The Manhattan Project

Ongoing and archived Porsche (and other marques) restoration threads from DDK members

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AndrewSlater
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Re: The Manhattan Project

Post by AndrewSlater »

jjeffries wrote:Thanks very much for documenting this; I have an 82 SC and am a CIS appreciator so all relevant and fascinating content for me.
Would the blocked return line have showed itself in fuel pressure tests (as shown in Bentley, CIS manuals, etc)?
How are you measuring CO? I put an AEM gauge in mine, but now keep a cover on it because I don't need to be looking at it all the time. That in turn makes me think a decent sniffer would be better...keep it in the garage and use it on any car.
Your car is stunning.
Best, John
Hi John, yes the blocked fuel line showed up in the system pressure test. When I first tested the CIS I did all that off the car, but had tested it again when the engine was refitted and first run in the car. Sadly it was when I refitted the engine after fixing the bent clutch arm that I introduced the fault - which then killed the FD and the subsequent rebuilds until I spotted the error.

I am measuring CO myself with a Gunson Gastester which puts you in the right ballpark.
Image
The spec for the car is 1.5 - 2.5% but I'm currently running fractionally richer to reduce a bit of popping on lift off.

The car runs pretty well but has an occasional slight hesitation in the 2K-3K range. It idles really well and above 3K it races to the redline pretty rapidly so all good there.
Now reading around some people say the cars were delivered in '74 with this 2-3K hesitation problem from new as CIS was quite immature, whereas others seem to be able to fix it by tracking down an air leak or changing the timing map, etc, etc.

I've just bought a smoke machine to see if I can identify any air leak, and then I was considering trying a 123ignition distributor in the future, as I may be able to map out the hesitation by adjusting the advance curve.

At the weekend I swapped the distributor cap and rotor. I was running a 7k1 rev limiting rotor but swapped it out to a 6k5 one I had bought. However I had bought two rotor arms and neither worked as both were open circuit! ( You can't trust new parts to work out of the box ). I put the 7k1 back on and the car seemed to drive better again with the different distributor cap.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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AndrewSlater
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Re: The Manhattan Project

Post by AndrewSlater »

johnM wrote:What a great result Andrew, top marks for perseverance, many would have given up.

Sounds like you are just about there. :cheers:
Thanks John - yes other than this subtle hesitation issue it's pretty much done.
One final job is to take it in to a specialist to get the suspension geometry set.
Considering I set it all up myself with string and rulers it sits and drives really well.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
The Other Stu
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Re: The Manhattan Project

Post by The Other Stu »

I hinted back in May about taking it to Bicester.

Another event coming up in early October.....
https://www.eventbrite.com/e/sunday-scr ... 5095523463
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Re: The Manhattan Project

Post by jjeffries »

Andrew, I bet you got the alignment right using strings. John
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Re: The Manhattan Project

Post by 911hillclimber »

Works for me, esp if you have a simple camber/castor gauge too, only corner weighting that will allude you, total cost £17.
Use the same on my race Lola too.
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Re: The Manhattan Project

Post by AndrewSlater »

The car has been almost finished for a while now, but needed a few final tweeks.

The main issue was around driveability but that proved difficult to solve, so instead I fixed some of the easier and more satisfying things.

Firstly I wanted to change the steering wheel for something smaller as my thighs would catch on the original wheel getting in and out of the car.
So I bought a cheapo Prototipo replica to see how that felt. Much easier to get in and out with the smaller wheel - maybe I should buy an original one at some point.

Image

Secondly I'd had a lot of comments that the reflective number plates looked odd on the car. To me they look period correct but I thought I would change to the black and silver to check out the look.

Image

The next tweeks were more engine related.

I found that the oil level gauge was reading a little low, compared to the dipstick, which I found annoying.
I duly removed the oil level sender and bent the float arm in an attempt to recalibrate the reading.


The next issue was engine driveability. I'd been making trips to run the engine in and set the mixtures, but found that the car had a slight stumble and hesitation between 2K - 3K rpm.
Driving on the 50mph roadworks on the M27 near me was a pain. Both 4th and 5th fell into the dreaded rpm range, and made driving a bit uncomfortable and I had the feeling it wasn't doing the engine any good.
Mind you changing down to 3rd fixed the problem, but I got quite a few strange looks.

Reading up on the issue there's plenty of people reporting the same issue with a myriad of suggestions for fixes. It felt to me like a mixture issue, so my first port of call was looking for any unmetered air leaks in the system.
I duly bought a cheap smoke machine off eBay, and injected smoke into one of the injector ports, looking for leaks. This worked a treat as a means of diagnosing the system quickly and I quickly found a slight leak from the airbox.
The leak was quite small but worth finding, after making a repair sadly it didn't change the symptom.

I finally put the car back in the workshop to force me to fix the problem before putting more miles on the car, but as usual life got in the way and things have taken longer than I expected.


After more research I realised that the WUR pressure figures I had used from Jim's CIS Basement were very different from the Bosch K-Jet Workshop manual.
I'd setup and tested the WUR on it's own, but my car has a throttle activated valve that also controls the system fuel pressure, in effect richening the mixture at idle and full load.
Jim's CIS Basement figures had no consideration for the TAV, and even if used as standalone figures were incorrect for the '74 car.

Retesting my system it was soon clear that the WUR wasn't set to the correct figures. Configured without the TAV in the system, the warm pressure should have been 3.6bar nominal ( mine was set to 3.0bar ).

I bought a WUR rebuild kit from Colin at KJET.BIZ and rebuilt the WUR. Colin sells quite a comprehensive kit and can also supply new heating elements for the bimetallic strip.
I decided to setup the WUR on the car system, but temporarily lengthened some of fuel lines to allow me to calibrate the unit outside the engine bay.
Image

I soon had calibrated the WUR for a warm pressure of 3.6bar, and then set the cold pressure accordingly.


When I reintroduced the TAV however the idle and full load tests didn't give quite the right values, close but not quite within spec.

I bought another TAV from Germany and opened it up to have a look. I had previously bought the WUR rebuild kits from Colin at KJET.BIZ, and asked whether anyone makes a TAV rebuild kit - but apparently not.
I cleaned up the TAV as best I could, relubricated the cam, replaced the crumbling sealing foam, rebuilt it and fitted it.
It's not clear how you would disassemble the valve further to rebuild it if a kit was available.
Image

With it all plumbed back in - success.

Image

A part load pressure of 3.6bar, and idle value of 2.9 bar and a full load value of 2.8 bar - bang on! ( Assuming my fuel pressure meter is accurate )

So I now need some dry weather to get the car back out to get it up to temperature, reset the idle mixture back to spec and hopefully the stumble will have gone ( or at least subsided ).

I'm feeling pretty confident that it should be fixed / improved ( but then I've been confident before ).
I just need a dry weekend now.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
Lightweight_911
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Re: The Manhattan Project

Post by Lightweight_911 »

.
Excellent progress !!

.
Andy

“Adding power makes you faster on the straights;
- subtracting weight makes you faster everywhere”
sladey
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Re: The Manhattan Project

Post by sladey »

Impressive analysis
The simple things you see are all complicated
I look pretty young but I'm just backdated yeah
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Re: The Manhattan Project

Post by Gary71 »

I understood the ‘fitting a smaller steering wheel clears my legs’ part, the rest? not so much :)

Whatever it is you’ve done I really hope it works and you get out driving before the last and snow arrive!
911hillclimber
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Re: The Manhattan Project

Post by 911hillclimber »

Ref: Steering wheel:

I had an prob too with my proto tipo in my lap (I like a wheel high up) so fitted an eccentric spacer to raise the wheel about 12mm up and 10mm towards you.

Superb mod for £20 off ebay. Horn etc all ok, 15mins to fit if not in a rush.

Ref plate, all subjective but it certainly looks the date on the car in B&W but I like the reflective type on my light yellow 911T, but the colours blend together on my car.

Your car is superb and very unique, and all the engine work you are doing is very brave in my view and getting these results a credit to your understanding and determination.

Hats off to you. 8)
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Lola t 492 / 3.2 hillclimb racer
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Re: The Manhattan Project

Post by Dougieboy1 »

keep ticking things off on that snagging list!!

Personally, love the contrast between the excellent body colour and the black plates but i realise this is a personal thing......

Fantastic result so far, you must be very happy and forgetting all of the previous hiccups!
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Re: The Manhattan Project

Post by Northy »

I’ve had similar stumbling from my CIS SC. I went through a similar process to you. I found conflicting information on the correct WUR readings, some don’t mention that for some vehicles you need to apply a vacuum to the WUR (in the Bentley is days fun the engine, which will apply the vacuum) during the tests. This dramatically changes the readings.

After doing lots on fueling, resetting pressures etc I think my root cause was actually a dodgy new rotor arm. So don’t completely rule out spark. Check the green wire from the dizzy to the CDI as well.

It is satisfying when you get it working though! Good luck!
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Re: The Manhattan Project

Post by AndrewSlater »

Thanks for all the great comments guys.

Ref the steering wheel offset spacer, do you not get the problem of it digging into your legs further when you turn the wheel by 180 degrees?

As for the black/silver plates the look has grown on me.
When I first fitted them I had a sense of deja vu but couldn't think why.
I later spotted Angus' '74 911 that I have seen in the flesh a few times over the years and the penny dropped.
Spot the difference ( I hope Angus doesn't mind me using his photo ).

Image
Image

Before testing out the fuel pressure mods, I thought I should finally fit my engine bay stickers that I bought from Carbone.
Image
Perfect - bound to jinx it!
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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Re: The Manhattan Project

Post by 911hillclimber »

Ref: wheel
Nope, not in normal driving with hands at 10 to 3
You really do not notice the eccentricity, many moderns have the wheel rim eccentric to the steering column shaft to a far greater extent than this adaptor.
73T 911 Coupe, road/hillclimber 3.2L
Lola t 492 / 3.2 hillclimb racer
Boxster 987 Gen II 2.9
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Re: The Manhattan Project

Post by AndrewSlater »

911hillclimber wrote:Ref: wheel
Nope, not in normal driving with hands at 10 to 3
You really do not notice the eccentricity, many moderns have the wheel rim eccentric to the steering column shaft to a far greater extent than this adaptor.
Thanks Graham - Sounds like a good option then - I'll keep my eyes out for a cheap adaptor on eBay.
1966 Porsche 912 Slate Grey, red interior - first owner owned for 41 years
1974 Porsche 911 2.7 (The Manhattan project) viewtopic.php?f=28&t=51455
1973 VW 914 1.7 Olympic Blue - ( gone to a good home )
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