at the thickest parts....) . This is why you shouldn't bore out a 95mm Mahle/KS cylinder more than 98mm.

If you want a 100mm bore you normally machine the case to fit the 105mm spigots. LN Engineering does offer a 100mm billet "Nickies" cylinder that is a slip fit into the 103mm stock case bore, but I don't know how longevity is on these. Even being billet, I doubt it will be as good as a 2,5mm wall thickness cylinder. Additionally, these cost around $3000 more than a 98mm piston + cylinder kit.

Those are probably the reasons why the 3.2 SS is so popular, and very few people build a 3.0 into a 3.3 or 3.2 into a 3.5 engine.

Liebe Grüße aus Wien,
Lukas

[mepstein]

I was thinking exactly what Henry said. Displacement is great for more power but that’s not the only way to get there. We put a Peter Dawe built engine in one of our customers cars. It’s a 3.6 but doesn’t feel like any 3.6 I’ve ever driven. It’s strong at low rpm’s. At 4k, it feels like a turbo has kicked in.
We just built a twin plug 3.4. You would never know it was once a stock Carrera engine. Starts pulling at 3k and has power through 7k. Again, feels like no Carrera engine I’ve driven. Unlike the Dawe engine, super linear power. With a custom short gear trans, it’s a hoot.
We do have a 3.55 liter Carrera engine with carbs. Hard engine to build. Long stroke crank. Wider than stock. It’s a ripper but not a beginner build.

[Peter1027]

Thank you all for your answers.
So you convinced me to keep away from the 964 cylinders.
Another option would be to open up the orginal cylinders to 98 mm. Does anyone have 98 mm pistons laying around for a reasonable price?

Thank you once again,
Peter

[Peter1027]

Another possibility: 930 cylinders with 97 mm.
Are any modifications needed? Is it possible to get compression ratio up?

[Henry Schmidt]

Originally Posted by Peter1027

Another possibility: 930 cylinders with 97 mm.
Are any modifications needed? Is it possible to get compression ratio up?

The 930, 97mm cylinders will fit and were in fact used in the 911SC-L 3.1 upgrade.
The Turbo cylinders had minimal finning, so cooling was/is compromised.
We manufacture a 97mm kit that replicates the SC-L kit but uses a full finned cylinders.

https://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/1163435-porsche-911sc-leistungsgesteigert-piston-cylinder-kit.html

Engine type 930.03 or 930.09 * 3.1 *
Engine displacement: 3122 cc
Bore x Stroke: 97mm x 70.4mm
Power: 210 hp @ 5900 rpm Binary: 280 Nm @ 4300 rpm
0 at 100 km / h: 6.4 seconds Max speed: 230 km / h

The Forgotten 911SC-L
Porsche's 1st factory tuning engine kit that was NOT in the option list for those years (Dealer Secret)
Rolf Sprenger, The Father of the Porsche MFI for the road cars and the Slant Nose 930
Designed this 3.1, 210hp Tuning kit for customers that were not happy with the output and performance of the normal 911SC 3.0 78-81
This tuning kit has a output of 210HP @5800 RPM and 206 Torque @ 4700rpm
Roth used 97mm 3.3 Turbo Cylinders with 9.5:1 compression Pistons made it 3122CC
3.1-L Engine Leistungsgesteigert or Increased Power
Bosch reworked the CIS injection with new Distributor
Taller 5th gear and larger oil cooler from the race department
3750.00 dollar Option in 1978
ONLY spread word of mouth at Porsche Dealers showroom
when customers voiced displeasure of the performance of a normal 911SC
Never was available in the USA only Europe and ROW and only a Letter from Rolf was included in the glove box with this upgrade
No way of knowing how many of these tuning kits were made
Some estimate 200-300 unit made
Roth Sprenger Personal notes and Porsche refusal to Market the SC-L
almost left no documentation to this special rare 911

[GG Allin]

My 3.2 based 3.6 uses 964 cylinders. The case and the cylinders were machined to fit each other. The motor previously ran a hard life and seems to have held up good. When I rebuilt it, I sent the cylinders to LN Eng. to be replated and honed to spec. None were rejected. The other thing that was done to them back in the day was modification to the stud spacing, seen below . It seems there are better ways to 3.6, but im very happy with mine. The other odd ball thing about this engine is the 5.25" Pauter rods. So maybe it's a little more relaxed when running hard.

[Peter1027]

Thank you for your reply!
Were you able to use the original cylinder heads?

[Henry Schmidt]

3.0, 3.2 and 3.3 heads will work as long as you use early 964 cylinders as shown in the illustration.
Late 964 cylinders will offer another set of challenges.