911T modifications

[Kirklands 904]

Some years ago I bought 911T engine 00203-700 in a serious of cardboard boxes. It appears to be all there except for the alternator/fan and housing but includes the Webers.

I am starting to think of the next project and would like to rebuild this engine to give around 150/160 HP at a reasonable cost.

Can I ask for suggestions from the wealth of knowledge out there as to what parts I should start looking for?

[haasad]

Cheapest is to build it with a bit more compression (new pistons), match the exiting inlet perfectly head to manifold, maybe 32/34 mm chokes in the existing carbs (rejetted). S spec or similiar cams decent headers at 1 5/8. Build it carefully with good attention to fit and clearance special care on valve to piston. Run a decent ignition trigger and ignition source. It would come close to 150hp methinks.

[impmad2000]

I run a bog standard 2.2T, but with throttle bodies, distributor-less ignition and EFI I get a very nice 156 bhp (Measured on Bob's rollers).

[jonat127]

Cheapest is to build it with a bit more compression (new pistons),

I am in almost identical situation and was wondering the same. So, when you say high compression pistons are these just pistons from a 2.4S or are they something different/special?

Would there be any advantage over the std 2.4T to just fitting the hi comp pistons and venturis and jetting the carbs but sticking with the T cam?

[911hillclimber]

I think Andy is correct, and I would suggest a good read of the Bruce Anderson tuning book would help, full of combinations that work.

You are effectively building an E or S engine without the mech injection.

Those engines rev to a much higher red line than the T which will pile in the BHP.

[fetuhoe]

Your engine number doesn't really work as it should start 208XXXX and if it is a 2.0 litre it will be a 901/03 Type.

These engines produced 110 BHP at 4200rpm and do need a little detailed work to bring up the power.

The heads have the same valve sizes and the 911S but much smaller ports and I would think about opening these out.

The cranks are non-counterweighted and there is some debate about their fatigue life at high revs but for a Road engine they should be OK.

Compression was 8.6:1 and needs to be raised with better pistons. (Woessner?)

The Cylinders are Cast Iron rather than Biral and I don't like them for engines with increased power output as they can distort with the increased heat developed.

The Ignition advance curve is also likely to be incorrect for something like an S cam and this will need to be dealt with.

The S engine ran 32mm venturis in the carbs and these would be a good starting point.

I would also worry about 2 other areas of this engine.

The 1967 911T was the first 911 engine to use investment cast rocker arms.

These original cast rockers did not have any bushes and ran directly onto the rocker shaft. They have a bad habit of galling and picking up on the shaft. They need to examined carefully and probably replaced.

If the tensioners, tensioner arms and chain ramps have never been replaced they would also benefit from an upgrade as the parts used in this era of the engine were not noted for their reliability.

I would have thought 1 5/8" headers a bit on the big side for a 2.0 litre and a 1.5" should be adequate.

Cheapest is to build it with a bit more compression (new pistons),

I am in almost identical situation and was wondering the same. So, when you say high compression pistons are these just pistons from a 2.4S or are they something different/special?

Would there be any advantage over the std 2.4T to just fitting the hi comp pistons and venturis and jetting the carbs but sticking with the T cam?

The 2.4 S piston is, of course, incompatible with a 2.0 cylinder head as the valve angles differ and the combustion chamber is much shallower.

At 84mm diameter it would not be feasible to bore an 80mm diameter cylinder.

You cannot easily fit a 2.0 head onto a 2.4 barrel as the end preparation and sealing arrangement is incompatible without significant work.

You also need to be careful abut 84mm diameter high compression pistons.

If you have a 2.4T the compression ratio was only 7.5:1 and the S increased to 8.5:1 which isn't really much of a change.

The 2.2S also had an 84mm dia piston but the compression ratio was 9.8:1 and these pistons are a much better upgrade.

If you run a High Compression piston with a very 'soft cam' such as a T cam you are likely to encounter serious pinking and if you increase the compression you really need change the cam duration as well.

If you have Zenith 40TIN Carbs on the 2.4T they will need work when the engine is modified - we have used them on 3.0 engines with more than 250BHP with good success and have a range of parts to make them relatively easy to tune.

[Kirklands 904]

Thanks for the advice and suggestions.

I suffered from finger trouble in my original email, the engine number is 208 - 0700 and 2000cc so is a 901/03 type as has been pointed out.