Snyder 5.5 Changes Things

[Dick M]

I have the 5.5 head on my coupe. One way to find optimum advance setting is to continue retard the spark until the knock goes away. I find with mine that the knock is gone and optimum power is achieved with the spark advance about 1/3 down. I believe Les Andrews advises against too much advance with the higher compression heads.

 

[Mike V. Florida]

I have the 5.5 head on my coupe. One way to find optimum advance setting is to continue retard the spark until the knock goes away. I find with mine that the knock is gone and optimum power is achieved with the spark advance about 1/3 down. I believe Les Andrews advises against too much advance with the higher compression heads.

"With increased flame speed, if the timing is not sufficiently retarded, too much of the burning process will occur early when the piston is in its top dead center position. At that position, the piston is static for an instant and resisting downward motion. While the piston is temporarily static, the heat of the flame is increasing the chamber temperature which will promote detonation. Any great rise in heat also necessitates the need to further retard the timing because the heat increase makes the mixture burn even faster."