I have just finished restoring my 1955 XK140 FHC and am in the process of breaking in the engine and have put about 500 miles on it and the restored chassis. It is a C-type engine. I had the SU H-6 carbs rebuilt by a reputable and trusted firm and noticed the carb needles are stamped “TS.” Using the “SU Carb. Company Catalog”, page 75, I find the TS needle compares closely with the “rich” SA needle. The engine is indeed running a bit rich and I‘m sure this was intentional as the engine is in the process of being broken in after a complete teardown and overhaul. I am at sea level.
Here are my questions:
After putting the specified 1,000 break-in miles on the engine, should I continue to run with the “rich” TS needles in the carbs or should I switch to another, more standard needle such as the specified “SJ” needle.
What are others experiences running different carb needles, and what do you use? Again, I’m at sea level.
Keep checking the color of your spark plugs after a run, if they are black you will have to weaken the carbs, if this does not help after weakening and plugs are still black you will have to change to a weaker needle.
WO2 was the needle spec on my '56 type “C” engine(H-6 carbs). IIRC, this recommendation was arrived at after production started in response to reported drivability problems…“spitting back” or other lean mix indicators. BUT, modern fuels may have rendered original needle specs obsolete so trial and error is probably in your future.
Thanks gents. I appreciate you taking the time to respond to my questions. I’m sure you are correct myfdun and this process will be iterative. Thanks Lee for telling me you have the WO2 needle. The WO2 needle is even richer than my TS needle in the mid-load range, so possibly I’m not too far off. I plan on putting another 500 miles on my TS needles, then begin the iterative process with different needles, while staying on the rich side rather than lean. Fortunately, these 0.100" fixed needles are easy to replace.
Next question: Is there someone stateside who has a wide assortment of needles I can purchase and test?. I’m happy to go to Burlen, but it may be easier to purchase over “here.”
Mike are you aware of the needle comparison web page called ‘Minty lamb’
as long as you know the jet size in your SU’s you can compare up to four needles at a time.
A couple of months ago I was on the phone to Burlen asking about needles for a non standard tune engine. The Burlen tech referred me to the minty lamb website.
There is also winSU, which will run on windows 10.