[Saloon-lovers] Problems with a 420,don't smoke it


Two current problems …

Firstly why does the engine spit back through the carbs ? Sometimes it’s
through the auxiliary starting carb, sometimes through the main carb
Usually just a cloud, sometimes a blue flame. Currently I have no air
filter on; when I replace it, would that affect the problem ?

Secondly, the dashpot dampers keep coming unscrewed by themselves. The
carb does it more than the front. Is this related in any way to the
backfiring ?

Any ideas will be much appreciated, thanks in advance,

Terry Replies,

A good idea would be to make sure your car insurance is paid up,your sure
going to have a fire if you keep running your standard engine without the
air cleaners, (filter).
Replace your Filter and see how the engine runs.

Listers who wish to run without filters,you will need to fit different
richer carby needles,however engines that run without air filters generally
don’t last long.

Foreign particles passing through the carby’s and into the engine wear out
the cylinders,rings,score the bores,pits the valves & or seats.

Don’t think because the air where you live is clean enough for humans to
breath it must be ok for the engine, dirt & debris is drawn into the engine
bay by the engine fan,the forced air flow into the engine bay from the
vehicle moving at speed, small particles of sand, dirt,even small stones &
gravel drawn up from the roadway can kill your engine in just one run around
the block.

Retarded Ign can cause spitting through the SU’s,so will a lean
mixture,leaking air drawn through warn throttle shaft & or bushes,riding
inlet valve,bent inlet valve,air leak into any part of induction
system,cracked vacuum hose,undone,off brake vacuum hose,use a Hose Pipe to
listen for induction leaks,use an oil can to see if the oil is drawn into
the engine,the latter is a bit messy but works.

The starting carby being set alight by retarded ign & or weak mixture,
backfire has been the cause of many Jaguars to be burnt to the ground, other
cars burn just as well with Rochester or Autolite Carbs,it’s not the SU’s in
particular,despite the negative comments scare tactics from some Vendors who
want more $ from you the SU’s really are the most simple Carby that at the
end of the day can give an engine the most power & flexibility & very near
efi economy to almost any engine,even to motorcycles.

If there is a fuel float bowl leakage problem,loose and or broken fuel
lines,banjo bolt seals, if there is even a little fuel vapour under the
bonnet,you could be the first Classic Jaguar driver on Mars, it takes just a
spark from the starter motor to experience up in smoke, Smoking Jaguars are
a health hazard and Governments should see that all Classic Jaguars are
duly labelled

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