I am considering buying a Gunsons Gastester to set up the Solex carb on my 1972 BMW 2000 Touring, and the twin SU's on my '65 Amazon and whatever it is on my Capri 280. I have two questions:
a. Is there a standard CO figure that you always try to achieve, or does it vary per car. If the latter, where do you obtain that figure; I don't believe I have seen it in my Haines manuals.
b. How will I make sure the mixture on the SU's is the same for each carb; I have the Gunsons Carbalancer but that I use to set the throttle response...right?
You do know it will only work at idle? Unless you had access to a rolling road? Ie, it can't be used on the move. And even then the probe is only designed for a slow gas flow.
Also, the entire exhaust has to be in perfect condition to get an accurate result.
The easiest way is with your ears. Get a disposable - or cheap - stethoscope from a medical suppliers for a couple of quid. Or you could just use some tube. That sets the flow.
To check the mixture at idle, you lift the piston a fraction - say a couple of mm. Most have got a pin to allow this. If the mixture is weak, the engine will slow down. Rich, it will speed up. Correct and it won't change - or may speed up slightly then come back to the same speed.
Something of a piece of crap. S/H commercial is much better, although more expensive. The older analogue version is a bit more readable.
They're useful for detecting high CO due to gross oilburning, or for adjusting the idle mixture on an engine where getting the idle right is simple and all you need to do. In practice though any car worth bothering about is more complex than this, and the Gunson gas meter just doesn't tell you enough.
The ubiquitous Colourtune plug, or rather a pair of them (four for V8's like Rovers with twin carbs and a cross-coupled inlet manifold).
They're not the greatest device for measuring overall CO to MOT standards. But when it's a question of doing comparative measures across cylinders, such as multi-carb setups, then there's nothing to beat them.
A useful idea, but I've always found this to be rather poorly made, inconvenient to use and of little real benefit. Much better is the Crypton Synchro-Check. This is a swinging flap meter with a direct reading scale. You don't need to fix that vertical tube in place or deal with the hose. They haven't been made in years, but they're around on eBay and the autojumble circuit.
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