DDK - Die Deutschen Klassiker

Yesterday was mainly playing, fitting the various crankcase ancillaries. I started with an easy bit, and added the new heavy duty alternator earth lead. Then onto the triangle of leaks, where I fitted the breather (needed the engine lifting eye removing first), the oil thermostat and a new oil switch.


Then came the oil pressure relief valves, using the later caps (hex head rather than the screwdriver type), new springs and pistons. I even remembered that the one with the longer spring has a spring support tube (or something like that) and goes on the side of the engine.


Chain ramps were next, where I also remembered that the lower right side is brown and all of them have the longer edge pointing towards their nearest sprocket.


The car came with a later sump plate, one without a drain plug so I sourced an original type. I was going to fit it, but when I accidentally dropped a nut and it conveniently fell through the engine and out of the sump hole, I decided that the sump plate can wait .



Onto today, and time to plan for measuring CRs, deck heights and valve to piston clearances. I cut a nice circle out of acrylic sheet and drilled a hole in the middle – all ready for ‘burtetting’ in liquid to determine cylinder head volume. Wayne’s performance book recommends solvent and ATF when measuring volumes. I have ATF but what ‘solvent’ should I use ? – maybe brake cleaner ?

I played around a bit, making plans for proper measuring and decided that piston ring gapping should probably come first.
You will (maybe) recall that I have 98mm Wossener pistons and their notes advise 0.004" x bore (in inches) for the top ring and 0.005 x bore for the second ring. The oil ring is spec’d at just >0.15 thou. So for the top ring, I calculate 0.004 x 3.858" as being 15 thou, or 0.39mm and for the second ring I calculate 0.005 x 3.858 as 19 thou or 0.49mm.
Porsche (for a '79 SC engine with 95mm pistons) stated 0.4-1.4mm for the oil ring and 0.15-0.3mm for the others. As I understand it, thinking has moved on and the gap for second rings is now suggested to be larger than the top ring, to reduce oil consumption. However, IIRC, the ring gaps quoted by suppliers are generally suitable for water cooled, steel block engines, whereas this is an oil cooled aluminium engine.
I have only just started to check, and with my first set of rings and cylinder, I have 0.28mm top and 0.35mm second ring gaps, so they need appear to need filing (as expected). However, before I file bits off, and recognising that filing bits back on is harder, does using 0.38 & 0.5 seem reasonable (close to the Wossener numbers but tweaked to suit my feeler gauges) or should I leave them tighter ?? In which case, how tight ?

Today was cylinder head volume measurement playday (well it was when I started writing this anyway – time has moved on). I set up the burette and stand, got the cylinder head ready, together with the acrylic disc I had cut out. But what to use as my fluid. I tried ATF – easy to see, but a huge meniscus and it took over an hour to drip out just under 90cc to fill the head chamber.


I drained the burette, cleaned the cylinder head and tried some old petrol, with a splash of ATF to give some colour. That ran out much better and with an easy to read meniscus. The downside was that it found its way past the tap of the burette.

Next up was a 50:50 mix of petrol and ATF. Poured out reasonable well, and didn’t leak from the burette. Downside turned out to be trying to purge all of the air from the cylinder head. With both the ATF and almost neat petrol, an air bubble formed under the acrylic sheet. By playing about and gently sloping the cylinder head, I managed to get the bubble under the filling hole and purge it out / displace it with more fluid. With the 50:50 ATF/petrol mix, I gave up in frustration.


A new day and I tried brake cleaner. I also drilled an air vent hole right at the edge of the cylinder head (in the acrylic, not the cylinder head).

This worked well. The only downside, was that as I was being a cheap slate, I reused the brake cleaner. Unfortunately it washed off some of the grease I was using to seal the acrylic sheet to the cylinder head and that occasionally blocked the burette, or at least partially blocked it. I tried to clean it out with needles and various other implements, all quite unsuccessfully. Finally I discovered good old fashioned fuse wire did the trick.

In the end it took me three days to check all my cylinder heads so that I was happy with consistency of results. I had 4 heads measuring 88.8cc, 1 @ 0.2cc above and the other 0.2cc below. I think that’s an acceptable tolerance.


Next day and onto the joys (and scariness) of ring gapping. Watch a few YouTube videos and scare yourself about burrs, broken rings, etc, destroying your engine, then proceed on your own rings.


Following the underwhelming advice on ring gaps, I stuck with what Wossner stated. I needed 0.39mm for the top rings, which were all around 0.28. I added a second ring to a piston and used that as my depth setting tool for consistency and levelness. I checked for a slightly loose 0.38 but not quite 0.40mm. Second rings were all about 0.45 and needed relieving to 0.49, but as I only had 0.45 and 0.5, I chose the latter.

Oil support rings are >0.15thou, or 0.39mm. They were a nightmare. Using the piston to ensure they were level was fine until I pulled the piston out. The oil support rings are so light that they lifted out, chasing the piston. In the end I put the second ring back into the cylinder and added an oil support ring above it. By levelling that lot together, I could ensure that the oil support ring was tight to the top of the other ring, also knowing that the second ring gap was bigger than the desired oil support ring gap. They only needed the least clearancing, with the top rings needing the most.

All now done, but as it was starting to get cold and I was unsure how, if at all, that would impact the cylinder and ring & therefore the gap measurements (or more truthfully, I needed a wee), I called it a day.

Do professional engine builders go through all this palaver? Might explain the extortionate cost.

Gapping the rings for sure is necessary (maybe the Porsche standard jobbies are OK out of the box, but ....). Checking CR and piston to valve clearance is necessary with new (to me) cylinders, skimmed heads and domed pistons - select base gaskets to suit.

The Pros probably don't spend so much time procrastinating and worrying though

Great work Peter. Good call on the rod bolts, I’d put reasonable money on them being absolutely fine (I did mine the same) but if it’s in your mind it’s not going away!

Maybe you had no advice on ring gaps as no one has any real idea Going with the manufacturers numbers has to be your best bet.

Agreed Gary, it's the trouble with doing things yourself - if there's a dodgy bit of meatlwork, I would always see it / know it was there. Similarly with the engine, if not 100%, then I would always be worrying.
In better news, there's an engine build finishing on IB using Wossner pistons and late yesterday they confirmed that their builder had used 0.4mm, so that's comforting.

PeterK wrote:Agreed Gary, it's the trouble with doing things yourself - if there's a dodgy bit of meatlwork, I would always see it / know it was there. Similarly with the engine, if not 100%, then I would always be worrying.
In better news, there's an engine build finishing on IB using Wossner pistons and late yesterday they confirmed that their builder had used 0.4mm, so that's comforting.

Admirable eye for detail as always mate.

Absolutely right always trumps near enough.

Or, as we Scots would say, you don't want it oot by a baw hair

Well worth the slog though never done it myself on any of the engines I've done. 10/10 for perseverance!
Bob Watson used to do all this type of work on hot engines hence him saying it takes 2 weeks to re-build the engine (after ALL the prep is done on the parts)

Looking forward to your work on timing the cams.

So with top ring checked and set at 0.4, second ring at 0.5 and oil rings at 0.4, we are good to go. There has been a short intermission, including spending two days stood on the roof of a neighbour’s shed, gradually logging the ginormous tree that had decided to gently keel over and rest on the shed roof. I now ache in places I didn’t know that I had – clearly I had my feet in strange positions to balance, either on the roof, on a ladder or stood on branches as we gradually dismembered the tree. At the base it was only about 750mm diameter – my big chainsaw only just went through it.

Anyway, I digress and a small confession now…..
I reviewed my GoPro footage of putting the crankcase halves together and it was just over 45 minutes. Also, I had an aftermarket kit of seals and gaskets, including the blue through-bolt o-rings. After building my first 911 engine (assuming that I ever finish it), I may choose to do more, and had an opportunity to understand better the effectiveness of my spreading sealant, the impact of taking more than the mythical 45 minutes to seal the crankcases, etc. Only one way to find out ….. pull ‘em apart and see. What did I find – not much. Sealant spreads very thinly, but there were a couple of places that looked like there was a small clump of 574, and both clumps were in the main bearing journal gussets, so that makes me thing that it was a good move to split again. The good news is that all the o-rings were sound, with none ripped or compromised.

The down-side is a whole heap of cleaning again, a new tube of Loctite 574, a pack of genuine Porsche o-ring seals and replacement perimeter lock nuts. I also elected to use a genuine Porsche rear seal. Anyway, after lots of cleaning, a bit of lubing and suitable application of sealant



I joined them together (again)


This time I’m not using RTV on the through-bolt o-rings (while Wayne’s book recommends it, I’m not so sure that he still does). I hated the idea of RTV near my oilways and it was a right bu$$er to clean off my through bolts. This time I’ve installed my through bolts without o-rings. Panic not, this is temporary, but it made sure that I was not delayed trying to lube the o-rings. Lubing was worse when using RTV as it goes off, and so couldn’t be done in advance. It was coating the o-rings that really took too long and caused me to over-run the 45 minutes. I’ve also chamfered the left side crankcase bolt holes (only the RHS is chamfered originally, which is why you need to put the bolts in one way, hold the bolt heads without them turning and only tighten the nuts to avoid damaging the o-rings. My plan is to remove the through-bolts one at a time and add the o-rings, using silicone grease as my lube.
I then added back the chain ramps, breather, oil switch and PRVs.


Time then for the cam carriers. On one of them I found a broken stud in the 3 in the back end, next to the camshaft blanking Welch plug. There were a further 2 broken studs on the top, where the tinware bolts on.

I drilled the one next to the Welch plug with a left-handed 4mm drill, but it stayed fast. I then drilled it out further with a left-handed 5mm drill. I had not long started and it spun the remainder of the threads out nicely. Result. Unfortunately the two on top of the cam carrier fought back. I ended up drilling them out and heli-coiling.



Then time to pull out the oil squirter tubes. As reference shots, the pin that retains the squirter in the correct orientation and placement goes on the rear side of the engine – at the Welch plug end.


…and the oil feed to the squirter is at the end you load the camshafts.



General advice is to drill and tap the aluminium plugs that seal the oil squirter tubes and extract using a 6mm bolt with spacer. In my case read small socket.


That worked on 2 of the 4 plugs, with the other 2 being somewhat stubborn and needing more drilling and then careful thinning and collapsing to remove. Nevertheless, tubes removed



More reference shots. At least for later cars with the 4 bearing camshafts, the oil squirter tube is handed and must be fitted a particular way around. When it is correct, the big oil holes line up with the dimples (that seem to serve no other purpose) on the camcarrier.


If you get it the wrong way around, then the holes do not align with the dimples


In terms of orientation, the retaining pin

in the hole in the end of the squirter tube, but there is a hole on both sides.


When it is the right way around, then looking from the inlet side, you can see a single small hole


Please shout if I have messed these reference shots up, but I hope not.


I’m also fitting oil restrictors to the cam oil feed.


And you can see the new oil restrictor on the left, versus the original feed union on the right



Cam carriers now cleaned internally and squirters and fittings loosely reassembled, but they need degreasing and another clean before trial fitting when I check piston to valve clearance shortly.

- impressive work !!

I wish I had the bottle to tackle an engine build

It’s really quite a simple concept - I’m too stupid to know that I can’t do it, so I just crack on

And there we were thinking the valve clearance checks on our VTECs were a spherical ache

PeterK wrote:It’s really quite a simple concept - I’m too stupid to know that I can’t do it, so I just crack on

.... it was Wayne Dempsey's book that finally put me off - I'm sure that's why he wrote it

Doing a stock 911 air cooled engine is not difficult, tricky in places maybe and you need good attention to all details, but that goes for every engine.

I've done 4 and find the cam timing the hardest to reason with, but all down to preparation and the Dempsey book (that I've used on the last 2 rebuilds) is well designed to get you all ready for the stage of the build being undertaken.
Worst part is the feeling to rush the assembly where case sealant is involved.

'Cleanliness is Godliness' and all that.

911hillclimber wrote: I've done 4

Four!!! How long did it take the first time, and the fourth? I think the time period scares me the most - I imagine that if I started it, it would take me 2 years to finish it, but if I give it to an engine builder, it will take them 2 weeks, and they wont get all the grief from the missus....