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Stromberg CD 150s revisited

I just got off the phone with Joe Curto. He has the needles and will put them in the mail. A very helpful guy (Bob) at Apple Hydraulics gave me the Curto lead and gave me a bunch of tips. Apple hydraulics makes the needles but said there is not enough interest in 6Js for a new run. Bob gave me Checking float levels/ raising float levels, air leak stuff, but he also said to file a side flat as an approach. Apparently they did a lot of this stuff when fine tuning race stuff. He said it would be tough to mess up the filing job. Either way 5Ms are available all day— I have two sets here.

My old parts set of cd150s has the neutral colored springs.

I will let you know how things go— either way , I am cruising for a carb rebuild In the near future.
Thanks all
Question: Not sure how much latitude there is but if I did not set the needle flush with the piston, but raises it higher in the piston would that get more fuel to the carb?

How is this richening going to effect my dieseling?
Raising the needle should make the mid-range somewhat richer, but I doubt that it will have much affect on AFR at idle or top end.

True diesel ignition typically results from a combination of too much compression and / or not enough octane rating and I doubt that AFR will make much difference.

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Series V idle speed is 900 to 950.

LOL - Beat me to it.

A lower idle speed would go a long way to prevent engine run-on at shut down. Makes me wonder why Rootes thought idle speed needed to be that high. Was it because the higher revs covered some ill of the CD150 which would be a driving issue at a lower idle speed?

Just a thought,

Taken from WSM 145:

Tripped over this 2003 thread about how to choose needles for CD and SU carbs. I just skimmed the info and thought to post on this thread before I lost it in limbo.

It might be of interest to a few.

After seeking a source for metering needles, it seems choosing a needle might be easier than acquiring the chosen units.

Have fun,

I read through the link husky provided and had to laugh. I was in the jungle in seconds—-. I am one to more likely follow Mike’s advice than sort through the charts and interpret acronyms. Summary of Mike’s advice “ 6Js worked for me”.
I will however play with some filing for curiosity sake.
For those following this thread— I sprayed all around my carbs and did not get any changes. So I will be working off the notion that I am not sucking in air to lean my carbs.
update — for those still interested.

Still waiting on the 6Js, but I did a filing experiment. It was a disaster for me. I gave up after about two hours of fiddling ( hard to start- couldn’t idle- a mess) around. This is an adaptation for someone who knows what they are doing and that was clearly not me.
The odd bit is that my car seems to run with a bit more enthusiasm and I was able to turn the jets in some after the return to 5m with fresh adjustments. I lost track of how many turns back in— I will check and while I was Dieseling some during my latest adjusting, my last shut down after about a six mile toodle, my car shut down cleanly - no run on. More testing today on the running on.
Butchered 5Ms for sale ( haha) lightly used!!
Just a question of curiosity.

Did you modify the original needles, or the spares?

Please keep us posted,
M5 is the standard needle and that is what I tried to modify. Mike suggested the 6J and they have not yet arrived.
I got the 6Js from Joe Curto and installed them this morning.
I started with my jets 3 turns out. After playing with the throttle speed and jet adjustment, I ended up at approx 3 3/4 turns out. I did not bother to start with the jet leveling process with the bushing— I just took the jet height from where I had left it—anyone think I should have started at the leveling process before I started looking for a proper jet height?

My idle is about 900 and for the last two testing rides, there was no dieseling. Plenty of pep and nice gas pedal reaction.

1) Is it alright to be 3 3/4 turns out? Car running good— no popping on deceleration or diesaling. Not enough milage ( about 20) to get a good reading of the spark plugs.
2) In the promo piece from Joe that came with my 6Js, there was a reference to many, many needles. While I realize that most of these needles are for carbs that are not stromberg cd 150s,I wondered about more options. How many needles were made that a stromberg cd150 can use given that 5Ms were the standard and not the best set up for my car. So far, I am pretty pleased with my results, but I am curious about options and potential results for general knowledge sake.

Be well all - looking forward to your comments.
There are many other needles that will fit. But I wouldn't play around with other needles. My guess is that if you are 3-3/4 turns out with the 6J needles, then the next step is to rebuild the carbs. I would expect you will get to around 2 turns out after the carbs are rebuilt. Sounds like the car is running well which can buy you some time to decide when you want to rebuild the carbs.

I am not following your comments about jet leveling. You should centralize the jets per WSM 145 (section C, pages 57 & 58), then screw in the jets until the air valve just starts to rise, then start turning out the jets. You should also synchronize the carbs.

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Hey Mike

I was referring to wsm pg 58 section C no. 5 in the centralizing jet using fig 12 on page 57. My guess is this the equivalent of what you say “ when the air valve starts to rise” . When the air valve starts to rise or slightly before “ the top of the jet is level with its bushing”.

I assume that when a rebuild of the cd 150 takes place, the jet is replaced and the hole in which needle runs is new again and the 5M will be adequate. I need a little help here. If by changing to the 6J, I am using a narrower needle and from use the diameter of the hole in which the needle travels has gotten larger, how then does a new 5M work as intended with the new narrower jet. Not that clear -sorry—trying again— if the hole the needle travels has gotten larger due to use, why is the narrower 6J needed to allow more fuel into the mix? - with the hole now larger isn’t more gas allowed to pass around the 5M?
Maybe I am misunderstanding what the 6J is now doing that the 5M could not.

Sorry to be a bit thick here!
The needle doesn't make contact with the jet unless you have a bent needle or the jet isn't centralized. The jet diameter remains constant over time. It doesn't "wear" and grow larger over time.

The 6J needle allows more fuel to flow past it than the 5M (probably 15% more). If you rebuild the carbs, stick with the 6J needles. They will help account for the differences in fuel from the 1960s versus today. I expect you will need fewer turns out on the jet screws after a rebuild as you shouldn't have various leaks allowing extra air into the carbs resulting in a lean condition.
I did not think the needle made contact. Thanks for confirming that. I guess that also suggests that only gaskets, orings and seals need replacing in a rebuild— metal parts will all be good and reusable?

I did spray carb cleaner around the carbs as one suggested early on that I might have an air leak and my idle did not change. Once a rebuild is completed and all potential leaks are sealed off, is the only reason to keep the 6Js is the modern fuel vs 60s fuel issue? Is everyone who runs cd 150s using 6Js rather than 5Ms- the “standard”? What will be the reason for “fewer turns out” once the rebuild is complete?
I hope all the questions are not a bother— just trying to expand my understanding.
With gratitude