Bill,
As shown on the dyno graph, the 9m 993 +3 engine is currently tuned to peak power of over 350hp at just over 6500rpm but is still making good power at 7000, hence the bottom end is primarily being upgraded with the new rods as a future proofing exercise to allow safe over-revs to 7500.

Future proofing is the secondary consequence of the rebuild, with the Motec M600 already installed a 400hp upgrade with 9m race cams & 9m ITB system would be a straightforward step up, as shown on another customer's 993 graph. Incidentally this 400hp 9m Clubsport race engine package is running with standard 993 Bischoff heat exchangers, cat bypasses and stock silencers.

Thanks Colin,

I was curious about the rod change w/o using the GT3 pump and GT3 crank & possibly GT3 rods

I love reading about your projects!

Looking good Colin...

Couple of questions on your engine rebuild:

Do you install the RMS dry?
I notice there is no sealant on the engine case with the crank installed, do you put the sealant on the other half then mate together?

Bill,
My first race engine was a 993RS motor on stock crank, Carillo rods, 9m 103mm P&C set with 9m Billet heads and ITB set up. On stock headers that engine ran for three seasons, making 425-435hp on our dyno. The peak power was 7300rpm and I took the engine to 7800 without an issue. For the last season I increased the rpm limit to 8000rpm and on stripdown deduced that I was on the edge of oil flow at the big ends. For this reason I consider the stock crank to be good for 7800rpm but no more.

Obviously with the GT3 bottom end the engine could be spun much higher (given suitable rods & pistons) but we have to look at the cost to performance benefit of such a change given the limited budget already in place. IF (and it's a big if) the customer had the necessary funds and IF he was 100% committed to running ITB and race cams and IF he wanted an 8000+rpm limit, I agree that this would probably be the optimum choice.

Mark has covered the crankshaft with clear grease to fit the RMS.

As suspected, Loctite 574 sealant is applied to the top half of the case only as it is a lot easier to fit the crank into the dry half and clean off any oil residue with brake cleaner than it is to re-apply the sealant and wipe it off the lubricated crank.

Perfect, Thanks Colin.

Colin, love the detailed photo's of your builds, gives me food for thought.

In the lower photo of your post #77, the welding is very close to one of the glued in cover plates for the many round body shell dipping holes, would I be right is saying these are steel and not plastic?

Yea, those plugs on the floor of the unibody are metal, not plastic.

Hi Colin,

a little off topic question:

what kind of 993 engine would you build for a street car /DD car (half city / half road-highway use)? What would be the estimated HP, torque?

thanks for your answer

Arpad

The key choice to tuning an aircooled 911 engine is the RPM limit which will is the main limit the hp that you can achieve. For a 993 street engine running below a 7000 rpm limit with the stock intake (non-VR or VR) and exhaust system, a 9m billet head/sports cam/remap combination will see 340-350hp on a 3.6 engine or 350-360 on a 3.75 litre engine. This is the basic specification of the engine above and is pretty much the limit to what can be achieved with conventional tuning.

That said, we're now working on an unconventional performance solution which might, if things go to plan, re-write what is thought possible from a roadgoing aircooled engine.

Well then, please keep us in the loop if said plan comes to fruition.

:bowdown:

:corn:

The following morning Mark had the crankcases together so now the engine is ready for the pistons & cylinders. I'm going to be machining the pistons to change the compression slightly, once that is done the motor will soon come together.

Welding complete, underbody is prepared for painting.

We will be using a conventional etch prime, primer, base coat & laquer process, so no corners cut even where you can't see it.

Airbag delete panel and cage cross brace now welded into dash.