1950s 55 Eldorado Carbs wrong way round and choke adjustment.

[Lockhouse]

Hi,

I have a conundrum on my '55 Eldo.

I believe the twin Rochester carbs have been refitted back to front when the car was restored many years ago. The car is non A\C.

The front carb is tagged 7007942 and the rear 7007240. The service manual says this is the wrong way round.    Both have the A5 designator so are late '55.

So I have some questions:

I took off the batwing. The front carb choke flap appears not be be fixed and just flaps around. The rear choke flap works correctly i.e. is partially open when cold and then fully open when warm and does not move when touched. Both carbs have the heat pipe on the right connected correctly to the choke body. The front carb has no retaining screw (i think this may be the fast idle adjustment screw) for the choke mechanism itself which on the rear carb is what stops the choke flap being able to move. I attach a photo of my front carb linkage. Is this correct for a front carb?

In the parts book (not the service manual) it says that both carbs are 7007240 and that you remove the fast idle screw from the BACK carb.

Does anyone know the difference between a Rochester 7007942 and 7007240 and does it make a material difference if they are the wrong way round?

If someone got the tags wrong, is there another way to check the numbers?

If one of the choke flaps is supposed to flap around, why are they BOTH connected to the automatic choke warm air tube?

The car runs fine and has done for the past three years but there's always been something that's "not quite right" with the fuelling. I came across this one whilst investigating possible causes.

Thanks for any light you can shed on this.

Best regards,

Andy

[Lexi]

Andy, I can't answer most of your questions as I have never worked on, or studied '55 & '56 dual quad carburetor systems on Cadillac Eldorados. I did consult my 1956/1957 United Service Motors Rochester Carburetor Service Manual, which also does cover 1955. It identified the 7007240 as the front carb, and the 7007942 as the rear "Std only", (meaning non-AC). The rear AC equipped car was fitted with a 7007241 carb. This manual did say that (quote), "Adjustment procedures are the same as listed in Bulletin 9-C-205 for Rochester Carburetors 7007970 and 7007971, with 2 exceptions", (see attached image for more details). I could be wrong, but there seems to be some differences in the throttle body assemblies as there are different part numbers listed, for various 1955 carbs. Hope some of this helps. Clay/Lexi

[Lockhouse]

Thanks Clay, actually quite useful.

That does bear out that my carbs are reversed - I don't have a fast idle screw on the front, only on the back and the page you added says it should be on the front.

If I can get my other questions cleared up, then I will be able to make a decision as to whether to open that particular can of worms or just put up with the niggles.

If there's a specific difference to the inlet manifold that optimises flow from the front carb into the engine that would make it a necessity to change.

I do know of one or two other Eldos in the UK - I will see if I can go and see one next time I'm in their area.

Added: I friend has sent me a video - the fast idle adjustment screw is on his front carb so mine is definitely wrong.

A journey of discovery starts with but a single step!