Edwin Posted June 17, 2015 Report Share Posted June 17, 2015 Hello, I'm not really having any issues with my TR6 other than the fact that the spark plug in cylinder 6 is rather black (dry). And this has been so for a couple of years. The engine has been fully rebuild and is fitted with 2 SU HS6 carbs (bought them new a couple of years ago) and 123-electronic ignition dizzy. Other than that it's a standard engine (US spec) Spark plug 1 through 4 are perfect (light brown). Number 5 is a bit darker an number 6 is quite black but dry. Plugs are NGK BP6ES. What could be the cause of this ? The car starts and runs very nice, doesn't burn oil and does about 24 MPG. Cheers, Edwin Quote Link to post Share on other sites
alec1978 Posted June 17, 2015 Report Share Posted June 17, 2015 Hi Edwin, Over fueling usually turns the plugs black. What's air filter and set up is on the car? Regards, Alec Quote Link to post Share on other sites
Graze Posted June 17, 2015 Report Share Posted June 17, 2015 (edited) Edwin Check the throttle bodies are synchronized and letting same volume of air into 5 and 6 If the spindles or linkages are worn and the butterfly plates arent opening with the others the lack of air causes the over fueling mentioned by Alec There was a thread on here recently with an air flow meter recommended - I'll see if I can find it and add to this. Here it is. See post no 2 has a link to te meter. I bought one. Works a treat! http://www.tr-register.co.uk/forums/index.php?/topic/52163-inlet-manifold-balancing/ Graze Edited June 17, 2015 by Graze Quote Link to post Share on other sites
peejay4A Posted June 17, 2015 Report Share Posted June 17, 2015 ...it's on carbs but still worth checking they're in sync. Quote Link to post Share on other sites
Edwin Posted June 17, 2015 Author Report Share Posted June 17, 2015 Indeed... it's on carbs and have checked the air flow on both carbs. They are perfectly synchronized both at idle and at about 2000 rpm. And it must be that the mixture in 6 is too rich. But i'm a bit puzzled as to how only number 6 is getting less air or too much fuel. If the setup of the rear carb would be different from the front carb shouldn't plugs 4, 5 and 6 show the same issue ? Quote Link to post Share on other sites
stuart Posted June 17, 2015 Report Share Posted June 17, 2015 Plug lead or plug or compression problem. Stuart. Quote Link to post Share on other sites
Peter Cobbold Posted June 17, 2015 Report Share Posted June 17, 2015 Plug lead or plug or compression problem. Stuart. +1 and check the disy cap isnt 'tracking' HT to earth on #6. http://s789.photobucket.com/user/Jaysgarage77/media/Badgersport/madness3007.jpg.html note fine lines of carbon on old cap on right of page. Quote Link to post Share on other sites
john.r.davies Posted June 17, 2015 Report Share Posted June 17, 2015 Some say - and I'm not talking Stig - that the plenum starves No.6 of air, the previous five robbing all that can get in. Try a run without the plenum, and another plugcheck. John Quote Link to post Share on other sites
stuart Posted June 17, 2015 Report Share Posted June 17, 2015 Some say - and I'm not talking Stig - that the plenum starves No.6 of air, the previous five robbing all that can get in. Try a run without the plenum, and another plugcheck. John Keep up John its a carb car. Stuart. Quote Link to post Share on other sites
Edwin Posted June 17, 2015 Author Report Share Posted June 17, 2015 Just checked compression and readings are exactly the same on all cylinders and I know it isn't a faulty plug because I changed the plugs a while back ago and no difference. But I also tested the plug leads with a multi meter and voila... plug lead on nr 6 is faulty. The connection of the wire at the plug end is loose so it sometimes makes contact and sometimes doesn't.... So I'll be ordering a new set of leads. Thanks !!!! Cheers, Edwin Quote Link to post Share on other sites
john.r.davies Posted June 18, 2015 Report Share Posted June 18, 2015 Good point, well made, Stuart. I'll get m'coat. John Quote Link to post Share on other sites
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