340 compression ratio

Steve,

If the engine was built for racing, I don't think you can assume anything is stock. With that cam and intake, I'd guess that there was more work done inside. Which probably means the bore isn't stock. Pistons may not be stock. As far as the chamber volume, those heads are usually in the 65-72 cc range. That's per chamber. Most compression calculators do the math for you on the conversion to cubic inches. But, you won't be able to find out the EXACT chamber volume of your heads without removing them. From the factory they varied, which is why a range of 65-72cc's is given. Some are as small as 65cc's, some are as large as 72. And if the engine has been rebuilt, the heads may have been milled, which changes everything.

What are you trying to figure out?

I'd do a compression check to start off with. Dynamic compression doesn't translate directly over to static compression, but it'll give you an idea. Heck you can even just pull a few plugs and look at the tops of the pistons, should tell you if they're domed, dished, flat, etc. That should help get you in the ballpark. Ie, if they're flat top pistons with those heads, the compression is probably less than 10:1. If they're domed, it could be anywhere from 11:1 or up.

As far as the carb goes, black soot isn't from running too low of an octane. Its from running rich, which is an entirely different problem. And if its in the carb, its from backfiring, otherwise they're won't be any soot on the carb. Dirt maybe, but not soot from combustion.

Got any pictures? :D