I did a little experiment in the weekend.
First, background on why Im not confident in my timing torch. Its a cheap one from Helfords (cant remember the price, but under 100), and it has a dial on the back so you can adjust the strobe. In theory this makes life easier as I just put a dab of whiteout on the TDC mark on the front pulley, then I adjust the dial on the torch so that the timing mark on the cam cover is pointing at this TDC mark. I can then read off the dial what the timing is. Well, the feel of this dial just doesnt fill me with confidence. You can wind it way past zero backwards, and there are no notches or anything to give me the feeling its a digital dial rather than an analoge one.
So this weekend I did two things.
Built a 'step' curve (ie, right angle jumps, not curved) for the 123. so 0d at 0 to 1000rpm, then 10 to 1500, then 20 to 2000, 25 to 2500rpm. No vacuume for anything
I then used my torch and reved the car and adjusted the dial to make sure it jumped in the steps I expected. This actually worked really well, and I got the 10, 10, 5 degree jumps I expected.
Next was to make sure the zero was correct. This is set by having the engine at TDC on number 1 and disconnecting the neg from the coil. You just turn the 123 clockwise until a little LED just comes on. Pretty easy.
Since my normal curve has 10degrees at idle, that means the total idle advance should be 10 degrees. Both my torch and a borrowed one (VERY old and dodgy looking) agreed within 2 degrees. I then loaded a curve with 5degees at idle, and tested again. Same thing.
so, timing is where I expect it to be, and I can probably trust my torch now.
I have put new plugs in, and replaced all the HT leads (with fancy spiral core 8mm ones). I'll check them again next time I get a chance and see if its fixed itself.
What does the colouration of my spark plugs mean though? Its like its running a little rich at the base of the plug, and a bit lean at the top. Is this to do with the heat range of the plugs? I'm using NGK BP6HS plugs with gap at .028
I've been reading this:
http://www.4secondsflat.com/Spark_plug_reading.html
and it seems to suggest I'm not far off, I've jsut never seen the distinct colour change up the earth leg before.