09 Nov The 3.2 litre short-stroke 911 engine
The 3.2 litre short-stroke 911 engine
During this summer’s road trip through Europe the old girl used 12 litres of oil driving 5,200 kilometres. Clearly I needed a new engine.
The 2.7 litre engine in my car had given up. It was leaky, used way too much oil and got too hot above 4,000 rpm. I suspected broken piston rings, defect valves and at least a bearing or two that needed replacement. But engine work on the 2.7 litre is hugely expensive because of the crank case modifications that need to done on the magnesium case, if you want to do a proper job. Which I did.
So I began searching auction sites and used parts dealership throughout the world for a good replacement engine. I had my sights set on either a 3.0 or a 3.2, both of which have a reputation for being solid high-performance engines with plenty of leeway for a bit of tuning.
Much to my surprise it turned out it’s a lot harder to source a good replacement engine than I would have imagined. Good 3.0 and 3.2 engines have become much rarer and more expensive than even 2 or 3 years ago, when my 911 obsession began.
Just as I was beginning to give up I got a call from Kim Clausen, the owner of one of Denmark’s most renowned garages: Porsche Centrum. He had just gotten hold of a promising engine. It turned out to be a late-model European 3.0 – the 930/10 model that was produced between 1981 and 1983.
This latest evolution of the 3.0 was also the most powerful of the lot, producing 203 bhp at 5,900 rpm and 267 nm at 4,300 rpm. So it was a huge step up from the 165 hp in the old 2.7 and the 180 hp in the earlier 3.0s.
But my luck didn’t end there. Years ago Kim had bought a 98 mm Mahle piston and cylinder set. They fit right in on the 3.0 case and upgrade displacement to 3.2 litres. The increase in power may not be that great – in fact it’s just 6,7 % or short of 14 bhp – but it transforms the whole nature of the engine.
If you’re used to driving a 2.7 litre 911 then the switch to a 3.0 can be a bit of a disappointment. It just doesn’t rev as willingly. So even though the car may be slightly more powerful, it simply feels a bit sluggish. The 3.0 to 3.2 upgrade does away with that. Since the stroke of the engine remains the same, while the bore increases, the power acting on the piston increases as well. That leads to an engine that will rev happily and quick. Or, in other words, an engine which is a lot more fun.
So, to cut a long story short, throughout this winter, magic will be happening in Kim’s garage, where he renovates the 930/10 and rebuilds it to a 3.2 short-stroke.
We have taken the decision to slap on my existing DANSK exhaust, which should be good for another 10 bhp, leading to a total of 225-230 bhp. With sharper cams that number could probably increase to 240 or so, but I wanted to stick with the CIS injection and the original camshafts for now. While I might sacrifice a bit of high-end power, I will get much better driveability. 270 break horse-powers don’t do you much good, if you can’t pull away from a Citröen Berlingo at an inner-city street light …