The 'E' Type Forum

Dear Brethren,

Setting up the carbs has defeated me as the jets will not adjust to the correct level flush with the bridge. They are at least 2mm deeper than they should be and the car is running rich.

Run out of options in the manual to resolve the issue so am hoisting the white flag on this one.

Can anybody recommend a Jag specialist in the Lancs area who knows these engines.

Thanks in anticipation,

Nigel.

Hi Nigel....cant help with a mechanic but the jet isnt supposed to be level with the bridge....its set below...2mm is a good starting point......what needles are you useing and are they set flush with the bottom of the pistons..Steve

Hi Steve
Yes the needles are standard UMs fitted correctly in the pistons
I have been following the Haynes manual instructions tr initial car set up which advises to set the jets level with the bridge and then turn them down 21/2 turns
I cannot get the jets anywhere near flush
My problems actually started when I reset the points gap to .015 and then set the static timing at 10btdc
At that point my rich running but nice to drive car started misfiring and running even richer!! Do in my mind need to raise the jets to weaken the mixture
Any advice would be much appreciated
Had to rub hammerite paint off the crank damper to find the timing marks
Goodness knows how it was set up!!

Hi Nigel......is the problem the same on all 3 carbs.....the jets are lifted by a cam lever mechanism this is also attached to the choke mechanism..pulling the choke will drop all 3 jets...sounds like somethings not adjusted correctly....look at the rods connecting the choke to the carbs...there is a section in the manual that explains how to adjust....Steve

Also , get a depth gauge and see if you can set the jets about 65 to 70 thou down from the bridge. This is nearly always a good starting point. The carbs are then set so that each has satisfactory mixture. Then remeasure the depths, average the 3, and set each one to that average . The reason for this is that because of the large balance passages on a 4.2 manifold, and to a lesser extent on 3.8s , each cab setting influences the mixture strength in the other cylinders - this is particularly so with the centre carb

You can buy a set of tools specifically to set up SU's:



Makes setting up a doodle if you have never done it before.

Hi Guys,

Some happy news.

Setting the jets flush as per Haynes is not necessary.

I set them as high as I could without losing the adjusting screws, and then turned them down 2 turns to find via colourtunes that the mixture was far too weak so adjusted the screws accordingly and the plugs are now nice and brown with the engine running crisply with no hunting or pinking.

Thanks for all your good advice,

Nigel.

Heuer wrote: ↑

Wed Jul 22, 2020 11:16 am

You can buy a set of tools specifically to set up SU's:



Makes setting up a doodle if you have never done it before.

David would you mind awfully showing a higher res picture of the instructions in this pic?

Thanks

M

Marcus : I am afraid that I don't think these instructions will help you . The illustration shows a much earlier set of Su s, probably H6 or the like, which have little in common with the HD type carburetters fitted to later Jaguars such as the E type. The tools, I think, are jet centring tools, which are not needed with HDs