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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sat Feb 08, 2025 10:10 pm
by rhd racer
I then started on the manifolds. This was always going to be a journey into the unknown - 996 manifolds use a stubby aluminium spacer that houses the injectors, whereas both 2.5 and 2.7 ones are all plastic. Another issue for the 986 conversion is that whilst the plastic part of the 996 one is less tall than the 986 part, when combined the 996 manifold height is about an inch taller overall. Most people use spacers and drop the engine and box but mine is so low (esp with slicks) I don’t want to do this if I can help it. I will need to see how it all works when it is in situ
This pic shows the height difference

The AOS pipe needs to thread through the manifold stubby (well I was guessing a bit because have not run these before but was proved right)
Next the left bank with no access issues for the back bolt this time, so I could finally fix the AOS
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sat Feb 08, 2025 10:15 pm
by rhd racer
The AOS can then be secured to the clips on the inside of the stubby manifolds
Next is the loom. You will see nothing is labelled! Basically I don’t tho k you can go too far wrong if you start at a given point and are methodical. In this case I used the mounting bolt I prepared earlier and bolted the loom in on that corner, and then you work forwards from there; alternator, knock sensor, throttle body, knock sensor, oil fill level etc etc
The coil packs and injectors are really easy as the lo runs rear to front so these just run in order and you cannot go wrong
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sat Feb 08, 2025 10:22 pm
by rhd racer
I then remembered that the crank position sensor at the back of the engine had a sheared bolt so needed swapping. Whilst trying to lever off, the sensor fell apart and left the sensor embedded in the case!

After a lot of heat I managed to knock the remaining bits out - I haven’t drilled out the bolt yet but at least this old crap is out. It was properly in there

.
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sat Feb 08, 2025 10:36 pm
by rhd racer
Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sat Feb 08, 2025 10:37 pm
by rhd racer
So I need to replace drill out the crank position sensor bolt, fit the plugs and coil packs, fit the new injectors I have treated it to and work out what combination of fuel rails to use - the latter poses an interesting problem
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 8:30 am
by sladey
Sheesh! Lot of work there!
Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 8:47 am
by misteralz
Really interesting thread this. I also don't bother labelling looms nowadays - poka yoke design principles on most post '80s stuff means you're just wasting your time.
Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 8:58 am
by rhd racer
Thanks gents - that was all done yesterday at medium pace. Rest day today…
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 9:42 am
by Gary71
Wonderful stuff, not exactly a plug and play conversion is it!
Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 5:44 pm
by rhd racer
It’s not Gary - partly fitting the engine in the reverse direction and partly that 2.5, 2.7/3.2 and 996 heads are all different so require matched inlet manifolds.
Should be worth it though. Last season the car had 189bhp per tonne versus 191 per tonne for a standard 986S. Pretty good.
However it will have 270bhp per tonne! I am in no doubt that it will require learning a totally different driving style to keeping it pinned everywhere. I think at some venues it will be instantly faster, but others (like Loton) I am not so sure. Will be a riot to drive regardless
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 5:54 pm
by rhd racer
For reference a GT3 series 1 is 262bhp per tonne, albeit has the advantage of higher torque and rev range
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 09, 2025 6:35 pm
by 911hillclimber
Needs a LOT of patience that lot Wayne!
Will be a real Hot Rod when done, fabulous.
The Lola is 571 bhp / tonne....
But I would rather go fast in a Boxster.
Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Mon Feb 10, 2025 3:40 pm
by neilbardsley
Looks of work. Well done
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 16, 2025 3:39 pm
by rhd racer
A slightly frustrating few evenings on the car this week. Firstly, in the Dempsey book it showed the throttle body reversed to allow for a really short AOS pipe. Mine has to run underneath the TB and back in itself, so I thought it seemed like a good idea
As you can see I have already taken one half of the plastic intake manifold off in readiness for this master plan - unfortunately it didn’t quite work out as the TB is not symmetrical
Apologies for the terrible pic - my phone camera was broken and waiting a part to repair. I couldn’t turn the TB with the crossover pipe because that would cause problems with the throttle cable. When I read back about turning it round the Dempsey book stated it was the fly by wire one, so the direction did not matter. Doh
Anyhow - what is an hour wasted when things were going to get worse - much worse
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Re: Slightly O/T - 996 rebuild / Boxster transplant
Posted: Sun Feb 16, 2025 3:50 pm
by rhd racer
So I had resisted messing with the crank position sensor as long as I could. I was enjoying buildings stuff and making every step forward look like just that, instead of a boring and tricky job that no-one would see. But, whilst waiting for some parts to arrive I thought I had best crack on with it.
The brief was simple - drill out the m6 bolt that had sheared, pop in my 2.7 sensor and bolt up. Easy.
Wrong.
The first issue was not being able to get the drill straight in the centre punched stud remains. The engine being built means that the back of the heads are in the way, and my 90 degree drill adaptor and my drill on a wire attachment could not get me on it straight either. The stub of the remaining stud would not come out with molies after heat either. So, a slightly wonky hole it is.
By slightly wonky I mean only a couple of degrees off square, and being a bit particular I thought it a good idea to put a timesert in it because the thread would not be perfect. This proved my downfall, as having made a7.2mm hole and carefully tapping it out to accept the 6mm timesert the tap snapped in the block. No amount of hammering would get the remains out, there was no exposed end to twist it out, and it is too small to try and wind out with circlip pliers or similar.
Rats
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