Hello Listers
Happy springtime. I have a question about Carbs and Ethanol for my XK120. I have a 1954 SE OTS model and the fuel economy is becoming embarrassing. Recently I noted a worn spot on one of the needles (VR) which I really didn’t expect since the pistons fall evenly with a distinctive cluck. I assume the jet has been affected as well so the tolerances are shot. I have decided to go through the carbs and renew the worn components inclusive of needles, jets and seals. The shafts were replaced about 8,000 miles ago so I feel they are in good shape but I will certainly check.
Before I order new parts I want to know if anyone has an opinion about replacement needles that may allow the car to perform well using 10% ethanol. Currently she runs quite well albeit too rich. Leaning them out helps a bit but I feel there may be something else I can do to inch the mileage up without sacrificing performance. Any thoughts or experiences are, as always appreciated.
Jake Kreeger
1954 XK120 OTS SE 676399
not seeing a reply…I will jump in…a little oblique to your question…as I have no specific suggestion for an “ethanol needle”. I will say: try to find no ethanol fuel. If you must use ethanol fuel a few notes: use an ethanol fuel treatment additive, fill the tank only enough to consume your fuel in about 30 days: ethanol fuel does not age well.(store with a "marine ethanol fuel treatment) Tune carbs/eng normally, slightly rich is better than too lean just so you are not fouling plugs, use correct heat range plugs, and ignore fuel mileage.
Do you have this book?
Hello Nick
Thank you for your imput. Unfortunately here in Maryland finding ethanol free fuel is not easy or local.
My VR carb needles show some wear towards the bottom and I suspect the jets have been somewhat compromised by a subtle rubbing of the needle against the jet so I intend to replace. The throttle shafts were replaced with oversized units some time ago and I believe they still functioning properly but I will check that as well. Timing seems dead on and I run a Pertronix ignition system so it should not vary too much.
I do add ethanol fuel stabilizer as well as octane boost to the tank.
With the introduction of ethanol fuel economy on all of our vehicles “tanked” so to speak. The jag, never that good, dropped about 3-5 miles per gallon. Now it’s down to about 10-12 which I know can be bettered. It is running very rich and adjusting the carbs has not improved the situation too much.I intend to replace gaskets; seal; needles; jets etc along with the vacuum advance unit soon. I will contact Joe Curto prior to ordering and see if he has a suggestion about replacing the VR needle with something that works a bit better. If so I’ll pass this information on to the list.
My engine has never been rebuilt and may just be getting tired. It has 58,000 miles on it and gets driven all year weather permitting with oil changes every 3-5 thousand miles. I also add ZDDP every oil change.
Thank you Mike
I don’t have that SU book though I have one or two others along a original publications from back in the day. I have thought about purchasing on occasion. Perhaps the time has come.
You can wash Ethanol out of fuel , you can see how on youtube !!
After watching a few YouTube tutorials I have come to the conclusion that as much as I dislike ethanol the procedures for removing it are a bit extreme and serve to just increase fuel costs even more. Interesting though and if ever E85 becomes the norm then I’ll re-think the issue.
And now I have added this book to my collection. Found it cheap too. Thank you for the recommendation.
I went thru several alternative needes, only to conclude the stock needles are an excellent compromise. I have a wife and O2 sensor and the numbers sent me on a chase to optimize AF ratio. In particular, optimizing for stoichiometric at idle was not productive. All it produced was a weak idle and no better mileage. I’m going back to stock (new needle and jet).
John