[ROVERNET - UK] De-coking a rover V8

Gundry, Kenneth KG at dolby.com
Mon Feb 6 23:39:24 GMT 2006

You might be amused at the following from the service manual of my

The engine can be decarbonized without removing head by making use of
the oxygen process. A cylinder of compressed oxygen is necessary, also a
strong flexible tube with a metallic nozzle of suitable length and shape
to allow it to be inserted through the sparking plug holes, and to be
turned round inside the head so that the stream of oxygen can be
directed on to every part of the combustion chamber and piston top. A
piece of in. external diameter copper pipe, curved about 3 inches from
its end, is suitable.
First turn off the tap on Autovac controlling supply of petrol to
carburetter, and run engine until carburetter is quite dry. Remove
bonnet completely by lifting away from radiator and from clip on dash.
Protect wings and dash with suitable coverings, as the carbon leaves the
cylinders in the form of burning granules. 
Next rotate the engine until the exhaust valve of No. 4 cylinder
(farthest from radiator) is just closing. (The position of exhaust valve
can be seen through sparking plug hole.) The piston of No. 1 cylinder
will now be approaching top dead centre, and, when exactly at top of
stroke, No. 1 cylinder will he ready for decarbonizing.
Now turn on oxygen until a fairly powerful stream emerges from nozzle of
pipe, and direct this stream at sparking plug hole for 30 secs. Then
touch edge of sparking plug hole with a lighted taper, and the carbon
will immediately catch fire. Gradually work the nozzle all round the
interior of the combustion chamber, and on to piston head taking great
care not to allow it to remain in any one position for more than a
moment, until no more carbon emerges. During this process, the operator
should stand well out of the path of the burning carbon. 
When no more carbon emerges, the oxygen should be turned off, and a
stream of compressed air should be directed into the combustion chamber
just cleaned to remove any fragments. (A few strokes from a powerful
tyre pump will accomplish this if no compressed air is available). 
To prepare No.2 cylinder for decarbonizing, turn engine until exhaust
valve of No.3 cylinder is just closing, and set piston of No.2 cylinder
on top dead centre, proceeding as before.  To prepare No.3 cylinder, set
piston on t.d.c. with exhaust valve of No.2 cylinder just closing.  To
prepare No.4 cylinder, set piston on t.d.c. with exhaust valve of No. 1
cylinder just closing. 
The entire operation can be carried out inside of 30 mins., and a 10 ft.
cylinder of oxygen should be sufficient for one engine.

Ken G, 1925 Rover 16/50 (San Francisco) 

-----Original Message-----
From: rovernet-bounces at lyris.ccdata.com
[mailto:rovernet-bounces at lyris.ccdata.com] On Behalf Of
Gavin.Walker at csiro.au
Sent: Sunday, February 05, 2006 10:05 PM
To: rovernet at lyris.ccdata.com
Subject: [ROVERNET - UK] De-coking a rover V8

  Last year a stuck inlet valve bent a pushrod 45deg.  I have finally
taken the heads off.  All the valves appear straight.  One valve guide
on the other head has dropped and cracked but the valve seems ok.  Some
of the exhaust valves are a little stiff in the last few mm of movement
but I expect that'll disappear when I clean them up.

The carbon is really thick on both the heads and the pistons.  What the
best way of cleaning this up?  

The head gaskets show signs of cylinder leakage between the cylinders
and into the valley.  Heads and block, however, are flat within 0.05mm.
Don't know what's going on there.

Gavin Walker
Canberra, Australia

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