Originally Posted by
JieM
Thanks Telemaster for your answer.
But do you have measured it on this engine ?
Here the result of my measurement. How do you explain this ?
JM
How are you measuring the degrees BTDC? Of you are using a piston stop, that explains the variance. You're not measuring crankshaft degrees but rather the distance of the piston from TDC
I reiterate; Unless the bores for the slave rod link pins are mislocated in the master rod, crankshaft degrees will not vary.
Will this affect detonation? Yes it will but it has nothing to do with crankshaft degrees.
Put a protractor over the master rod and measure the degrees of the link pin bore C/Ls. If they are all at 120 degrees then the timing of crankshaft degrees will not vary between cylinders.
It's geometry. If you are varying the timing to reflect 30 crankshaft degrees BTDC then your ignition is occurring at different distances on piston travel BTDC. Perhaps the variance is designed in to reflect piston travel instead of crankshaft degrees? I have an FA-450 master rod in my parts bin. I will measure the C/Ls of the link pin bores.
BTW I never use the light but just listen for the spark to set timing. It's quite reliable and simpler.