XK 140 engine with C head, carb needles?

Hello Folks,
I rebuilt a 3.4 liter XK engine that had been salvaged after the body was abandoned after an accident years ago. I installed 9:1 pistons when I rebuilt it 4 years ago. I have it installed in a 120 coupe and getting it ready for the spring. I am wondering what carb needles folks would recommend considering the ethanol laced fuel and the increased compression from the original. It has the original cams.

Many thanks

Wes Keyes
York, Maine

This picture is from the official SU carb chart.

You can order needles from Burlen or Southern Carburettors.
Both here in U.K. details on their websites.

What I forgot to say, is that at the bottom of the page that I cut off the photo, it says for the H8 carb, add a U to the letters. So, UVE and UVR. I have a set of UVR’s that I tried in my car that has HD8’s.
They are too rich for the HD8, but maybe ok for the H8 carb ?

Thanks John,
That is very helpful.


The 120 FHC and DHC had the air cleaner out in front of the radiator, so it took different needles.

RC looks like a pretty close match to your combo…120, 9:1, “C” head. My 8:1 140 “C” came with WO2 needles, but the modern fuels will mess with the original recommendations…I would think somewhat richer needles would be in order.

Hi Wes,
I have 9:1 pistons, a B head, dual exhaust, custom profiled valve seats, and cleaned up ports. The carbs are fed by a standard front mounted air filter. I started with the standard W02 needles as originally supplied with the FHC but found them to be way rich. I checked them with a dual channel air fuel monitor and could not lean them out properly. I then swapped to SJ needles (three steps down in the XK needle chart) and the engine runs beautifully. This is an ongoing project but I feel I am close now and I’m not gassing out the car behind me.

Hello Wes,

Most of the answers on here are supposing you have H6 carbs. But, some C type heads have H8’s which are 2” not 1 3/4 like the H6 on a normal 120 or 140. The H6 has a 0.10 jet and the needles are thinner on the shaft and shorter. The H8 has a 0.125 jet and longer needles.
I have H6’s on my Healey 100 and HD8’s on my 120 FHC, but do not have the normal trunking and filter at the front of the car, just straight out throats with gauze filters. On my HD8’s I am using UN’s having tried UO’s. E type standard is UM, but all the tuners I know say it is far too lean.
You have not said which carbs you have ?

Just realised the chart I put on here before had the important top of the page cut off where it describes WEAK,STANDARD,RICH
Also I have attached copy of 0.100 needle chart.