[TR] The big bang

[tfansher at comcast.net]

You can pull the spark plugs and check the color. Nice grey color indicates a good mixture, black color indicates that the mixture is too rich. It can vary from one carb to the other..... 
Tom 
-Subject: [TR] The big bang 

Hi all, 
Finally enjoying my newly restored 62 TR4. I do have one question - 
usually after driving it for more than 15 minutes, when I shut it off, the 
motor stops & it doesn't run on / diesel, but after maybe two or three 
seconds - Bang! Not a very loud backfire, (almost like a backfire under 
water). 
I just installed a Pertronix kit (what a difference!) but still a backfire. 
I have SU carbs that may be running a bit rich, but I am not sure how to 
quantify. I have been playing with the idle as it has been fairly high 
(1200 rpms at idle) I do have 87mm pistons & a 270 cam with a slightly 
milled head for higher compression. 
Any advice or would help. 
Thanks as always, 
John D