A6 TAU - Atmo

Lighting captions in wrong order - sorry!

I’m delighted to announce that I now have an MOT!!! Even better, there were no advisories.

On the down side, she did break down on the way home - battery has been on its last legs and finally packed it in. Fortunately, it conked out outside the local pub where the garage owner was having a pint! He nipped out and helped me restart it and I nursed her home. New battery is on the way.

The only problem I have spotted on my first drive is that a bush on the rear drivers side is creaking. Searching on here that seems to be a common complaint, so I shall ignore it for now!

Update for the New Year!

Well, since my last post I have had the engine and gearbox out for a clutch change and replaced all the hydraulics.

The key development is that I have replaced the Solexes with a tweaked Weber 38 DGAS sitting on a raised mount but still under the old airbox. So simple to install and operate and straight out of the box the car runs smoother and with almost no hesitation. The torque is immense. It makes blasting up the local winding lane and absolute pleasure. Once it has had a proper tune, I think this Atmo will be one of those cars you never sell.

The only downside is that the passenger window has decided that it isn’t going to close - annoying - it’s a dodgy connector but it takes a few minutes to get at it.

Happy New Year!

Phil

[mettersl]

Well done Phil,
Welcome to the world of working Atmos, apparently there are 25 of us in the UK.
What did you need to tweak the 38DGAS to get them to work properly on the Atmo?
I'm running Solex now and they are OK, but always interested in simple, reversible mods that improve it, the holley has always been a bit too much of a one way mod for me.
I had the same problem with the left window, but its settled down and works reliably now. You can clean the connectors with the motor in place if you are flexible.

Good to hear that I am not alone!

I will revert With details about the Weber conversion......

Hi phil would also be really interested in fitting the weber does it come as a kit? Any info would be apprecieted. Thanks brian.

[stephendell]

There was an oem Weber manifold available for the R20/30 if you can find one. It’s a direct bolt on replacement but there aren’t many left that haven’t been chopped up by Johnny law for Holley kits along with the solex ones.

Sorry for delay since last post although i think I have answered the questions in some PMs.

In essence, the conversion is like the holley in that that manifold is cut open and a weber mounting plate welded on. My weber is on 2 x rubber mounting blocks which gives a better gas column but it still fits under the engine cover with the original airbox.

I think the holley flows more vapor, but the weber seems to flow enough and the car is very nice with it.

Ive just fitted a throttle return spring to get a perfect pedal action. I also has a minor problem which apparently is common with the 38 DGAS - the brass pipe for the fuel inlet to the carb was slightly loose and therefore leaked. I have bonded it in with epoxy as per the 1980’s tried and tested fix.

Just need to refix the passenger window motor, get a respray and sort out the turret pockets and then drive her!

Incidentally, if I fit a rear turret brace, can I drive her with dodgy turret pockets until fixed?

[johnb]

Well done Phil,
Welcome to the world of working Atmos, apparently there are 25 of us in the UK.
What did you need to tweak the 38DGAS to get them to work properly on the Atmo?
I'm running Solex now and they are OK, but always interested in simple, reversible mods that improve it, the holley has always been a bit too much of a one way mod for me.
I had the same problem with the left window, but its settled down and works reliably now. You can clean the connectors with the motor in place if you are flexible.

Good afternoon Lee,

It's pouring down here and I should be in the garage fitting a new clutch master cylinder to my A310V6 but my thoughts have drifted to carburettor conversions again, as a maybe. Mine runs OK but not perfectly in that 1000 to 2000 rpm rev range, hence the maybe thinking. By the way I've changed the slave cylinder, being the easiest of the two to begin with, and found it was leaking slightly. Whilst the car is blocked up to check the gearbox oil level I'm going to change the master cylinder also.

In your post above you say that you consider the Holley conversion too much of a one way mod. I'd be interested to know what you meant by this, if you could advise.

[mettersl]

Hi John,

Fitting the holley means cutting and welding your inlet manifold up and leaves a large hole with a Holley mounting plate in it. If you decided to go for another option later you will need to fabricate an alternative mounting plate. This is what I meant by one way modification. You have to have a second manifold if you want to go back and they are getting in short supply.
The 38 DGAS is the right kind of size for the engine and reverting is also more straightforward, but in the end it's all personal preference. I was heading this way, but decided to stay stock.
The Holley seems to be a successful mod for top end power, but the carb is big for the engine size and I'm told that you need to work on things like the springs that open the second set of barrels and getting it jetted to suit the engine. At low end it risks being just a bit too big for the engine etc.
I must be wrong on this as most people prefer it, but one of the delights of the Solex carbs is the massive bottom end torque and responsiveness combined with good top end.
Yes they look complex, but actually they aren't, the "big carb" barely has any adjustments and the small one only adjusts at idle.
At the moment my Atmo is up for sale, but if it doesn't sell, I plan a 38DGAS style throttle body injection conversion to try and get the economy better as (less than 27MPG) is a lot less than Tony is getting from his injected atmo... (although realistically it's not needed, it's just that toy car playing about thing...).
Lee

[johnb]

Hi Lee,

Agreed, without a spare manifold it would be a one way modification and commitment.

When I bought the car the carbs were in poor condition. Some years ago at the Silverstone Classic I had a chance conversation with the owner of a Lancia Stratos replica (Hawk) who also owned an A310V6. I mentioned that I was looking for some carbs and he advised that he had a secondhand set of both carbs including the manifold. A price was agreed and a few days later they arrived. These are the carbs currently fitted to the car which I refurbished with the usual gasket, etc kits at the time. I still have the manifold and I think it would make sense to hang on to it in case I go for the Weber. Finding the correct information regarding jetting, etc might be a problem as well as finding the correct dimensional information regarding the manifold and air filter modifications.

I agree that there’s little adjustment possible with either Solex carb but it feels as if I don’t have the single choke carb quite right. My starting point has been a post I read on the FAR forum that recommended 1 1/2 turns out on the air screw (top) and 6 turns out on the mixture screw (bottom). I’ve been trying to find that post again without success at the moment.

I run the Holly and spent a lot of time getting the jetting right, I would have to take them out now to find what I have in it, but I cannot fault the performance when it’s right very fast response and good economy unless you like the loud pedal. But the real let down is the distributor with its weird ignition curve and old Ecu lower down which gives you a small flat spot.
To that end I have bought a mappable ignition which I have fitted and looked really simple to setup but I never learn, anything to do with computers is never simple and not being any good at programming the program was written for windows XP and our laptop won’t recognise it cannot win, I always try to keep electronic stuff out of stuff as much as possible but sometimes you have to give into it.
.

[johnb]

Must admit that the absence of electronics on the A310 suits my abilities better. However, I did change the points to a Limenition electronic system. Had some initial teething problems due to a manufacturing error but, once corrected by Lumenition, it’s performed well.

Hi I have a 310 distributor and have thought about fitting it to my Atmo with what you have done.
The carb upgrade will transform your engine, the solex is not a very good carb and far to complicated,
Unless you are a purest and doing concourse events reliable and easy servicing is the way to go so you can just jump in and go.
The old carbs will all be suffering whear and tear jet tapers and the spindle bush’s which unless you are going to spend a lot of money for a professional rebuild it’s not worth it.

[mettersl]

If you have a second manifold, it's a simpler choice. Weber conversion is less metal hacking than the Holley.
There was a lengthy thread about all this on one of the facebook forums recently with the Guru's - Martin F, Dave G, Stephen and Lee C. There are quite a few differing views... !
Is your engine/exhaust standard otherwise? Bear that in mind as some of the examples have free flow exhausts and polished heads and or cam work too.
I am lucky, my car has only just passed 70k and the original carbs are in good condition.(the benefits of 20 years in storage).