Can't get my Xk120 1953 to run smooth. I've got carbs rebuilt, new pertronix ignition, as well as new sparkplugs, new sparkplug wires, & coil, installed. Compression is 138, 144, 147, 140, 150, 155. Starting carburator kicks off runs alittle smoother. Car sat for 10 years I've been working slowly with it for last one year. Thought I might remove valve covers, start engine and squirt Marvel Mystery Oil on valve stems and see if engine will run on all 6 cylinders. Has anyone had a similar problem? Car was only run for less than 1000 miles in the last 20 years. Any thoughts or advice is sincerely appreciated.

 

I presume you drained the old fuel out of the tank, put in new fresh fuel, and replaced any fuel filters that were in the lines?

 

Yes I did, new fuel, new fuel filter, flushed out gas tank, new fuel pump. I've slowly gone through the steps. Thanks. george

 

How many miles on the car ? The cylinder compressions seem to vary a lot, but may balance up a bit if you run the car a few miles. Standing a long time can make the valves a bit lazy coming back off the cam despite the valve springs being pretty strong. Essentially it needs a bit of use and then you can assess what more work might be needed. Has the head ever been off the engine ?

 

Thank you for responding. Yes the head was removed and new valves were installed (years ago). My brother a retired mechanic hand lapped them in with Corpus Blue I recall it took him forever to do it. The car has never really been driven very much since I've had it. I purchased the XK120 at auction in 1982 I believe and drove it for fun, although it was less than a grand total of 900 to 1000 miles. Total mileage on the jag is 67K.
I'm retired now and decided to enjoy it. Yesterday I removed the valve covers and started the engine, I squirted Marvel Mystery Oil on the valves while it ran (briefly) to much oil coming out. Per advice I received to loosen up a possibly fouled valve spring. Today I've got to clean up the mess and see about driving it.

 

Check needle adjustments for equal enrichment. Check that both butterflies are in sync. Then check both dampers for smoothness and make sure oil is not overfilled in reservoirs. Then reset dwell and timing.