When to de-coke?

[David53]

Any tips on when a de-coke is required? I noticed recently that on startup from cold I am getting some black specks on the garage floor from the exhaust pipe. Engine has covered prob around 7,000 miles from rebuild which is a bit early but do modern petrols result in more carbon? What are the other signs a de-coke is required, and any tips for carrying it out?

[bmcecosse]

Never! Modern fuels= much less chance of 'carbon' build up. Just check/reset the valve gaps and all will be well.

[chickenjohn]

Only need to de-coke if you have pinking and running on and all other possible causes have been eliminated.

I had to do this on my Traveller when I first got the car. A simple de-coke and grind of the valves did a world of good to the engine. Only necessary if the car has been driven slowly a lot. As I often take the car up to 50-60mph for an hour or two a repeat de-coke has not been necessary in my ownership.

[JOWETTJAVELIN]

I am getting some black specks on the garage floor

If you could see the amount of soot left behind by mine, you'd have a fit. Seriously, there's a board behind by car and this turned black after just one start-up.

Just keep smokin' along and you'll be fine. Take it on a long, high-speed run, and that will dislodge any clag from the head.

Soot does come out when cold-starting due to the use of the choke, and condensation in the exhaust taking soot with it.

[Dean]

I get black specs on the floor too, as there are no huge flames coming out of the exhaust, I can only assume it is due to running on choke.

[beero]

Black specks from mine too, seems normal then?

[bmcecosse]

As long as the plugs are light beige/almost white after a good hard run - there won't BE any carbon......

[David53]

Thanks for the advice. It does seem the black specks are when starting on choke.

[mike.perry]

I have a black patch on my white garage door.
In Jowett's case it is probably bits of big end bearings

[JOWETTJAVELIN]

Soot:


[frame][/frame]

[dalebrignall]

mine does that all normal dont worry about it

[moggiethouable]

Mine had it too, but I took BMC'S advice and reset the tappets and the net result was much better.

[David53]

Just curious - why did petrol of the 1950's produce carbon but today's does not? Is it because modern petrol is unleaded?

[bmcecosse]

No -but it was cheap, so folks didn't mind running rich - and using plenty of choke on start-up!

[MarkyB]

I think modern formulations of both oil and petrol contain more cleaning agents, I'd be surprised if refining techniques haven't changed a lot since the '50s.