Jordon T Posted February 7, 2014 Share Posted February 7, 2014 Hi Guys,My Herald 1200 is running a single Stromberg CD 125 which I have been using for quite a while now with great effect. But having done an engine change recently I have noticed that my spark plugs are different colours and that the car is using a lot more fuel. The spark plugs on cylinders 1 & 2 are black and sooty (rich) and the spark plugs on cylinders 3 & 4 are a beige/tan colour. The exhaust pipe tip is very black and sooty.I have tried leaning the mixture more, but the engine starts to shake and miss.The engine has a 12-52-52-12 camshaft (Not ideal, I know), with a 9:1CR cylinder head and a 12/50 inlet/exhaust manifold. Everything else is pretty much standard.Other than this the car drives really well.Thanks Jordan :) Quote Link to comment Share on other sites More sharing options...
Jordon T Posted February 7, 2014 Author Share Posted February 7, 2014 Here are some images of the Plugs. Quote Link to comment Share on other sites More sharing options...
ferny Posted February 7, 2014 Share Posted February 7, 2014 Check the valve clearances. I guess you could also have an inlet leak near three and four so as you're settling the mixture to compensate and make one and two correct the others are going far too lean. Quote Link to comment Share on other sites More sharing options...
Mark Hammond Posted February 7, 2014 Share Posted February 7, 2014 IMHO That cam is very ill matched with the head and the carb is wrong, you need a hotter cam, Spit inlet manifolds and one and a quarter inch SUs to make it all work nicely and to get the best from that head. Unless you wanna sell me those SUs that is…. ;)Mark Quote Link to comment Share on other sites More sharing options...
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