Slightly O/T - 996 rebuild / Boxster transplant

[rhd racer]

You might have seen the odd photo elsewhere of the 996 engine project I have started. I know there is growing appreciation for the early Boxster 986 (now 27 years old!) so hopefully there are some interesting bits and bobs here for a few of you.

A bit of history first as to how we arrived here. I have been hillclimbing for 22 years now, in a 911 2.2E, 914/4 2.4 then converted to 914/6 3.0 CIS, then onto carbs, Boxster 2.5 later converted to 2.7. Basically 22 years of pinned throttle everywhere, not a single car above 220bhp. It’s time to play with the big boys and learn some new skills.

The car is a 1997 Boxster 2.5 shell. These are the lightest Boxster at 1250kg and hence my starting point, and it has been self built since 2013. Initially a Cat C bought from Copart, I used the bits from a cut and shut banana donor car and had a repaired and road legal Boxster for just £2,500. Since then it has been developed bit by bit and now is about as developed as it could possibly be. As it stands now it is 1150kgs, despite having added 50kg of cage and safety equipment. Not bad and there is a bit more to go.




Running on slicks it is quite a weapon, and has been known to beat GT3s and 4s up a hill. In 2022, my friend of 35 years Angus Archer of AMS Porsche built me a 2.7 engine which on paper gained me 7hp over my tuned and mapped 2.5, but it gave me loads of torque and crucially another 1k revs and I won the Porsche Club Speed and Hillclimb Championship outright. In 2024, I was a very close runner up to Steve Jory’s fabulous 944, in one of the closest finishes ever decided on countback. So with that, I decided to do something new and put the car up for sale


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[rhd racer]

Whilst looking for a new base car (I was thinking of a Cayman S), I stumbled across a 996 3.4 engine for money that was too good to be true. I sent the vendor two messages (it was a salvage co), and he confirmed that it was a 71k mile car, with no smoke or rattles. I bought it for about 20% of what it was worth, and right enough it was there when I went to collect it.

We decided to strip it as an insurance policy and frankly, apart from replacing the exhaust studs and replacing a cam sensor which has been cut off, theoretically it could have run quite happily. There was no bearing wear, the only things we found to be wrong on initial stop down were the nylon chain guides were badly worn and mostly in the sump. When we put it back together, this was found to be caused by a collapsed tensioner which we replaced. The heads, known to crack and worth £1500 each in the condition mine were in, were perfect. These went off to be skipped so they were perfect, and have new guides and seats for the valves, plus the aforementioned exhaust studs re tapped.

The shells showed no pick up and even wear, unusually in these engines the crank sits in its own carrier, rather than directly to the case, as seen below.




The bores were perfect in the undamaged liners. Even the RMS (an early single row and therefore a bit more reliable) showed no signs of damage or leaking and I was asked if I wanted to re-use. I didn’t.


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[rhd racer]

A few weeks ago I arrived at Gus’ workshop about 10ish on a Saturday morning for the build. It is a couple of hours from me, and I had picked up my bro-in-law en route from a railway station as he was collecting his 997 after a service. Suffice to say, I was too late to see the crank go together in its carrier - Gus had made an early start. Obviously all new bearing shells were used and the crank had not needed grinding- still being in tolerance



All the other shiny bits on the bench were mine mad ready to go




You will not that one bank of pistons are already on the rods - more of that later



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[rhd racer]

So I decided to go for a ceramic IMS upgrade after going to all this effort



The origin one was entirely serviceable though - by pure luck.




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[rhd racer]

First step is to fit the intermediate shaft and bearing, before adding the chains to the end of the crank, and drop the carrier into one of the case halves



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In the 2nd photo you can see a factory tool tensioning the chain so it doesn’t fall off the sprockets. We replaced the chains too


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[rhd racer]

So at this stage, the pistons that were assembled to the crank are already in the bores on one bank. Essentially with the case open you can get to the rod end bolts and do them up in situ. When the case halves go together, things get a bit more funky



The sealant is the stuff that goes off when there is no air, so forms a seal pretty quickly on contact.



So what you are looking at here is a long piece of nylon which you feed through a blank in the case past two cylinders and onto the last in the bank to hold the conrod.

With the crank locked, you tap in the piston down the bore and withdraw the nylon tool. You then take another tool (similar to the nylon one, but this time steel) with the fudge on pin on the end and feed it all the way through to secure the piston. Then the moment most are nervous about, you withdraw the tool and fit a clip on the end, feed it all the way through the two unbuilt cylinders to the last in the bank and with a good strike of a hammer, knock in the clip. A torch and mirror inspection later and you know it is secure. Angus checks what he already knows by the sound it makes. You can imagine that the clip getting slightly snagged at this point means it will likely ping off somewhere in the assembled block, and the whole lot needs to be separated and cleaned / reassembled again! This jeopardy continues on the next two cylinders, after a quick rotation of the engine to get the piston in the right place, albeit the distances of feeding through are greatly reduced




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[rhd racer]

We are know ready for heads, so following head gaskets they go on and then my deep baffled sump. This holds an extra litre or so of oil and has big baffles like an X50 optioned sump.




.


I had taken this off my 2.7 in advance, and put a standard sump plate on what is now my ‘reserve engine’


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[rhd racer]

Then cam followers



And then cams (2 per bank, 4 overall, 24 valves variocam)



Sadly I didn’t get any pics of the cam timing but it is quite unlike an early 911. Essentially Gus sets the cams in their seats at an approximate or base setting by virtue of the chain. At the other end there is a factory tool with two aluminium guides which simply align two slots in the end of the cams- they are then bolted down whilst aligned by the tool. That is that. No gauges!

Here is the collapsed varioram tensioner. We managed to pop it out, however it is badly scored so we replaced it




And above the damage on the nylon guides


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[rhd racer]

And then loaded it into the Abarth (the most hilarious daily I have ever had) which is amazingly versatile as these engines are pretty heavy old lumps



And ready for swap from 996 to 986 configuration (if you think about it, there are numerous things which are on the wrong side of the engine based upon the configuration in reverse). More of that next time if anyone is still awake / interested!!




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[stretch]

Very interested. Did you consider doing any of the Hartech upgrades whilst in there. ?

[hot66]

Love this

[rhd racer]

Very interested. Did you consider doing any of the Hartech upgrades whilst in there. ?

I didn’t to be honest. A couple of reasons;

1. I really lucked out with the engine I bought so it didn’t need new liners to make it work
2. Whilst my class is limitless for power by virtue of the 3.4 (I could have 300hp or 500) there are limits to the drivetrain. Boxster S run 260hp through a 6 speed box, whereas 2.5/2.7 derivatives use a 5 speed box (of which I have two, both with Kaaz plate LSDs. The box is perfect for hills with the slightly longer ratios meaning less gear changes, though it has to be said the ultimate power capability is somewhat untested. Basically, with modded exhaust, inlet and mapping I hope to have 310-320bhp paired with a gearbox designed for 220…..
3. With a car already almost 10% lighter than an S, and almost 20% more power than an S and no driver aids, I think it is going to be interesting to drive!!!


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[rhd racer]

Both gearboxes incidentally are modded for 2003/4 only output shafts, which allow the use of a single model year driveshaft which is 25% bigger than a standard shaft


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[rhd racer]

Love this

Cheers James


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[PeterK]

Good stuff