944 Turbo S Engine Rebuild Thread

[Eldavo]

Now I "think” I’ve worked out how to post photos I’ll start populating a thread charting my Turbo engine rebuild.

No point arguing about what’s been done or "why didn’t you do xyz” as it’s done, all back together and going back in the car next week.

For the the avoidance of doubt, its a Turbo engine not a N/A engine - the thread‘s about that so i’ll keep it on that topic and I’ll happily answer questions about it too.

So, rewind back to October last year and my May statement of "I’ll have the head removed by June” had been proven to be false. Cam tower was off, inlet manifold, belt covers, fuel rail and plenty of ancillaries but life got in the way and the car was sat half stripped in the garage:

I had at least got around to fitting the new seats that I’d had for erm . . . a year:

A chat with my friendly Indy’s where they were ribbing me for still not having got round to it I finally went enough is enough and arranged to have it trailered to them:

Should have done it ages ago as it took them no time at all to strip it down and then get it out:

Elvis has left the building:

Cross member, etc. bolted back in place and another trip on Steve’s trailer and Felipe was back home in body but not in spirit!

Now to to get that engine stripped!

 

[Eldavo]

Well, that’s borked.

 

[Eldavo]

While speaking to a few people in the UK who were undertaking rebuilds about what options I had next I decided to treat myself to some shiny bits and do a few little jobs I’d been putting off.

Picked up a TTV Flywheel - this has a 60-2 missing tooth trigger wheel machined into it so will let me run a single reference sensor with my ECU and feed it a decent signal rather than using the gnarly starter ring:

Replaced the cracked and damaged climate control plastics with a strengthened 3D printed one:

Tidied up the charge pipes with some paint, lacquer and a fresh sticker (repainted a wall in the utility room too hence the tin of paint):

New hatch pins fitted:

And I really should do something with the rest of the wiring loom now I’ve made the passenger compartmen side all good again:

These injector plugs have definitely seen better days:

Weighed up my options and decided that rather than sleeve the block at this stage I wanted to retain the Alusil bores, my block was too far gone for anything other than sleeving so I put the block and head to one side for a rainy day and got a late N/A block and head. I considered a 2.85 stroker or 3.0 Turbo build but decided that an OEM+ approach fitted my ethos and notional budget - I will probably get the original block sleeved at some point for a 2.85 build or collect the remaining parts for a 3.0 depending upon time and life commitments in the future.

The late N/A block is identical and the upper balance shaft cover even has a blanking plug instead of the Turbo oil feed banjo so easy peasy. Loads cheaper than Turbo blocks too - I bought one with a light score in one cylinder, it would need rehoning anyway and an overbore added minimal cost. The N/A head has a higher flow rate as well as no ceramic port liners to potentially cause future issues so all the bits went off to AMAC Engineering "down the road” in Northallerton. They are one of the few places with the correct Sunnen stones and polishes to bring out the Alusil surface after boring and honing, and had a 944 Turbo race engine in at the same time for a sleeved and deck plated build so knew what they were doing. A set of ARP head studs had magically arrived from the States too so they went along for the ride.

A 4 series Gran Coupe has a remarkably practical boot; for those that don’t know, its the 5 door hatchback version of the 2 door coupe version of the 3 series 4 door saloon - obviously.

 

[AndrewCS]

[s5] ... thank you, looking forward to the remainder of the journey []

 

[blade7]

Wonder if the damage was caused localised heat, related to ignition scatter from the trigger issue?

 

[944Turbo]

Excellent, Nice looking car
Tony

 

[Eldavo]

A bit of cleaning and measuring, a skim of the head and block deck to minimum RA50 and an overbore from 100mm to 100.5mm left me here ready for the Alusil process:

A "during”:

And all done:

Had the N/A head rebuilt with all the Turbo valves, new seals, etc. and had it drilled and tapped for the Steam Vent Mod at the same time:

100.5mm bores need 100.5mm pistons so these turned up:

 

[Diver944]

Excellent thread, keep it up [][][]

 

[Eldavo]

It was fair to say that the clutch (not original) had seen better days:

I got a new clutch and while I was at it, picked up some Oilite bushings to replace the crappy needle roller bearings on the clutch fork pin and also had the clutch fork welded back up and filed into profile again as the tips were very worn. Only half the tips contact the bearing so a fair old groove gets worn in them - Turbo clutch forks were NLA for years and are available again but at £470 IIRC I went for repair rather than replace!

New clutch, new flywheel, etc. so got the rotational assembly balanced, as individual components and all together, marked up for reassembly. Interesting to note that at 170k+ miles the crank was only just below the upper new measurement and was so hard that it took a fair bit of elbow grease to file the areas back to balance it. They don’t make them like they used to:

Had it all polished and whatnot too - while you’re in there and all that:

 

[Waylander]

thats getting pretty close to porn on the forum,

they did a nice job on the block.....

 

[Eldavo]

I did consider other options . . .

 

[Eldavo]

With the engine out it was an opportunity to give things a bit of a clean up and think about a few options for the future.

The previous owner had had removed the air con pipes in a somewhat rudimentary fashion:

As you can only fit the pipes with the engine put I figured now was a good time to replace them. I’m planning a few road trips and another ‘Ring trip with the car so would like aircon back in spite of the weight penalty, etc. I got hold of a full set of lines, condenser, compressor and mount, new seals, receiver dryer etc and set about refitting them as well as painting a few brackets, replacing some bolts, etc. There is an aircon pipe retainer clip missing in the pics as I had to order an oil pump drive sleeve from Rose Passion and it was easier to add the clip to that order as I forgot to order it from my OPC:

It‘s important to remain comfortable and find a suitable place to contemplate life:

And what good is a cake without a few cherries on the top:

No need to thank me :

 

[Eldavo]

My bits from Ishihara Johnson in the states turned up, a Teflon crank scraper:

And an oil pickup support bracket:

Best crack on and start the boys on bolting bits together then!
Crank in, girdle on and start eyeballing the crank scraper for fit, the Teflon part should make very light contact with the crank so that it wears to be a perfect fit:

Everything getting torqued down to spec:

Gary trimming it to fit:

Looks good to me:

 

[Eldavo]

Now to order a head gasket, measured the wear tab on the head and then needed to add that to the piston protrusion on the block. To do that we needed pistons in. My ‘88 Turbo S had the Rarst forged rods from the factory, so these were checked and measured before getting the thumbs up and mating to my shiny new pistons:

Fitted them loose, gave them a wiggle around to find TDC and then measured the protrusion to get a HG thickness, went for a 0.053” over the factory 0.040” from Cometic. Ordered it off the shelf from Performance Unlimited in York late on Friday afternoon and it was in hand by Tuesday.

Using a a dial indicator on one of the head studs to find TDC to measure piston protrusion:

Did the maths for the ring gaps and they came in near as dammit bang in the middle of the suggested range, so measure twice, trim once and they’re good to go:

Definitely looking more engine-ey by the day:

 

[Eldavo]

Sump got a clean (and not just because I spilled a mug of tea in it) - you can’t see it under the tray but there’s a Lindsey one-way trapdoor welded in the bottom to stop oil starvation under high cornering loads:

Balance shaft housings on and a bit more assemblage:

The oil pan gasket is a PITA to deal with on a Turbo thanks to the crossover pipe, etc. so a good coating of elephant snot will keep it in place and leak free:

Best fit those ARP head studs and see what it looks like with the head in place:

 

[blade7]

I researched Alusil reconditioning a while back, and contacted Sunnen. Got the info on the correct roughing/finishing/polishing stones and the felt set. Plus the silicon compound and honing oil. I decided if I ever built an Alusil engine that I'd spec top clearance on the cylinders and the rings. Fingers crossed AMAC got it right, it would be good to add them to Serdi and Capricorn as a machine shop to use for Alusil.

 

[Eldavo]

Sometimes you just know by speaking to people that they’re the right ones for the job.

Proper old boy who had probably forgotten more than most knew - showed me around the work they were doing on some Honda drag engines, through to BMW and Porsche stuff. I’d researched the Sunnen process too but learnt more from talking to Alastair for 10 mins. Left most of the decisions in his hands, he decided on the overbore size, sourced the pistons and made sure they were right.

I pitched up with a Turbo Head, a N/A Head and a weblink of where to find the details to drill for the steam vent kit. He gave me back a bare Turbo head and a fully rebuilt N/A head with all the springs, valves, seals, etc. all done and ready to fit; along with paperwork for how much material had been removed from the head and deck and what rings had been specced along with recommended gaps.

Total cost for all the machine work including balancing the rotational assembly, building the head, etc. was about half what Serdi had quoted for sleeving the block. AMAC would've happily sleeved the block and made me a closed deck plate but given my intended usage it was decided to go for the factory cylinder finish - again, cost wasn’t really a factor although the numbers were significantly smaller than Serdi’s again.

 

[blade7]

Sometimes you just know by speaking to people that they’re the right ones for the job.

Proper old boy who had probably forgotten more than most knew - showed me around the work they were doing on some Honda drag engines, through to BMW and Porsche stuff. I’d researched the Sunnen process too but learnt more from talking to Alastair for 10 mins. Left most of the decisions in his hands, he decided on the overbore size, sourced the pistons and made sure they were right.

I agree, Alusil has been around for decades. And it's not black magic to expose the silicon crystals when someone knows what they're doing. No doubt there's more shops capable than the 3 mentioned in this thread, but some others I contacted didn't inspire much confidence. And I can understand why the likes of EMC and JMG have had ferrous liners fitted. I'd still favour Alusil if I ever build up my 104mm block, but mainly because I'd want to retain the windage ports.

 

[vitesse]

Great thread this,Dave -you almost sound like the UK expert by now.Have you got a bed down at your specialist?[]

 

[Eldavo]

I don’t have a bed there but I may as well set up a Direct Debit.

I’m not an expert - I know what I am doing and why I am doing it but I don’t always understand the technicalities behind it. I refer to friends in the Uk and USA that do, but would never dream of passing this off as my own knowledge. He who shouts loudest and types longest isn’t always right.