OK, so we put an overhaul kit in the Strombergs of my 74 XJ6. It had sat for a couple of years. The carbs were a mess although it ran OK. The linkage was not opening all the way and the float bowls looked like they were filled with sand. Amazing it ran at all.

Anyhow, after some recent chassis work, I ran it up and down the mountain and found the wide open throttle to be ragged from about 3500 RPM up. By ragged, I mean it did not seem to build further torque and I thought I could feel the occasional miss. I recall the plug wires I changed many years ago and they look fine. I pulled the plugs. #'s 4, 5 & 6 were very carbonized. 1-3 looked fine. (However, the plugs were in prior to the carb O/H.) Replaced the plugs with NGK's.

So, I am trying to figure out what to look at. The distributor was upgraded to a series (3?) electronic one. So, I tend to rule out ignition. I'm still thinking carb.

What would you do next? At least before taking it 75 miles to what is purported to be a Jaguar garage specialist?? Thoughts or suggestions or links or sympathy welcome.

 

I also have a 74 and I have found that the choke cables can sometimes get a little sticky and if stuck slightly on can cause what you're describing. Also, having someone set your fuel to air ratio professionally can do wonders!

 

...I found a loose carb linkage connection, but noticed no change. I gave a friend a carb-balancer and I am going to get it back to properly balance them. I don't expect that to do much though. My carbs have (ugh!) automatic chokes and they are a PITA. It could be one fouling up. Thanks for the suggestion.

 

no problems, I thought about this a little more and recalled that the linkage below the gas pedal itself on these cars can also get a bit sticky... maybe you aren't actually able to get your foot to the floor? Kind of a longshot but mine had issues,so maybe yours could too

 

...but thanks for the suggestion and I will double check it. It is rather that it isn't getting enough fuel. Strange since those carbs are hardly complicated and they were overhauled. Still, something's not right.

 

Hi - Your 74 would've originally had a distributor with a vacuum retard capsule instead of advance. Where did you hook the vac advance on the series 3 45d6 dizzy?

The original carbs don't have the proper ported vacuum fitting for advance so if you hooked it up where that port is (front carb on the bottom) it would activate the advance at idle (where vac retard is active) and if it was timed with that line connected, the timing would be retarded off idle which would really become apparent at higher RPM. Definitely something to look at with the problem you're describing. If the advance is connected to full manifold vacuum that would also be an issue.

 

The distributor is from a Series lll and is a solid state one as I recall. I have not yet taken her home and had a hard look at her but vacuum is definitely on the check list.

 

Do you have the Stromberg "water" choke carbs that use coolant hoses to the choke body? If so I can almost guarantee it is the carbs. These are not rebuildable with much success.
Joe Curto the Carb expert in New York actually jokingly? told me to remove the carbs , find a dumpster and throw them in. Go find a set of manual choke carbs for the car. He felt they are not able to be rebuilt and ever function properly. They are a poor design and fail in the full choke position!

I am an advanced mechanic and in a weak moment thought I could rebuild ANYTHING. These carbs tested my skills to the limit. One additional problem is the carbs were an emission control design and were not intended to be adjusted. There are NO specifications on the carb settings for the jets or any of the other emission ad-ons to the basic carb design. They are an awful design and have several weak design features that make me wonder how they ever worked even when new. My car starts OK but has a rough idle and runs rough until completely warmed up then it tends to run very rich. A total remove and rebuild again did little to improve the situation.

Good luck. Get a set of manual choke carbs and enjoy you car.

 

I agree with William. Dig up a set of SU HD8's with manual choke - waaaay easier to tune. You will have to plug a hole on the intake by each carb. Not sure what it was for but the Stromberg carb intake has them and the SU carb one didn't.

 

down draft Webers work well, provide more power and can be had with manual chokes. Also lots of jets are available and are serviceable by many shops.


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