2.2T - 2.3S/T engine

Please excuse my header as I have not posted much here before, so apologies if I have missed the same / similar thread elsewhere on this forum. I was not able to find such when using the search bar above. I should point out, i've not built a 911 engine before, so i'm not coming from a position of great knowledge here (aside from reading Paul Frere's 911 Story, and Bruce Anderson's book).

I have a '71T that I want to warm up from 49yr old stock configuration. Car was delivered new with S Calipers, Koni suspension, and 5 speed, so a warmer engine I feel might be a nice touch. I should point out, the car will be running F/R 16mm anti sway bars, and CR6ZZ tyres on 6X15 flat Fuchs. Having said this, I'd like to stay as original as I can, without getting silly. I did speak to one learned Porsche mechanic in the US, who's engine advise was; 1) bore 84 steel jugs to 85mm, 2) retain unbalanced 66mm crank, as under 2.4 it can handle more revs (he said ~9000), and 3) move to S cams. Other mentions were; porting, stronger valve springs, Ti spring retainers, lighter Carillo rods (ok, he said Ti ~450g/ rod), and re-jetted 40IDA 3C/1, which I have.

In a nutshell, this configuration was suggested as being able generate ~220hp.

Just wondering if this configuration makes sense for a fast(er) street motor, without going all out?

Any thoughts / comments / suggestions are most welcome.

Ok. I will bite. There are lots of short stroke packages that work great for what you are trying to do. Your crank will be fine. Surf around on the Bird for piston and cylinder combinations that work and last. The most preferred will likely be some Mahle/JE 2.5 combination. I would shoot for a compression ratio of around 9.5. Don’t touch 10 unless you are going twin plug.

That said, no 911 motor is going to turn 9k for long. Think 7500-7800 max with as much area as possible under the curve. Port with this in mind. My hunch is you will be pretty close to S spec. Forget all the TI. It doesn’t belong on a street motor and will have zero discernible advantage. A nice set of 2.0 or 2.2 (heavier) rods with updated bolts will be fine. I would not use S cams on such a smaller motor or one w lower compression. E, solex or better yet a more modern DC design. These will be all-in well under 7800. While less peak HP it will actually BE faster everywhere but on a race track. Use the springs for that go with the cam. Factory will be fine.

Quote:

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Originally Posted by geneulm

Ok. I will bite. There are lots of short stroke packages that work great for what you are trying to do. Your crank will be fine. Surf around on the Bird for piston and cylinder combinations that work and last. The most preferred will likely be some Mahle/JE 2.5 combination. I would shoot for a compression ratio of around 9.5. Don’t touch 10 unless you are going twin plug.

That said, no 911 motor is going to turn 9k for long. Think 7500-7800 max with as much area as possible under the curve. Port with this in mind. My hunch is you will be pretty close to S spec. Forget all the TI. It doesn’t belong on a street motor and will have zero discernible advantage. A nice set of 2.0 or 2.2 (heavier) rods with updated bolts will be fine. I would not use S cams on such a smaller motor or one w lower compression. E, solex or better yet a more modern DC design. These will be all-in well under 7800. While less peak HP it will actually BE faster everywhere but on a race track. Use the springs for that go with the cam. Factory will be fine.

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Wow, thanks Geneulm, that's a really helpful response. I did read about the Solex cams as a grind somewhere between the E and S, however what do you mean by a more modern 'DC Design'? Yep, agreed, all valid points re Ti ... I actually found many sets way lighter than standard, but not Ti, such as 550grams, still ~200 lighter than stock. Of course, lighter ally pistons make sense, and as you say, this is a very fast street motor. Chance of this car being on a track is extremely remote, so I think we've covered most of the bases here. Many thanks again. Adam.

Dougherty Racing Cams.

The factory cams work great but they are old designs. People have learned a lot about these since the mid/late 60s. Especially when picking a camshaft to fit a particular engine package. The GE series are also quite popular. Good luck.

post duplicated. No clue why?

Quote:

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Originally Posted by geneulm

Ok. I will bite. There are lots of short stroke packages that work great for what you are trying to do. Your crank will be fine. Surf around on the Bird for piston and cylinder combinations that work and last. The most preferred will likely be some Mahle/JE 2.5 combination. I would shoot for a compression ratio of around 9.5. Don’t touch 10 unless you are going twin plug.

That said, no 911 motor is going to turn 9k for long. Think 7500-7800 max with as much area as possible under the curve. Port with this in mind. My hunch is you will be pretty close to S spec. Forget all the TI. It doesn’t belong on a street motor and will have zero discernible advantage. A nice set of 2.0 or 2.2 (heavier) rods with updated bolts will be fine. I would not use S cams on such a smaller motor or one w lower compression. E, solex or better yet a more modern DC design. These will be all-in well under 7800. While less peak HP it will actually BE faster everywhere but on a race track. Use the springs for that go with the cam. Factory will be fine.

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This is great advice. You won't win any pixxing contest but you'll have great driver for twisty roads while retaining tractability.

The only other things I would 'consider' are uprated oil pump, later chain tensioners, front mounted oil cooler and case upgrades like shuffle pins and ARP type case bolts.

Cheers,
Mark

FYI. There is a gentleman on Pelican who is selling a set of mahle
86.7 pistons and cylinders. These were designed to make a 2.5, 10.3:1 long stroke factory racing motor. However with your 66mm crank it would be a 2.3, with compression in the mid/high 9s depending on spec of your heads. All has been checked out by pretty reputable folks: Aaron Burnham/Henry Schmidt.

Pretty cheap for a nice setup. No skin in the game