IDLE MIXTURE ADJUSTMENT ON THE STROMBERG 175 CD-2

[MichaelDesna]

Could you gents please set me straight on how to adjust the idle mixture on the Stromberg 175 CD-2 Carburetors, if it can be done at all ? I've read that they're set at the factory, but there is a trim adjustment screw on the right side, but which way do you turn it to make the mixture lean ? The car is finally running after sitting for 6 years and I adjusted the slow idle running speed to 650 and it's running pretty smooth. But it's belching out thick, black, sooty smoke. Thanks, Mike
P.S. It's an automatic and one book I have says to set the idle speed at 500 and another says 650.

[johnetype]

I would suggest you follow the procedures listed here for erratic or poor idling:

https://www.dropbox.com/s/565y4hmfv1l7e ... l.pdf?dl=1

You unscrew (counter clockwise) the idle trim screw to make the mixture slightly leaner but if you've got " thick, black sooty smoke" that suggests a more serious problem which fiddling with the idle trim screw won't solve. Have you checked/replaced the diaphragms?

Automatic idle speed is 650 rpm with the selector in Neutral.

[MichaelDesna]

Thanks a lot for that, John. I've been looking for that manual and couldn't find it. -Mike

[max-it-out]

Check out the Jaglovers forum . Cars with the Strombergs fitted are much more common Stateside and you will find enough info. to fill a large book on all aspects of that carb set-up .
Basically , the Strom. 175 CD 2 was fitted to cope with the emissions regulations and was designed to be set-up at the factory and not tampered with by owners , so adjustment of the mixture is not possible . However ...there are ways of getting around this -

1 ) fit a different needle . Early `68 cars used the B1E which was quite rich at higher air flows . Later cars used the B1AR needle .Others needles are available such as the B1AF ( original fitment for the TR6 ) which will give a quite lean mixture , and the B2Y which is a bit richer .

2)Fit adjustable needles or jets . Available from Joe Curto in the US and others .

The idle screw on the side of the carb seems to be there to compensate for new engines which may not idle as required with the stock setting . As this is just designed for idle speed . it probably won`t work very well as a general mixture adjuster , but I`m not 100 % sure on this .

[MichaelDesna]

Thanks for that info, Mark, but I think that the problem may be something that John was talking about and I want to try to check the diaphragms first before changing the needles out, both of which I know nothing about at the moment.
John, would it say in the manual where the diaphragms are and how to check and replace them ? This car is new to me and I'm learning things on the fly here ! That would make sense that there is something else serious going on causing the thick, black, sooty smoke because when I turned the idle mixture trim screw nothing happened. -Regards, Mike

[PeterCrespin]

Sounds like stuck floats or needle valves giving flooding, assuming you have changed to a higher pressure fuel pump. Are both tailpipes equally black? If you have the ignition on but the engine not running do the carbs drip fuel? Assuming the car ran until it was laid up, it's unlikely to be float height trouble.

The diaphragms are the rubber things you see when you undo the four screws and lift the top from each carb. They should not be split, although I think that would cause weakness not soot.

If you're asking questions like what/where the diaphragms are, you do need to read and study the basics before trying anything else IMO, otherwise you might struggle to understand the answers you get. Good luck.

[MichaelDesna]

Yes, Peter. I'm not going to fiddle with the carbs any more until I learn more about them. When I bought the car 6 cars ago from a local person who had it just sitting in his yard with no hopes of restoring it, it took forever to start and ran very choppy. I brought it to a local restorer who worked on the body only but then went out of business this year so I took the car home. It turned over but wouldn't start and I heard no "ticking" coming from the fuel pump. I installed an electronic fuel pump, changed the spark plugs, oil and filter, changed all the fuel filters (the one in the sump had broken up and the sump was filled with debris), and when I turned the key it started right up. But it seems like it is running very rich and like I said blowing out black soot and smoke. I'm going to read about what you suggested.
Thank you ! -Mike