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.
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.
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.
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.
With it all plumbed back in - success.
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.