Subject: Twin carb help needed - Solex ADDHE (Alpina?) Author: foggyjames : member since May, 2005 : 1 post Posted on: 2005-05-18 20:24:10

Hi there, and greetings from a UK Volvo enthusiast in need of some assistance! I've just posted this on another 2002 board, so my apologies if you see this twice!

I drive a Volvo 360, and I've just fitted an 'R-Sport' (Volvo's tuning division in the 80s) tuning pack, consisting of a pair of Solex ADDHE C40 carbs (Solex's version of the Weber DCOE / Dellorto DHLA), a hot cam, and a sports exhaust system (although I don't have the latter - presumably long since rusted away!). Only 100 of these kits were ever made, and only a handful survive in the Volvo community today - of which I have two! Needless to say, expertise amongst Volvo people on these kits is almost non-existant. I believe that these carbs were fitted to the Alpina version of the BMW 2002 (as well as the Citroen AX Sport and BX Sport, and some Alfas), so I'm now doing the rounds of the various forums in search of information.

I've got a fair bit of information courtesy of an original Volvo fitting guide (which I'd be more than willing to post here), but I've got a few questions which relate to twin carbs in general as much as these specific models.

Basically, my carbs need rejetting. I have a friend who works at a long established and well known UK tuning firm, and I'm waiting for my new insurance policy (covering the modifications) to kick in before I head down there. However, it's a fair old drive (especially with the current fuel consumption) if it turns out that something is wrong which can't be fixed on the spot. There is also a risk of incorrectly drilling the jets, if we're over-compensating for another fault. In other words, I want to make sure that (as far as I can tell) the carb setup is A1 other than the jetting before I head off to have it tuned. The jets are way lean, but I'm compensating using the cold-start enrichment circuit these carbs have. On the move, it works well.

And so I get to the actual question / problem.

Basically, the car currently idles at 3000-3500rpm. It will also quite happily hold 40mph in 4th gear. It's as if the throttle is held partly open. As I see it there are a number of possible causes...

1) The throttle IS partly open.

# However, the idle speed screw is fully wound out (to beyond the point at which the throttle plates hit the sides of the barrels), and the throttle plates *appear* to be forming a good seal. So this looks unlikely.

2) The cold-start enrichment circuit (constantly activated, see above) is flowing more air, as well as extra fuel.

# Could well be this, but almost impossible to tell. The revs do indeed drop to 'normal' with the choke fully in, but the car is also running hopelessly lean at this point, so the rev-drop might simply be due to this.

3) The mixture screws are wound so far in (lean) that they're almost cutting off the fuel supply, acting simply as air valves - richened up by the enrichment circuit.

#Unlikely, simply because (as I understand it) this isn't how they work, however it was suggested by a knowledgable person. I only heard this today, so haven't had chance to try it yet.

4) There is a vacuum leak (I've already fixed one major one), being compensated for by the cold-start enrichment circuit, effectively acting as a slightly open throttle.

#Quite possible, to be honest. I'll have to have a tinker with a can of carb cleaner to listen for the evidence of leaks.

You may notice a recurring cold-start enrichment theme here! I know it's only a plaster on a gaping wound, but it means the car is at least drivable.

Any advice, guidance...anything, welcomed!

cheers,

James

• Twin carb help needed - Solex ADDHE (Alpina?) - foggyjames 2005-05-18 20:24:10 (7924 views)