Slightly O/T - 996 rebuild / Boxster transplant

[KS]

Interesting stuff! I have to say that I found myself fascinated by the modular construction of these engines when I saw one apart at Williams Crawford - Harry their engine man explained about the gudgeon pin deal. That's clever!

[impmad2000]

Harry their engine man explained about the gudgeon pin deal. That's clever!

Blew my mind too. How nuts is that !!

[911hillclimber]

Great to see and read about Wayne.
So rare to see this design built-up.
Love the cam timing! If only an air cooled engine could be set so simply.

I presume the induction will be stock as a starting point?

Bit down the line, maybe you have decided already: What clutch will you use?

[rhd racer]

All will be revealed Graham! I am a little behind - I expect to have it in and ready to fire by the end of the weekend so next instalment to follow later


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[911hillclimber]

Teasing us now, but nothing to what you be when the season starts to a few others!

[rhd racer]

So a bit of a catch up to the present day

I won’t bother covering engine removal as there are loads of guides for that. There are a few ways to do it - gearbox first, then engine it together as a unit. I prefer the latter, but it is a heavy old unit so a jack on the engine and the box is required, and a low trolley.

The biggest challenge by far is safely getting the car high enough to pull the unit out. I will try and post a pic to explain when it goes back in, but the unit is wider than the subframes for the lower suspension mountings which the gearbox sits between, and they are also the lowest point of the car. In essence the bottom of the rear bumper needs to be about waist height to be in the ballpark. My scissor lift is no good for this, so slightly sketchy use of two jacks is the order of the day.

This was I think my 5th complete removal spamming 3 early 986s I have owned now, plus at least 5 gearbox swaps on top of that. So I tested myself and did it all from memory, only forgetting the power steering return line. Not bad, and no damage done. There are lots of connections s though, some really tricky and in tight spots, and they are expensive to replace so it does take some patience. Disconnecting the loom from the ECU and feeding g it through the bulkhead onto the engine always makes me chuckle, but there are about 300 wires so a connection for would not work.

I explained in another thread to Graham that I did the hard bit when transplanting the 2.7 into the 2.5 chassis. The reason for this is a 2.5 has a single pipe on the inlet manifold with a single resonance flap, whereas the 2.7 onwards all have two pipes and two flaps. These massively increase the torque. In fact, I drive the new engine on a track day to run it in last time at Donington with the 2nd flap cable tied open and it was as slow as….

Wayne Schofield pasted some code from a 996 into my 2.5 ECU so it recognised the 2nd flap, and via a small solenoid and some vacuum pipes the difference was totally unbelievable. The pics should illustrate - first the 2.5 from my old Tiptronic



And the 2.7 in my car from the first build



A slight complication with this conversion is having to use the 2.5 throttle body on the 2.7 manifolds, because it needs to retain the cable set up (everything after 99 I think was fly by wire). This makes things very tight on the rear bulkhead and for code air feed supply.

Therefore, theoretically all this is taken care of and paved the way for the 3.4. Theoretically


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[rhd racer]

Before we get to that, we need to convert a rear facing engine to front facing format.

The 996 is held on a mounting bar much like a 911, where a 986 has a single central mount like a factory 914/6. The former is mounted via studs, the latter by bolts so the studs need to come out



Next up is gearbox removal. Fairly straightforward although a little more effort that a beetle or a 914 with 4 bolts! I removed the two lowest (a small hex bolt and a hex nut) whilst in the car, as you cannot reach them easily when in the deck. Then it is simply a case of removing the rest.

The best advice I can offer is to get a piece of card and mark out the bolts like a clock face / this will save you hours of head scratching g trying g to work out which goes where





As an aside Tiptronic gearboxes are right funky things to remove, involving I think an 8.5mm drill bit to lock the torque converter (in the absence of the factory tool)…now that is an odd process.

Anyhow, a quick lever off exposes my lightweight flywheel(I ditched the dual mass several years ago)

And then pull the clutch off.




You can see I use a paddle clutch which is pretty ferocious, but is said to help the harmonics of the crank when a solid flywheel is used. I understand they have been known to crack cranks. You can see that standing starts in slicks have taken some life out of the clutch plate, but it is probably only 1,000 miles old so will go again.

I will reuse all this set up as it should be more than enough to cope with the 3.4.


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[rhd racer]

You can see here the two IMS bearings - first the ceramic upgrade



Then the factory early single row one we used on the 2.7. These were the most reliable stock bearings and as you can see it is bone dry, if not a little scarred by clutch dust



I then swapped over the flywheel, using my faithful VW locking tool (one ear snapped off) which has been in service for 35 years



The after an initial torque you then do a final torque of 120 degrees. The bolts are supposed to be single use, but to be honest when you mess around with a race car as much as I do you need to reuse stuff to make it economical, so these will go again. I mark them so I don’t lose my way - I did a first fit then removed each bolt, used a drop or two of loctite then did the final torque.

I won’t fit the clutch yet, for reasons that will become apparent later


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[rhd racer]

Then moving to the front of the engine I started with the power pulley. This is a smaller pulley than standard, which again is supposed to help protect the crank from harmonic imbalance, and uses a different length drive belt to standard as a result. It has the added benefit of reducing load on the engine, and combined with a flywheel makes everything more responsive. The issue is that to fit it you need to cut a lug off the case - on the old



And then to illustrate the standard block







Then the low temp thermostat (reused as only 600 miles old)


And the water pump (same use). The inlets / outlets are in a different orientation to the 996. New metal gaskets containing sealant used throughout obviously



.






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[Ian Gunney]

Looking good Wayne.

[rhd racer]

Then more coolant housings and moving the water temp switch - the below showing a 996 vs 986 one



This one requiring the alternator bolt and idler wheel to be removed



And then the front engine mount. This being quite clever - it has two bottom bolts easily accessible under the car if you need to, and the top ones just require a half turn on a spanner to allow you to take the whole mount off by rotating it about 30 degrees




My front mount is already updated with black urethane bush

I then lifted the old engine onto its rear face (behind the flywheel) to remove the exhaust studs. This is another big weakness of these cars, they shear off and I spent a week drilling and tapping mine in my 2.5 engine using a special jig Angus leant me. Tedious work, so I was glad the machine shop took care of this on the 996 motor. From the factory they have bolts, but prefer studs to prevent this happening again. So I swapped the titanium studs from the 2.7 to the 3.4, and I will loctite some stainless ones into the 2.7.



The only issue was that 3 of them had time serts fitted and these came out too - so a carefully removed them I. The vice and ran a tap over them. I will loctite these back in the 2.7 when new high temp loctite supplies arrive



I already have some equal length headers in stock. I used these to help tease 213bhp from the 2.5, but couldn’t use them on the 2.7 because the standard engine achieved the bhp limit for the class




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[sladey]

Awesome stuff Wayne - thanks for sharing.

I think I saw that gudgeon pin thing on Matt Armstrongs GT3 engine build and assumed it was GT series trickery - had no idea that came in with the 996.

[rhd racer]

Cheers Ian - hope all is well

So this is how far I have got so far, apart from some induction planning which I will save for later.

The rest looks pretty daunting but is straightforward, though jeopardy increases with the risk of dropping something in the engine! The beauty of everything so far is that I haven’t had to unwrap it yet!







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[rhd racer]

No worries Mark

Got a bit lost with my photo ordering somewhere there but hope you kept up! Bony so easy doing such a photo heavy thread from my phone!


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[rhd racer]

Not so easy… see what I mean


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