What are the smog bumps that I keep reading about? Where are they located? I guess if I had a set of heads off I could see them.
Where can I find an artical dealing with polishing and porting heads?

 

It's that big lump downstream from the exhaust valve guide that's drilled for the thermactor ( air pump ) system. It's a huge restriction and you can barely fit a finger between it and the floor of the exhaust port. You can see it easily with the exhaust manifold off.

 

Here's site that provides detailed porting information:

http://sa-motorsports.com/diyguide.shtm

 

I may have lucked out here. I just 'freshend up' my 77/460 and when I did the head's, I didn't notice any bump looking restrictions in my exhaust ports.
I'm pretty sure my engine is the original, but when I pulled it down, it had two different head gaskets.

On polishing the ports...
That's a common misconception of increased breathing.
You may wonder why the ports of the stock engines arent Polished, or at the least, very smooth.
I'll try to repeat what an engineer told me back in the 50's.
Any medium (Air/fuel mixture for example) travelling through a Pipe (Manifold) will develop a layer of static air (unmoving, hard air mass) clinging to the surface of the Pipe.
The higher the speed of the medium, the thicker the static layer.
This in effect, reduces the inside Diameter of the Pipe.

All those little bumps and rumples are cast right into the manifolds.
They cause turbulance which further causes the mixture to be broken up into very well mixed little ***** of Fuel/air, which become a very equally dense compustable gas in the compression chamber.

As for the exhaust,you need some scavenging of heated gasses to aid in the input air-flow, and to help heat up the fresh cool charge of Air/fuel mixture coming in behind it.
I'm certain you'd get a lot better exhaust flow by removing those bumps. Who knows why the engineers had them installed. But you might not even notice the change. However when it comes to the emissions tests (just over the horizon) it might make a difference in whether you pass or not!

With the exahust and Air/fuel mixture moving too fast, you get reduced highspeed performance. Almost untrouble-shootable missing at high speeds. This is if your Cam, ignition, etc etc is not configured for running at that speed.

So this is something you should only do to a Track racing machine that runs best at a narrow Tach angle. You can get Super High horspower at that narrow Tach angle (RPM spread) because the Intake and exhaust are tuned to work at that Air/fuel mixture speed (flow).
But on a daily driver, it has the effect of reducing the take-off power and limiting the peak performance to a vary narrow band. Worse yet, a hacker like me could never predict at what RPM that band of power might occur when I alter the Mixture/exhaust flow.

If your still not convinced. Put a tach on your lawn mower. Get a reading for a starting place. Then, port and polish the poor little engine and run the same tests.
You'll actually see a drop in power when you hit the tall grass, and a little difficulty in starting it. It'l be a little slower to get up to it's operating RPM as well.

All this'll cause a lot of arguments, so I'll say in advance, that all these theories are not mine. They come from Engineers, who have a lab with Dyno's, and tech's to make changes for them.

So c'mon back with your questions and let's rap them down.