Hey! what is that smoke coming out the back of my SVX anyway?????

[svx_commuter]

Hey! what is that smoke coming out the back of my SVX anyway?????

I am looking for opinions on what makes smoke come out the tail pipes. So go on and jump in here if you got any idea at all.

I’ll run through a few of the facts:
Engine 250k miles and climbing
Leaking rear engine crank seal
Transmission with about 260k miles since it was rebuilt before I bought the SVX
Trans is leaking out the front some but not real heavy.
The engine uses a quart of oil oh about every 1000 miles
The trans uses about 1 qt every 15,000 miles or so. 2 qt per year
The PVC system looks clean with no oil in the hoses

So here’s the smoke part. I have been trying to get better gas mileage because I drive a lot. Hey I have been doing better in this area I have been getting around 28 mpg which is a lot better than the 24 I used to get.

It has been my thinking that by being light on the accelerator and never nailing it I would get great gas mileage. Well then when I do nail it maybe after about 2 months of light throttle driving there is a cloud behind the SVX. So then if I do it again there is less of a cloud and the third time no cloud at all……… Then if I drive for a day which is around 120 miles and nail it again there is no cloud.

Now one time a guy I know was behind me. I was showing off and nailed it. The cloud appeared behind me. He said the engine was running rich when he saw the black cloud and said it was running rich because it was black and not blue. Yeah I just nailed it and pulled away from him and left him in the gas cloud.

So what do you think this is?

How can it run rich and then not run rich after repeated throttle stomps?
Can it be carbon or something else from the catalytic converter that gets blown out?
Can it be carbon from build up on the intake valves that gets blown out?

Thanks and take care of that SVX

John