Adjusting Stromberg idle mixture 4.2, 2 + 2...

[MichaelDesna]

Hi Guys,
Does anyone have any advice on how to adjust the idle mixture on a 1971, Series 2, 4.2, 2 + 2 ? Is it possible to do it without having an exhaust analyzer ? Here is a picture of one of the two carburetors below and my finger where an adjusting screw is Thanks ! -Mike

[mgcjag]

Have a look at this thread from post 19 on viewtopic.php?f=2&t=15153&hilit=Stromberg+mixture
Also in the Knowledge base section there are a few articals on Strombergs

[MichaelDesna]

Thanks, Steve. I'll look them up. I'm still a newbie on here so I don't know yet where everything is. The same goes with the car !

[max-it-out]

Are you sure that is the mixture screw ? Mine has a screw in roughly the same position that is just an adjustable stop for the choke lever .

[Bob.]

Hi Mike,
Plenty of reading in the links Steve has given you. As suggested, the screw you are pointing at is the "summer" or "winter" selector for the choke, so nothing to do with normal running.
If the carbs are original, there is a limited amount of mixture adjustment available by removing the air piston rod (unscrew the black knob in the middle of your picture) and inserting a special tool to wind the fuel needle up or down in the fixed jet. The tool is readily available and is shown here http://zenithcarb.co.uk/carb-adjusting-tool.html.
Hope this helps,
Bob

[johnetype]

Bob, maybe adjustable on a UK Series 3 Stromberg but on a US Series 2 car the jet is non adjustable and you can't wind it up or down with the tool you're suggesting.

Mike, the only adjustment related to idle mixture is the "idle trim screw" (which is not the one you're pointing to). If you read the Emissions Controls Section of the Jaguar Service Manual for your car which is in the Knowledge Section on here, that tells you what adjustments you can make and describes the function of the idle trim screw.

[Bob.]

So in that case the only option to get mixture adjustment through the range on the version fitted to S2 is to get Joe Curto to modify them to take the old style adjustable jet/ fixed needle set up. ISTR Joe is in New York.

[Tbob]

You dont need to send your carb to Joe. The adjustable jet is a screw-in replacement for the fixed jet. Swaps out and sets up in just a few hours.

I can vouch for the quality and performance of the mod. Really woke up my S2.

Note: I just looked and it seems Joe may be “between websites”. Joecurto.com is now pointed at a place called British Superior. His email address is still listed on the page, though. I suggest you contact him directly via joecurto@aol.com

[MichaelDesna]

Thanks for all that good info, guys. I did some research and the screw I'm pointing to in the picture IS the choke adjustment screw. There is a screw for adjusting the mixture on the other side of the carbs but I can't keep the engine running long enough now to do that because the transmission oil cooler in the radiator just sprung a major leak and I got to find out how to deal with that first.