The C61CX is at the top of the heat range! They make a C63CX and it is at the top. They also make cooler C59CX, C57CX, C55CX and C53CX. I have attached a chart showing these numbers hot to cold. So my C61CX is one of the hottest heat cycle plugs. So now my question is how far to go down in heat range?
Thanks! MJ

are these aluminum specks on the plug??

I like NGK’s.

At 12:1 you’re in the -7 or -8 heat range(higher is colder).

I run NGK #8's at 12.1.1 comp and they last a long time on the street testing carbs and general cruising BUT my motor is in a pretty optimum tune verified by track times, afr's, plug readings and a good street tune before I hit the track. Plug looks glazed over which is as stated HOT combustion chambers weather too much timing, lean, too hot of plug etc...........Good luck...........

Rule number one is NEVER use a cross reference for plug heat ranges. They are somewhat close approximations, but not good enough to use as a fool proof heat range indicator.

Again, like I said, I don't think you need the cut back ground wire plug. At your compression ratio, you just don't need it.

IMO, you'll be better off with an extended tip plug.

The C65YC and the C65C are both two ranges hotter than what you are running.

I'd have to look but I'd bet the plug that Porter just posted isn't a cutback ground wire plug.

So as I said, I'd order the hotter plugs and start over after you verify TDC and your timing light.

Don't be married to the CX plug. It may look cool but you just don't need it.

BTW, did you mention what ignition you have? That sort of greenish tint can be from a weak ignition.

If you call NGK they will recommend the correct heat range. At 15-1 I run -9. I would bet at 12-1 the suggestion of -7/-8 is very close
Doug

The ignition is MSD all the way!
MSD distributor, MSD coil and MSD coil wires. New cap and rotor also.
MJ

Which MSD box?


Like AndyF said many posts ago...your plugs look strange. At first look I thought they were too hot and reducing timing and adding fuel were keeping it from killing itself.


Once we got deeper into it, it seems to me those plugs are plenty cold for what you are doing. That doesn't explain the green tint, what looks like a ton of heat and not being able to see a timing line on the ground wire.


The insulator should be a dull white from the top down to the fuel ring. Most likely, you'll see some clouding on the porcelain from coming up the return road, especially if you don't run a power valve.


The plugs look strange and your timing is also an anomaly.

Is the ICU a 6,6A,6AL, 7AL2 or which MSD box are you firing the coil with and which coil are you using?

As stated in so many ways, your timing is not at 28 degrees. Get the timing right and put some of those recommended above new plugs in, and go again.

From all the replies and ideas I am going to verify the timing first.
Then before I make my first pass I will install one of the recommended plugs and see how it goes. If it looks rich at that point I'll adjust the carb.
Thanks! MJ
P.S. The MSD box is a 6AL with a MSD BLASTER 3 coil.