Adam Posted August 27, 2007 Report Share Posted August 27, 2007 Hi All, I have an irritating and increasingly common fault on my car – I keep fouling plugs! Once I have cleaned the oil off the plug all is well and I revert to firing on all 6 pots. Engine runs well and in normal operation plugs look chocolate brown. I rebuilt the bottom half of the engine last year but left the head mainly untouched. Fairly sure I losing oil down the valve stems but before I rebuild the head has any body got any other suggestions? Car is running carbs with standard ignition. Thanks Adam. Quote Link to post Share on other sites
Tom Fremont Posted August 27, 2007 Report Share Posted August 27, 2007 Adam, You might want to check the plug type, as many references show a cool plug for carb 6s where a hotter one is warranted. TR250s needed a hot plug and late TR6s and I think all P.I. types called for the cooler one. For reference: HOT - Champion N12Y NGK BP6ES COOL - Champion N9Y NGK BP7ES If you're using the cool ones now, you could see if going hotter solves your problem ( did for me back in 1977 - haven't looked back! ) Quote Link to post Share on other sites
jonlar Posted August 27, 2007 Report Share Posted August 27, 2007 Hi Adam, is the fouling on all plugs or any one in particular - have you got the auxiliary rocker oil feed line? Quote Link to post Share on other sites
Adam Posted August 27, 2007 Author Report Share Posted August 27, 2007 I am running the hot ones NGK BP6ES. Would you recomend going hotter ? No oil feed fitted. Most of the time pot 1 and 6 are the culprits. Keep- the sugestions coming - ta Adam. Quote Link to post Share on other sites
Adam Posted August 27, 2007 Author Report Share Posted August 27, 2007 Quote Link to post Share on other sites
JohnC Posted August 27, 2007 Report Share Posted August 27, 2007 The symptoms you describe sound the same as the ones I had before my engine rebuild. I did change the valve guides, and the problem went away - no proof however that this was cause & effect. One classic tell-tale of worn valve guides is the puff of smoke after each gear change. Have somebody drive along behind you and watch. I understand this is caused by the increased manifold vacuum (when you lift off for the gear change) sucking oil down the valve guides. I managed to delay the inevitable a little while by switching to hotter plugs - BP5ES cope just fine. In fact I still run these in pots 5 & 6 to combat the slightly richer mixture (not an issue for you). You could also try fitting valve stem oil seals. I've never done this, but you'll find several references to this in past posts here. Hope this helps, John Quote Link to post Share on other sites
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