Timing advance - when is too much?

[aribert]

Greetings all:

I remember growing up people would say to keep advancing the timing until the engine became hard to crank. My 200 after change in cam & increase in compression is really wanting more timing advance. I was running about 12 deg adv before. Now I have it at 16 or 17 deg advance (centrifical only - no vacuum advance). So when does too much advance become an issue and what is the potential failure mode? My previous post w/ a bit more background - I was searching for a vacuum leak - motor was running quite rouch. Still a very much a loping idle, but the engine really smooths out w/ more advance.

 

[rocklord]

As long as you have no pinging (detonation) during acceleration, you should be good.

Excessive detonation will cause burned pistons, bent rods, holes in block (usually caused by broken rods going thru).

 

[rbohm]

As long as you have no pinging (detonation) during acceleration, you should be good.

Excessive detonation will cause burned pistons, bent rods, holes in block (usually caused by broken rods going thru).

8) this.

 

[MustangSix]

While you certainly want to avoid pinging, the point of best power is not always at the maximum advance that the engine runs without detonation.

It's difficult to determine without a dyno or some sort of road force measurement, but max power usually comes at the point when you can time the ignition to produce peak cylinder pressures just before TDC. That means that you usually have to light the fire earlier (more advance) at higher speeds and later at lower speeds.

You can light the fire too soon and develop peak pressure before the optimal point without pinging. You just lose a little power because the engine is fighting the expanding burn as the piston is rising.