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Jaguar 420 Carb problem?

PlaidMan

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Finally got the front brakes sorted and then started the car for first time in 2 weeks and it seemed to be missing on one of the cylinders. I disconnected one plug wire at a time till there was no difference in the engine speed, problem was it seems to be on 3 cylinders. Counting from the front of the car it is 4,5,& 6.Checked compression,OK, loosed the connection between carbs and both seemed to operate ok. Should I maybe be looking at the ignition also even though it seems to have a good spark. I only changed the plugs when we got it running a month ago, filed the points as they looked new. The car also pings heavily upon acceleration so I'll be checking the Timing next but 2 weeks ago it ran beatifully. I'm a little perplexed. Any help appreciated, Charlie
 
Am not super familiar with the 420, but I had a similiar problem with an MG. Turned out the rear carb wasn't getting gas.
 
There have been a lot of problems with the old point style ignition rotors. Try one by advanced distributors, or look for a nos lucas one.( Not in the modern "green box" most of those are made under license, and are not of the old quality). The other thing I see is some of the carb jet diaphragms ( HD6s and HD8s) seem to be reacting with the new gas. some become really haed, and some perish and leak. Check the vacuum feed hose to the brake booster, perhaps it was disturbed.
 
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