Lagondaforum

Subject: Help identifying SU carbs

---

I was hoping someone in this forum could help me confirm if the two sets of SU carbs I have did in fact come from a Lagona. I have two sets of SU carbs ...
1. SU Long Neck Thermo Type (1.1/2 inch through 5.125 inch body (4031)
2. SU Short Neck Thermo Type (1.1/2 inch throat, 4.843 inch body (446)
I believe they come from a Lagona but need confirmation as I want to identify the exact model number for spares. They are similar to the Aston DB2 and DB2/4 carbs but not identical. Photos attached.

Thumbnails of attached images:

Subject: Re: Help identifying SU carbs

---

Your second ones with short neck look similar to my DB 3ltr Lagonda ones but there are differences: here you see mine
http://lagondaforum.com/attachments.php?action=attachment&id=308
There was no electromagnetic enrichment device mounted on the DB Lagonda but it has a choke pulling down the main jets. This is linked between both carburettors. Length in suction direction is 5.5"
Why do you think they are from a Lagonda?

Subject: Re: Help identifying SU carbs

---

Thanks Peter.
Im restoring a 1954 Aston DB2/4Mk1. However it never had its 3.0 litre unit. I managed to source a motor in the UK, but its a 2.6 Litre unit. LB6/49/48, which I believe was from a 1949 2.6 Litre Lagonda. I think the one set of carbs came from there, but need to determine the exact SU part number. I'm not sure where the other's came from. The two sets I have are pretty much the same. Neither have the choke mechanism, both have the thermo relay. The long necked ones have a longer body and the vents are in a slightly different place. Other than that there is not much difference between them except for the different length bodies. They may well have come from and Aston, but the engine number suggests a Lagonda, and since they are pretty much the same, I have assumed they both came from a Lagonda. In addition the Aston carbs had a little spur on the neck of the dash pots. And most astons had a choke control.

Subject: Re: Help identifying SU carbs

---

I have an SU carburetter workshop manual, & that states that the brass suction piston was replaced by a thin-walled aluminium one in 1950 (but the brass one can be replaced by an aluminium one with spring). Up to 1939 the pistons were thick-walled aluminium or zinc.
This might at least help date the carburetters...certainly the longer neck ones are earlier, & I'm fairly certain the shorter neck ones are post 1950.
Laurence

Subject: Re: Help identifying SU carbs

---

Simon,

I always thought the Lagonda engines end up in the Astons but now they are missing there too..

I only can add another photo from my Lagonda DB 3ltr carbs from above (silencer removed). The Aston should look the same, it simply had no silencer but the little air filters instead.
I added a pull back spring on an arm in the middle of the two carbs because they did not go fully back in idle, maybe need a complete refurbishment later.

Burlen has the right parts for the Lagonda 3ltr. carbs
http://sucarb.co.uk/CarbEssentials.aspx?ProductId=10112
you can compare to the ones they supply for the Aston DB2
http://sucarb.co.uk/CarbEssentials.aspx?ProductId=10076
much the same but e.g. different needle

your pair with long necks are certainly not from a postwar Lagonda or Aston

Peter

Thumbnails of attached images:

Subject: Re: Help identifying SU carbs

---

Thank you Lawrence and Peter.
"the brass suction piston was replaced by a thin-walled aluminium one in 1950 (but the brass one can be replaced by an aluminium one with spring"
The two sets I have both have brass pistons and this seems to fit with 1949 time frame from the engine number. I note from your photo Peter that yours are pretty similar to the Aston Carbs with the little spur on the dash pots. The long neck ones, could potentially come from the same time period (late 40's) but from a different car. Thanks for all your help, I have a little more investigation to do. .
If anyone else on the forum could post pics of their late 40's 2.6 litre lagonda carbs it would be greatly appreciated.

PS. Thanks for the tip on the pull back spring.