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CD150 Stromberg carb' needle part# or profile

Posted: Fri Apr 27, 2012 11:14 am
by Neil Spooner
Hi Guys,
I have recently fitted a "new old stock" CD150 carb' to replace the worn out previous unit which is fitted to a Tipsy Nipper.
The old CD150 is of the fixed needle type with needle 6P, the later carb' the floating needle type has a B5EP needle which is a different profile. The Stromberg parts suppliers I have spoken to say it is not possible to cross reference the early and late needles (I would have thought it relatively easy).
Is there anyone out there who can tell me what needle they are using in a VW1834cc Prop' is a Lodge 56x34.
The needle I need measures at 1/4 length positions:

Posted: Sat Apr 28, 2012 6:53 pm
by Tom Sheppard
Burlen Carburettor Services near Old Sarum should be able to supply what you need.

Posted: Sun Apr 29, 2012 9:25 am
by Chris Martyr
Hi Neil,
I fly behind an 1834cc VW with a Chris Lodge 57" x 32" prop.
About ten years ago when I was building the engine, I had a similar problem, as I was unsure which needle to use on my Stromberg CD150.
Barry Smith's advice was that no standard needle was completely compatible with a VW, and the best way to get the mixture correct was using the following trial and error method :
It will be probably running too lean anyway, so start the engine with full choke , as it warms up , try decreasing the amount of choke, then remove the piston and polish the needle with a few strokes of fine Wet n Dry , then stick it back together and run it . Keep doing this until it runs without any choke at all . Once you get into the 'ball-park area' it may need a little fine tuning. Again,,a bit trial and error, but it worked superbly on my VW.
I guess yours is the type that uses that pain in the neck special tool that you stick in the top of the dashpot is it? That's probably just as much trial and error as the method described above .
I would be intersted to know how it goes. Cheers , Chris

Posted: Sun Apr 29, 2012 3:16 pm
by Neil Spooner
Thank you Gents, the chap at Burlen is away till tomorrow, so will call him then.
The engine runs well at all throttle openings with no hesitation on application of sudden full throttle from idle, and is reaching about 3000 rpm at full throttle, so the current needle is ok on the ground, but I have yet to airtest the engine. The 6P needle came from the late David Mickleburghs engine, and I don't doubt he did the research and development to find the correct needle. Finding the equivalent needle to this I think is the "easy" way ahead, but of course it will still need checking.
Yes, this carb' is the one that adjusts from the top, but I find that is much easier to access on this installation than the adjuster at the bottom.
Chris, is yours the fixed needle or the sprung one? If the sprung one do you know which needle you are using, or is it modified?

Posted: Tue May 01, 2012 4:02 pm
by Chris Martyr
Hi Neil,
Unfortunately, my carb is the old fixed needle type , so giving you it's needle ident. wouldn't help you very much mate . Also, it has been modified, by me , using the fine wet n dry technique .

If you are achieving 3,000RPM with static ground runs, and no flat spots at all stations in-between, then it sounds like the Nipper could be ready to slip those surly bonds yet again . Onwards & upwards, Rgds Chris

Posted: Wed May 02, 2012 8:01 am
by Neil Spooner
Thanks for your help Chris,

Re: CD150 Stromberg carb' needle part# or profile

Posted: Sun Aug 26, 2012 10:15 am
by Greg Shepherd
On the same topic, can anybody help? I see from previous comments that I am not the first person to have problems finding the correct needle for my Stromberg CD150 Carb (New Old Stock).

My FRED G-BWAP has an 1834cc conversion and the needle is a B5CL. The engine starts readily and ticks over at 800rpm. As I open the throttle the revs climb nicely up to about 2300/2500 and then hit a rough patch. If I gently push forward the revs climb to 3000/3050 and run smoothly. The engine has been completely overhauled, as have both mags, it has just got to be the carb. Can anybody please suggest the correct needle or how I can overcome this, I would be very grateful?

Re: CD150 Stromberg carb' needle part# or profile

Posted: Sun Aug 26, 2012 11:37 am
by Neil Spooner
Hi Greg,
The VW engine is a bit quirky about inlet manifold and exhaust design. Do you have 4 open stacks, or do you have some other ex' system. The engine fires both cylinders on the same side consecutively, and both ex' and inlet manifolds can suffer due to the pressure pulses. A picture of your setup would be interesting to see. (I have made and tested quite a few, some just don't work)
The needle profile I would suggest is a B5CE from Burlen Fuel Systems:
(Very helpful chap called Stan works there)
Does the engine "stumble" on rapid opening of the throttle from idle?
I would highly recommend fitting a vacuum gauge to the inlet manifold to see what is going on with the engine. If the engine/prop' combination and set-up of the engine is correct you should be able to cruise with about 5" of manifold vacuum. If you have less than that you are "labouring" the engine and will suffer all sorts of short and long term problems.
Good luck,

Re: CD150 Stromberg carb' needle part# or profile

Posted: Tue Aug 28, 2012 2:30 pm
by Greg Shepherd
Hello Neil

Firstly many thanks for such a speedy reply to my call for help. I have done as you suggested and ordered a B5CE needle today from Burlen.

G-BWAP has not actually flown yet due to a number of small problems and I have to admit I have not tried rapid opening of the throttle from idle, but will experiment more when the new needle arrives. I have attached one or two pictures which may be of interest.

Thanks again. Safe flying.

Re: CD150 Stromberg carb' needle part# or profile

Posted: Tue Aug 28, 2012 8:57 pm
by Neil Spooner
Hi Greg,
Thanks for the photos, it looks like a very nice job you are doing.
A couple of thoughts:
How fuel resistant are the rubber pipes you are using? If you are using unleaded (and you should for engine longevity provided you have the correct CR.) I would suggest putting a small measured piece of one in a jar of mogas and waiting a week and remeasuring it to check for deterioration and swelling.
Try taking off the carb' heat box from the front of the carb' and running it without, or if possible with a trumpet of some sort.
The VW/stromberg carb' combination is a carb' ice magnet. You need to be absolutely sure you get enough temp' increase with carb' heat applied. Use a thermocouple in the intake, you are looking for about +30degC increase at cruise power. I see you have the oil "cooler" block on the carb' outlet flange. For that to work in reducing carb' ice it needs to be bolted directly to the carb' without a gasket. (The gasket will provide a heat barrier) It may be possible to use an O ring in a machined groove on the cooler face.
I am a bit rushed at the moment, but will try to give it some more thought.