How many times have I looked at trucks/cars for sale and the guy says "it's got a little bigger cam". usually a sales line unless you know the guy. May just have a stock cam. Exhaust always smells like something, right? After all, it's burnt gas. I love it. If it starts, idles and runs good, take britcons advice. Check all vacuum ports/hoses for cracks/leaks too. No gas leaks at carb? No smoke, white or black? Timing off can do this, check timing 6 deg BTDC. Get a good old Rochester Qjet if it persists.
