Rich and richer...

... or I could be dumb and dumber? :)

Here is the quick rundown. Motor rebuilt 3 years ago. 94 LT1, M6. 355. All stock components except for higher compression forged SRP pistons, and a 222/222, .471/.471 114LSA cam. I realized after the install, the car definately ran hotter internal temperatures with the pistons than stock. Hot cranking took a little longer (a change to crank advance needed), and I was fouling out my plugs after about 7000 miles of driving.

I tried TR6 plugs and they alleviated the situation but for only a bit longer.

I've recently gone back to TR5s, and made sure the gap was at 0.050. The car idles different and seems to accelerate different as well. However, since I've removed my cat, whenever I downshift to a set of lights, there is a large smoke show when I leave. It is NOT oil, it is a raw fuel smell. Speaking to those without cats, its not a common thing for this to happen.

So why haven't I tuned the car on a wideband since the rebuild and subsequent cam? Good question. However, I'm interested in the advanced look at what the heck is going on here!

I took a look at my plugs with about 1500 miles on them (the TR5s). The electrode has a nice brown wear pattern, but the base of the plug is black. This is how all my plugs come out, black all over. These new ones just aren't black on the tip (yet).

My cam isn't a huge bump over stock. What gives with the excessive black on the plugs and smoke? Is this cam far too much for the stock tune?

I'm vexed over this. I left a set of lights, and could hear and feel the plugs foul until I pulled away. Plus the smoke show, is quite uncomfortable.

Advanced ideas on this? What I can do with my gap? Plug heat range? TO make this better, before a tune?

Thanks in advance!

My cam isn't a huge bump over stock.
Your computer thinks different.

Besides the computer reprograming wich is probably one of the major items and fact of possibly running to cold a plug may play in to effect. But fact is if your running leaded race fuel with the motor the lead will coat the O2 sensor fast and kill it. The car will run super rich if the O2 sensor is coated from the lead. It doesn't take long to get a O2 sensor to read incorrect if your running like I said race fuel alot.

You can try and take a propane torch and clean the O2 sensor. The propane should burn the deposites off the sensor.

I'm not too sure why this post is on Advanced Tech. In essence, you're saying you know you should have it tuned, but somehow you want to solve the problem before you get it tuned. Even a "mail order" tune would probably get you closer than you are, and then you could work on one problem at a time, rather than chasing your tail with multiple problems.

Also confusing.... its running rich and fouling the stock heat range plugs, so you go one step colder with the TR6, and it "alleviated the situation". Doesn't make any sense.... when your plugs are fouling, you look at a hotter plug.

But a modern EFI engine shouldn't foul plugs. Somehow the PCM is getting the mix wrong. One reason would be the slightly elevated MAP from the cam, which the PCM reads as "load". Others might include "false" leans from things like exhaust system leaks, misfires and faulty O2 sensors or wiring problems. Not sure where the issue of leaded fuel came in ... maybe JWINN knows more about your problem than you have posted here.

I'm sure you've already posted this on LT1 Tech.... or you should have. What "fixes" have been suggested and what ones have you tried?

If you haven't tried this on LT1 Tech, I'll move it there, where it belongs.

Thanks for the insight. Let me clarify a few things.

Its my understanding that when the temps in the combustion chamber are too hot for the plugs, then a lower heat range plug is the way to go.

Have I been off on this? If so, I'd be interested in finding out the solution.

Also, I do acknowledge that tuning is necessary, however, what confuses me is why the car runs so dirty, and turns plugs black, with a cam that simply is not much of a bump from stock.

Indeed, the car will be tuned, but this is something that has vexed me for many months.

Does this make it clearer?