I took the car for MOT today and it failed on hydrocarbons.
Engine is a Vulcan crossflow with 40 DCOE Webbers.
I have no experience of theses carbs so quqestion is ,which screw will bring the reading down.
Thanks in advance. Kipper.

Try to find out which cylinder is giving problems....
My motor was crap to begin with on HC but I'm pretty sure one of the cylinders wasn't firing. Hence unburnt petrol going straight through the engine... Certainly taking off the spark lead made no difference to the sound... Changing the spark plugs seemed to sort things out and after that (and a colortune tune-up) my HCs had come down nicely...

sorry, i don't know, but i was wondering about the vulcan crossflow...

I've got a vulcan V6, I'd never heard of Ford vulcan engines before. where is it from?

http://www.vulcanengines.com/

ah, that type of vulcan. vulcan engineering... no, mine ain't one of them

Have fitted new plugs and it seems all cylinders are firing but plugs come out black as soot , the car goes like hell when I floor it but they tested it at 1500 rpm.

ok, i beleive the mixture screw is the screw with the spring round it, sits just above the butterflies bolted to the manifold. as far as i can tell from a black and white drawing in my weber carb book, they are brass screws with knurled edges.

my experiance in setting up carbs is almost nil so far, but i guess the mixture could be set too rich?

Thanks for that blakep82, does it say which way to turn it to weaken the mixture?
Regards Kipper.

i couldn't actually find anything about adjusting the mixture, but seeing as its a screw, if you screw it in it reduces the size of the fuel channel, and makes it wider if you unscrew it. i guess screwing it in weakens the fuel in the mix.

photo of the page coming in a sec...

Description

Description

[Edited on 23/3/07 by blakep82]

Too lean on idle. Richen it up, and the CO will rise, and the HC will drop.

It's not as simple as turning a screw - that will only adjust your idle mixture at about 800 rpm. You probably need to change jets. See attached site for really good basics. All bits are available from Burton
http://members.aol.com/dvandrews/webers.htm
Sorry - I've never worked out how topaste a proper link

Jeff

Do you have a leak in your exhaust?

what age plate are you on? all non cat tests are done at idle so why are they testing yours at 1500rpm?

What age is the engine ? may only need visible smoke test?

Hi Dennis which garage did you go to for the mot ? i have to get my indy mot soon
Graham

Hi all ,,, engine is a crossflow ford, all the paperwork is at my place of work so I cant tell the age until tomorrow.
I was under the impession that it should only have a visible smoke test. I will have to ask about that when I take it back for retest.
Jacko, the garage is near Selby where I work.
Thanks to all who replied to my question, I have taken on board you comments and will try to sort it tomorrow.
Regards Kipper.,,,,,,,,,,,,AKA Denis.

Simplest way of thinking is: HC means missfire. Anytime there is HC it means that you are getting improper burn for some reason.
High CO means too rich, low CO too lean.
So, if your CO is low as well, you are probably getting a lean missfire.
If you give us numbers we can probably help you more. Your numbers, the limits, and average readings if you can.

If it's on a Q plate defo only vis smoke test. If on an age related plate then depend on the age of the engine & when registered - given that it's a Kent I'd have thought most likely you shold have vis smoke test only. That said would expect engine to passon HC's at 2000 rpm unless it's not running right or not set up correctly