Stromberg's

[kerryblu]

Hi all,
In the wsm section L page 46 part no. 28, is missing on my carbs,what do these screwss do ? My car is u.k. model,cause on page 38it dose not show these screws.Could I blank the holes of with a bolt, or should I tapper the end as it shows in wsm? Also dose the choke work of the 2 carbs or just the front one?


thanks for any info on this subject.

Gerald.


70 dhc S4 oew.

[69S4]

On my carbs something is blocking the hole that part 28 goes into. From the top there's about 5mm of empty hole and then (probably) part 27, an anti-fiddle plug. In the Haynes Stromberg manual it calls 28 a leak balancing screw and it plugs a hole that goes between the choke bore and the area underneath the diaphragm. The tapered part is there because the hole isn't plugged completely, it allows a small, measured, amount of leakage to allow for manufacturing tolerances between the air valve and the main casting, the idea being to even up the air leaks between pairs of carbs. If you've got nothing at all in that hole there must be a huge air leak (although if both carbs were like this at least they'd be balanced )

If you need to plug the hole, probably your best bet is to plug it completely as without some sort of flow bench arrangement you'll never work out exactly how much leakage to allow. It might not be a bad idea to give Burlen a call though and see what they have to say. I've always found their tech people helpful.

Re the choke mechanism, there should be choke assemblies on both carbs. Originally the cable looped from one to the other in a sort of "push-me pull-you" arrangement that opened both at the same time but I found the amount of force needed to operate the knob when it was like this threatened to pull the dash off of its mounts. Last time I asked you could still buy the cables.

[kerryblu]

Hi again,
does anybody know the length of part 28 plus the length of the taper and how much it is turned down to at the bottom end. It looks like a flat screwdriver cut-out for turning the screw into the carb. Or does anyone have any stromberg screws for sale?
Many thanks
Gerald
S4 70 DHC OEW

[Frank Howard]

...there should be choke assemblies on both carbs.

Stuart,

This is the first time I have ever heard of this. I have never seen a Stormberg Elan with two chokes. Even my Stromberg Europa has a single choke.

[oldelanman]

...there should be choke assemblies on both carbs.

Stuart,

This is the first time I have ever heard of this. I have never seen a Stormberg Elan with two chokes. Even my Stromberg Europa has a single choke.

The federal emission set-up had a single choke on the front carb only, eurpoean cars have always had chokes on both carbs. I suspect that most federal cars have long since had the emission bits removed but probably never had the rear choke fitted to complete the conversion to european spec.

Regards,

[69S4]

Hi again,
does anybody know the length of part 28 plus the length of the taper and how much it is turned down to at the bottom end. It looks like a flat screwdriver cut-out for turning the screw into the carb. Or does anyone have any stromberg screws for sale?
Many thanks
Gerald
S4 70 DHC OEW

Can't help with that unfortunately, mine have never been out. My carbs are on the car so I can't see how they look from inside the casting but someone here must have some Strombergs sitting around on a bench and could have a look. In the first instance though you ought to get in touch with http://www.burlen.co.uk/. They're the manufacturers so I would have thought they'd at least know about them.

...there should be choke assemblies on both carbs.

Stuart,

This is the first time I have ever heard of this. I have never seen a Stormberg Elan with two chokes. Even my Stromberg Europa has a single choke.

I'd always assumed they all had two chokes! If you live in a warm sunny climate (like all of the USA ) you could get by with one choke and here in the summer I only use one when starting. But for the rest of the year the car can be a bit cold blooded for a mile of two without the second choke. At the moment I've got mine set up so the rear one does mixture and idle speed but the front one just does mixture so I can enrich it without increasing the tickover - easier when going out of my road straight into a traffic jam in the morning.

[Frank Howard]

If you live in a warm sunny climate (like all of the USA ) you could get by with one choke...

Stuart,

Funny you should mention that on the day of our first winter snow storm. If they're putting down salt, that's the end of driving the Elan until spring. I guess I really don't need a second choke

[Esprit2]

In the wsm section L page 46 part no. 28, is missing on my carbs,what do these screwss do ? My car is u.k. model,cause on page 38it dose not show these screws.Could I blank the holes of with a bolt, or should I tapper the end as it shows in wsm? Also dose the choke work of the 2 carbs or just the front one?

Gerald,

Compare the parts illustration on pg 46 with the similar illustration on page 38. Note that the ZS carb version discussed in the earlier Section L.15 doesn't include the Balancing Screw, while the ZS version in the subsequent Section L.17. - Zenith Stromberg Carburettor (Exhaust Emissions) does. Which model ZS is in your car, and are you looking for something your carb doesn't have?

If you have the Haynes Manual, go to page 39 for an explanation of the Leak Balancing Screw. It's a lot like the Air Bleed Screws on Dellorto DHLAs. The Balancing Screws were added to the "emissions" CDSE and CD-2SE, and were also present on the following CDST and CDSET models. The screws were not present on the earlier, pre-emissions CD, CDS and CD-2S models.

Quoting the Haynes Manual:
"As explained in Part 1, Chapter 2, the air valve is a close fit in its bore in the body. The very small annular clearance around the air valve permits a leak between the ambient pressure region below the diaphragm and the low pressure region in the choke bore (ie, main carb throat - tim) and mixing chamber, which lowers the depression. It is essential that all carburettors for a specific application are matched exactly in respect of flow. To compensate for the very small variations in component sizes (air valve diameter and body bore diameter) due to manufacturing tolerances, and adjustable screw is incorporated to provide an additional air bleed between these two regions. By adjustment of this screw the total leak may be held to a controlled value, irrespective of the 'unknown' spurious leak. Once the screw is set, on initial build, it must not be altered and to prevent tampering, the bore into which it fits is sealed with a plug. The body, air valve and cover become a matched set and neither part may be replaced independently of the other. The suction chamber cover is wired to the body, and may only be removed after the seal has been broken, thus reveling that the unit has been tampered with."
End Quote

Making a Balancing Screw would be about like making a Weber/ Dellorto Idle Mixture Screw. It's a precision part and simply carving a point on the end of a bolt won't suffice. But if you had an accurate part drawing (I don't) or an original screw to copy, then a skilled machinist could turn one for you.

When Stuart Holding,

(Snip)... In the Haynes Stromberg manual it calls 28 a leak balancing screw and it plugs a hole that goes between the choke bore and the area underneath the diaphragm. (Snip)...

The "choke bore" he referred to is the main carburetor throat, not the cold start enrichment device which is often incorrectly referred to as a choke. In this case, "choke bore" is used similar to the way Weber & Dellorto carbs are said to have interchangeable "chokes"... ie, primary venturis. The Balance Screw is in a passage connecting the main carb throat (choke) and the ambient pressure region below the diaphragm.

Re-balancing carbs in which the factory setting has been disturbed will require access to a manometer and, ideally, a flow bench. Without the flow bench, you could balance the carbs on a running engine, but variance may creep into the setting due to differences in the running strength of cylinders 1-2 and 3-4. But that would still be better than an open hole, or one that's just tightly plugged.

The factory would have balanced a carb against a standard. However, lacking that standard, if you balance a carb-set on a running engine, the Balance Screw on the carb with the weaker depression should be screwed in and securely closed. Then the screw on the companion carb(s) with a stronger depression should be opened as required to weaken the stronger depression until it matches the master carb.

Regards,
Tim Engel
Lotus Owners Oftha North (and yes, the salt trucks went out today... bummer)

[kerryblu]

Hi all,
Just brought the front carb indoors to have a good look at it , its a 175 CD-2.Now with better light, and the MRS's glasses, looking down the 1'' depth hole there is 1/2 an inch of UNF thread then the bore is smooth as is the base of the hole, it looks like there is no holes coming in or going out, other than the main bore hole. So I hope I don't need No 28 after all. Will find out when I get her going in the next month. If you still got any re-assurance always greatful.


Gerald
S4 70 dhc oew.

[Esprit2]

Press your lips tightly around the hole and blow. Does air flow, or not?

Regards,
Tim Engel