I bought a set of colortune plugs to set up my carbs - they are fantastic - I can highly recommend them for optimum tuning! They have however highlighted that my no.6 (front) cylinder runs hot. The plug fouls up very quickly and misfires after a few hours running. I cant seem to get that cylinder to run with a blue flame (seen thru the colortune plug) - it's always orange no matter how weak I make the mixture on the front carb. Could this be an spindle shaft air leak or float chamber problem, or am I looking at a piston ring/valve problem? I tried the old teaspoon of oil down the cylinder trick; which pointed towards the piston ring - but I cant help but think it might actually be my carb that's causing the problem, as the rest of the engine runs sweet. (he says in hope that he doesnt have to take off the head!) Is this something I should worry about? Should I do a carb rebuild first. The car only has 23000 miles on it.

Thanks for any advice you can offer, Scott
1967 XKE Series 1 4.2 Roadster

Submitted by ianc@uvic.ca on Wed, 03/01/2006 - 21:50

My instinct was always to say "ignition" when a customer came in with a one-hole problem, so be sure you've really eliminated that. But you might check the valve clearances. A choked exhaust can do that - carbon anywhere from the valve to the header junction.
1969 E Type

Submitted by dmartin@coinstar.com on Tue, 01/17/2006 - 12:12

I'm a believer in the Colortune plug too for home use. I recently bought another one (used) so I could replace two plugs at a time and compare them in real time side by side. I have 3XSU's.

I have a similar problem on cylinder 6, at speed it's blue and at idle it's black and weak, like a misfire. It also produces high Hydocarbons on my mechanics analzer at idle. The kicker is that #5 is fine at speed and at idle (blue), so it points to something other than the front carb.

I've replaced the plugs, the #6 wire and have a Pertonix unit in there, but still it has problems on #6 at idle. Also the left tail pipe puffs, and the right doesn't no matter what I do, I'm begining to think it's something inherent to the internal design of the intake manifold. BTW, both my engine and head are new.

Try using the Colortune on #5 and see if it looks dialed in.

68 E-Type OTS, 90 VDP Majestic