'73 modified E rebuild

[Tony]

Sorry guys!
I wanted to see how this turned out before posting and I'm afraid it has simplified things and removed the real drama.
In reality I was in a state of panic both from the thought it could all go wrong and the thought of the bills!

I'll stop mucking about!

[911hillclimber]

I thought you seemed to be taking it all so matter-of-fact!

Getting through these dilemmas is always nerve wracking and expert help is always really expensive, but those CNC machine tools are v expensive to repay.

Good progress I hope (are we in real time now? ) and you will soon be back on a hill!

[Gary71]

Looking good so far! Any chance you could accidentally draw round the chain and rod supports as I need to make a set

[Tony]

Back to real time very shortly!

And Gary, I'll see what I can do.
Meanwhile!
With the bottom endd back together it was on to the next issue. Because the barrels and pistons were in excellent condition the intention was to reuse them. However we didn't know the original compression, the barrels were 1st oversize and sat on 4 base gaskets! So certainly not standard.
Next step then was to measure combustion chamber volumes, check that there was adequate piston/valve clearance and work out the compression ratio.
To do this meant building up everything for at least 1 cylinder and a partial build of a complete side.



Old and New camshafts - something odd about one of these.

This was too important for me to be let loose on so Paul did the measuring.


Good piston clearance


Time consuming to do properly but well worth it. Everything checked out and compression ratio was, as expected high with only a single gasket.

By calculation the compressions were as follows:
Number of Base Gaskets 1 Compression 11.4:1
2 Compression 11:1
3 Compression 10.7:1
4 Compression 10.4:1
So back to the 4 base gaskets then! This was a bit high but with 97 or 99 octane and the use of the 123Tune programmable distributor not something that should cause a problem.

So now the build could continue. After the pain and delays of getting to this stage I was waiting for the next problem but barrels/ pistons fitted, heads,built up and fitted, cam carriers all went together fine. Even the cam timing was done without drama.





And the bloody expensive oil cooler gets its own picture!


Nearly there!

[Tony]

Everything else went to plan, although correctly drilling and fitting the new engine shroud took some time (possibly because I was trusted with doing that!).
With the shroud fitted all the other ancillaries could go back






The SSI's that were on originally went back and with a new clutch installed the engine was hooked up to the gearbox and refitted in the car.
With the fuel pump off and no ignition the engine was turned over to get some oil pressure up.
Then the 123Tune distributor was refitted.


With engine at TDC for cylinder 1 the distributor was inserted with the rotor arm roughly pointing to no.1 on the cap, plug in the laptop and gently rotate the distributor body counter clockwise until the led lit. That was it! With distributor cap back on and fuel primed, time to turn the key! After very little cranking the engine fired, and died, second try and it fired and cleared very quickly settling down to a steady idle Then we all stood underneath and look for oil leaks.



Dry as a bone!

[Tony]

So that's it really.
The car is now back home,


it has a couple of hundred miles on it, (cut short by weather, so it'll get a little bit of running in, then an oil and filter change, check valve clearances, rocker bolts etc.
Final step will be off to the rolling road for final setup an to get some figures.
When I'll update the thread in real time! Meanwhile, my huge thanks to Gantspeed, not only do I have a good engine, I've learnt a lot and save a small amount of money!

Worth at this point highlighting a few things learned:
1. It's never going to be as easy as it seems and won't work out how you plan it
2. These engines can absorb a huge amount of punishment and will still run well with a whole raft of issues that would stop most 'water' cars.
3. Because of 2, when rebuild time comes there's going to be a lot more to replace than you think (or hope)!
4. Parts are readily available – though not always immediately or at a price you'll like
5. Expertise is not always as available as you'd think
6. The hours of work involved in going from 'Sick Engine in Car' to 'Good Engine in Car' is huge. I think Bruce Anderson's book quotes 50 hrs to rebuild a 911 engine, excluding prep, problem solving along the way or specialist machining.

[911hillclimber]

Excellent, great result.

Bob Watson told me 40 hours to clean and prep, 40 hours to build and run.

I am still taken by the 123 distributor. hope you will detail the full dialing-in experience for me/us.

my last re-build was my hillclimb 3.2 engine after a major 'incident' in one cylinder at 6k rpm. The barrel split top to bottom ...

I found one of the specialists I used coming very short of skill and professionalism but good at asking for top money.

Something to be learnt every time.
Thanks for the write-up.

[Tony]

Thanks for the comments Graham, the 123Tune should be interesting, I currently have 2 maps that were developed with the previous cams, 1 is a safe option, less than optimal advance, gentle curve lower rev limit, the other more radical with steep advance to 38degrees 7300 limit.
So far both work but the radical one doesn't drive nearly as smooth as before - at least while keeping under 5000rpm.
Will keep you posted.
Tony

[Kneeslider]

Excellent, great result.

Bob Watson told me 40 hours to clean and prep, 40 hours to build and run.

I am still taken by the 123 distributor. hope you will detail the full dialing-in experience for me/us.

my last re-build was my hillclimb 3.2 engine after a major 'incident' in one cylinder at 6k rpm. The barrel split top to bottom ...

I found one of the specialists I used coming very short of skill and professionalism but good at asking for top money.

Something to be learnt every time.
Thanks for the write-up.

Nice. You made a proper mess of that one! Seized big end?

I missed a whole summer of bike riding last year because my 900ss ate it's desmos, and dropped an inlet valve in. Fortunately it started rattling before letting go, and I had just about got it stopped when the valve dropped. It was my own fault though, because being clever, I had adapted a set of 4 valve Ducati SPS adjustable cam pulleys to fit on my 2 valve engine, which needed shimming up so the belts lined up OK. I made the shims on the lathe, and fitted them up, but my manufacturing tolerances and material spec weren't up to the job, as the vertical cylinder pulley fretted on the shaft, and wore away my shim, and eventually sheared off the key. The timing then went off, causing the piston to contact the valve, though not initially catastrophically. With everything banging around, the valve stem shim came off, then the collets came out and the valve dropped, bent and shattered the valve guide.

Still, all the mayhem only cost £450 to sort out, but several months sourcing parts. Ducati wanted £95 + VAT for an inlet valve, but alternatives are out there.

For some reason its always good to take pictures of the results of mechanical mayhem.

[911hillclimber]

Never really found out why, even Bob could not give one failure mode.

£3000 bill and I did the rebuild!
The bottom of the piston fragmented and went everywhere in the engine, all the valves were bent in all the cylinders.
The rod stopped me taking the crank case halves apart it was wrapped round the internal webs.

Not much damage to the mighty 3.2 case! Really tough engines.

Please detail the 123 mapping for us!

[Tony]

Today was supposed to be final setup and power test on the rolling road. However net result was a difference in fueling between the 2 banks of cylinders above about 4000 rpm which stayed no matter what we did.
Diagnosis is at least 1 faulty injector - can they be cleaned and tested? Shocked by the price of new ones.

Tony

[sladey]

Yes they can - I had mine done but can't remember who by. IIRC it was about 100 to clean and test all 6

[911hillclimber]

I know you can get Subaru Impreza injectors cleaned and matched at the same time, but mechanical injectors might be tricky, though have you tried the people who re-build the pumps for these cars?

[jtparr]

Yes they can - I had mine done but can't remember who by. IIRC it was about 100 to clean and test all 6

Was it Fred Pentecost at Tower Diesel..?...

[Tony]

Ended up changing all the injectors. So back to the rolling road and instantly the fueling problem was cured. However that was the only good news, we started with a strange noise, no changes to ignition or fuel settings were making much difference. The car was reluctant to rev and the noise was getting worse. This became a definite 'chuffing' sound – head gasket on an engine with less than 2000miles? Clearly we were in deep trouble. So, rolling road session abandoned, back to Gantspeed.
Once the engine was out the car the injection and exhaust were stripped off. Rockers cams, timing chains etc. all removed, all showing signs of an engine bedding in nicely!
Cam carriers off it was time to take the heads off an see what the hell had been going on.
First, heads were removed from what we believed to be 'good cylinders', every thing looked fine until we looked at the head gaskets on all of them the inner spring element was showing lesser or greater signs of breaking up. On the other side it was exactly the same only 2 cylinders the break up was sufficient to allow the outer part of the gasket to distort and leak.
This all caused considerable consternation from those with over 40 years building 911 engines!
Much head scratching and careful measurement follows and the result surprising.
It transpired that the head gaskets (from a full gasket set of the original OEM supplier) were too thick (checked against an 'in stock' item supplied by Porsche) and were not allowing the heads to sit correctly on the barrels. A set was ordered from Porsche and these proved correct. A second full OEM gasket set was opened and these were to thick.
So it would appear you can't trust anything anymore and at least one engine builder now measures gaskets and what's next tensile strength of fasteners?
After this discovery the engine was fully rebuilt – with the correct gaskets. Fuel and ignition were reset, everything checked out so another rolling road session was booked.

Back on the rolling road Johns approach was to first find an acceptable ignition map which would give clean revving without load and a total advance which fro experience would give a good starting point. the last ignition map we used, although the car would run with it was not good. We reverted to the map we'd developed last year before the rebuild (the major being S cams instead of after market). This was ok giving over 180 bhp but the fueling clearly wasn't right. Adjustment to the pump brought improvement. eventual giving 202bhp and 174ftlbs. This was pretty good, a road test showed clean running and the ability to run at 2000rpm in top - not really the idea but some measure of flexibility.

So now it gets used, need a few decent trips organised, track-day booked at Blyton at the end of the month after which, desperate for the odd sprint and hillclimb.