47A ignition timing-

Don't ignore the rest of it -- that is, take it out and see if it pings. The ping is preignition and it causes nasty pits in piston tops and valves. Never seen one actually melt, the pits are bad enough, but can be avoided by backing down the timing.

The whole idea is that an older engine doesn't seal as well as a new one. Therefore the mixture in the chamber doesn't burn as rapidly and takes longer to achieve the same force it would if it were under higher pressure - so you can trigger the spark a little sooner. If your engine is making more speed with more advance - while mixture and everything else stays the same -- that should tell you it's more efficient at more advance -- it's using the explosions in a better way and turning faster because of it. Just remember that you're only turning a flywheel when you're sitting there, and the story changes when you're under load. The other thing to watch for is that you're not running too hot with more advance, which you can tell from reading the plugs.

I'm guessing you're not trying to extract maximum performance from your A, and are probably more interested in preserving it. So be careful. The other post was about a guy who had rebuilt an engine with higher compression ratios and therefore more compression than stock -- and was needing to back off timing because of it.

As a P.S. -- my popper only has a couple of timing marks. Is 58 something you're reading, or guesstimating?

Steve

Wow..! If you're going to use nice big bucks stuff like a digital timing light, you might also want to consider an EGT (exhaust gas temperature) gauge. That helps you see the result of timing and mixture changes almost as soon as you've made them. Another idea would be a knock sensor to tell you when you've gone too far. I've heard that a Japanese operation makes them for aftermarket.

Steve

The manufactures spend lots of time and money trying to determine the maximum timing an engine can tolerate without damage to the pistons or other internal engine parts.

Whenever possible use the manufacturers specifications to set the timing they usually aren't very far off.

I don't know about piston damage if you are still running cast iron pistons but valve damage is a real possibility if you run excessive ignition timing.