I want to eliminate the starting carb on my 3.8 litre engine. ( It doesn't function, is missing internal parts, apparently is not even wired correctly and LEAKS GAS !.) I am researching whether or not a float bowl (part # AUC2009) from the rear carb, can be mounted onto the front carb in place of that float bowl ( Part # AUC2088). Obvioulsy, I'm thinking of having the AUC2009 float bowl point towards the front of the car. I am concerned however whether the existing fuel line will then mate-up with this carb bowl or be hopelessly misaligned.
I am not worried about this engine starting w/o the starting carb. I have read and studied at least 15 different "threads" about the ASC and discussed its issues with Joe Cuerto here in the states, a known expert on SU carbs. I am presently inclined to attempt eliminating the ASC altogether.
I also had talked with a Mark 2 owner about 18 months ago and he stated that his ASC was "plugged off" and has had no problems with the starting or running. I am also interested in this "solution". I wonder if a brass bolt could be sourced that would simply screw into the bottom of the AUC2088 float bowl and serve as such a "plug". Or any other suggestions about how to "plug off" this ASC.
Any / all thoughts and opinions are greatly appreciated ! Thank you !
Schmitty

 

You can flip them, or in this photo, I just blocked it off.
With out checking I believe the thread is 5/16 BSF at 22 TPI.

I have a complete set of BSF taps and dies so I just made my own out of a 5/16 bolt, the brass acorn nut in BSF, I had on hand.
The carburetors have been converted to a manual choke where the main jets can be lowered and raised.
They are connected together with extended levers and a rod.
Take note they have been set up for my Bentley, not for a Jaguar, but the set up would be similar.

With the manual type chokes, you will need some sort of throttle for fast idle, or you will have to sit there with your foot on the gas until it warms up sufficiently.
I can't see how the car will start with out some sort of choke system, if you plan to totally eliminate a choke set up.

And the existing fuel line will line up, you will still be using the same top of the float bowl on the other float bowl, the dimensions are the same.
All that was done was a hole was drilled and tapped to accept the ASC on the bottom of the float bowl.

The owner whos car starts without any choke at all, more then likely has it set so rich, it starts.

 

I agree, you need starting enrichment if the carbs are set correctly for running with the engine up to temperature. I'd look at using a manual choke conversion, I believe there was a kit for Rover P6's, or you could use an HIF44 carb set for manual choke.

E Type's were manual choke, so the parts are available.

 

The E Type arrangement that pulls down the jets for enruichment against the diaphragms works very well.

Add to SU's for manual pull down of the jet like the E Type. Part Number AUC - 8654 ~ Then you have a proper manual choke for your slider & red light. (58 in diagram.) Block off AED. Or change float bowl.

 

The choke linkage at the carbs is needed as well, there is a rod arrangement that ran between the carbs and joined the pull down linkage at each carb to a single control cable. You'll need the cam shoe and rod for each carb, as well as the brackets and spring, and the anchor bracket for the cable that attaches under the float bowl.

Did all the small saloons have starting carbs, or were some manual chokes? 2.4's perhaps?

 

FYI, i know that on some vintage british dual SU carbureted engines people have successfully removed one of the carbs from use in the choking process thus eliminating dual linkage complications.

sounds like something worth considering in the event removing the choking process altogether proves to be unsuccessful.

BTW, i'm a big fan of manual chokes and simplification in all manifestations. i own a 2008 honda ST 1300 touring motorcycle. its choke is decidedly NOT manual and doesn't work very well either, and i know why. it's a poor design, entirely dependent on a tiny coolant duct. if it was part of the human circulatory system it would be referred to as a capillary, and like it, as easily clogged and impossible to replace/fix.

i'm beginning to form the opinion (not quite there yet, but...) appears to me that the industry never really developed a reliable automatic enriching system until computer controlled electronic fuel injection systems became standard.

 

Correct JB ~ all I have is the E Type pic I think. Will look.
The 2.4 had a manual slider Bowden cable & red light and Solex carbs until the 240 with SU's & a straight port head..

 

A pic of the anchor bracket for the choke cable.

 

E Type Choke linkage JB is talking about. I have a better picture somewhere. I will continue searching.





Bowden Cable connection.~ From outer cable clamp (far right) to inner cable pinch bolt on the lever.

 

I have some, I'll post them tomorrow.

 

Thanks for all the replies guys ! you've given me a whole new idea about using a manual choke. I wonder if using this on just one carb wouldn't get the engine fired up .
Schmitty

 

That awful solex carby choke did not work very well on the 2.4 engine anyway.
The manual enrichment system on HD6 carbies which drops the jets down does work OK but make sure you have good diaphragms.
Old diaphragms flexing can lead to failure and high possibility of an engine fire particularly from a front carby failure. It will generally pour fuel over the distributor.
The original thermo starting carby system distributed fuel over a wide area in the inlet manifold.
Using only one carby enrichment might work to get an initial start but I think it would require time to warm up before you could get reliable running to drive.

 

if i wanted to simulate a one choked-carb cold start, i think i might disable the standard choking mechanism and richen, temporarily by hand, only one the carb's mixture nuts. then try starting the motor when cold. if i'm thinking clearly (not a given), that should give me a rough idea of whether or not it's at least POSSIBLE to do a cold start with one carb choked.

 

Bill, LAST thing I want is an engine fire ! that's what I'm trying to avoid...Sounds like the maunal choke comes with its own set of possible issues.
Schmitty

 

It's when you try to improve an old design that you start to understand not only how good it was, but also why the engineers of the time made the choices they did.

Often, though not always, the best modif is to restore the device to work how the designer originally intended.

 

Absolutely Bill. Nice new diaphragms are a must do. That said I have zero issues with my Thermo arrangement. You just have to set the needle correctly for ambient conditions in the starter carb (hisser). My car that had 90 thousand miles on it prior to restoration still has it's original red genuine Otter switch on it. The Doctor that owned it from new was a meticulous record keeper.

 

These are some "before" photos I took of a set of E Type carbs I restored. I took them simply for my reference to know how the linkages went, so excuse the sawdust.

These show the centre and end carb, and I've included it here so you can see the rod that joined the choke levers off the carbs, and the centre anchor point for the choke cable. The inner wire of the choke cable attaches through a pin to the centre carb choke lever and the other sheath is anchored to the bracket under the screws of the float bowl.




On the side of the carbs (these are from an Aston Martin, but the Jaguar is very similar) you can see the finger leaver and cam that Glyn posted earlier. In the first photo below, the choke cable attaches to the lever on the right side. As that is pulled to the left, it rotates the cam on the other end of the rod. That contacts the cam shoe ( which has a roller), and that then contacts the throttle shaft via the screw and bracket, plus the lever on the throttle shaft. As the choke is applied, it both lowers the jet and opens the throttle plate to give enrichment and a fast idle, which makes it easier to start. The smaller screw that contacts the throttle shaft lever is how fast idle speed is adjusted. The lower photo is a similar view, the bracket on the right is for the choke cable to attach, that is a slightly different style bracket on the DB5 than on E Type.

 

A qualified maybe. If one one carb is rich for starting ( and assuming the other is correctly adjusted) then you'll only have enrichment on 3 cylinders. In warm weather that might be sufficient, but it will probably be rougher running and more prone to stall as you move until it warms up. As the weather gets colder, the chances of starting decrease quite a bit.

From working on the EFI tunng, I can tell you that the XK needs about 80% more fuel to start at 8°C than it does when it's up to temperature and idling. I'm not sure the choke of a single carb could deliver than much extra fuel.

 

Thanks for all this great info guys ! Love the idea of that linkage for the manual choke ala E type. It is indeed a bit complicated and probably way beyound my skill level - but if I had access to a good mechanic ( I'm new to the local Jaguar Club and long time owners are asking ME if I KNOW of a decent mechanic -- just the info I was hoping to get from them !) and a better endowed budget I'd be inclined to go that route for sure.

I'm remembering my 1972 Triumph Daytona motorcycle. Its choke was missing by the P.O.. However simply by over-enriching the carbs via the plungers enough gas got into the into manifolds to enable a one-kick startup. Then it needed a few minutes of throttle enhancement to get her warmed up and be able to idle and run. That crude type system obviously isn't comparable to the Jaguar's floats /jets, linkage or throttle piston. But maybe I can come up with a creative solution that introduces fuel into the intake manifold with a similiar low-tech / low cost approach. I wouldn't mind having to let the engine warm up for a couple minutes prior to starting my drive.
Schmitty

 

You sound like me and my long string of 7 Alfa's. I always warmed up Alfa's before any performance demand. First by idling then by driving sensibly for a few Km's. Made quite a difference to engine life. I also disconnected the choke mechanism & gave the throttle a few squirts to start ~ massive throttle pumps on Webers. Twin sidedraft Webers with chokes wide open washed all the oil off the cylinder walls (choke per cylinder). Over choking is not a good idea. Alfa's did not like being hammered until all the clearances had normalised. Then with their huge sumps & unstressed oil charge you could drive them flat out all day.