What's the effect of timing change from 38 to 34 BTDC? Please don't ask me to read Larrys post (I have numerous times). My real question is which way to advance/retard for power if it doesn't ping? Thanks all. Cheers, Mike
Going from 38* to 34* is retarding the timing 4* As you advance the timing you are speeding up the point at which the air/fuel mixture is ignited at the top of the compression stroke. If you advance it too far then you will begin igniting the mixture before it has had a chance to be fully compressed, pre-ignition...pre-igniting...pre-mature...pinging. The piston hasn't reached the top of it's stroke so the power output of that cylinder will be reduced, and all 8 cylinders are going to react the same way. I was just using one as an example. Without a timing light if you advance an idling engine too far you will hear the sound of the engine change. The same is true if you retard a running engine too much. Neither of these are recommended. Use a timing light! The general consensus is that 34 is where you want to be. Higher than that and you run the risk of damaging the pistons, bearings, etc from detonation that you might not even hear. Not sure I answered your questions in a clear enough manner but I hope you get the idea. If you've read and understand Larry's thread you should be fine.
there is alot that goes into the sweet spot for timing, and every motor is different. head design, pistons, compression, fuel being used, altitude, humidity, all can and will effect the sweet spot. in our motors, on pump gas, I would say almost 100%, of the time, with an iron headed motor, 34 would be better than 38
And to top that off all too many people Crank in there mechanicaly advance too fast and then wonder why the motor pings, or worst yet knocks!
The motor is less likely to detonate on pump gas, detonation you might not hear. For an all iron motor, it is best to stay in the 30-34* range as Buick engineers intended. Unless you are intent on fixing it until it breaks.
I think quite a few people smarter than me have spent a lot of dyno time and drag strip runs proving that all in 34° is pretty near perfect for a big block Buick.
No one mentioned what ignition system is being used. I ran a Hays S4 system and set timing at 38 degrees on a low and high compression motor. It retarded the timing 1 to 1-1/2 degrees per 1000 rpm. There are ways to safely give great bottom, mid and top end. Today’s electronics makes it better with more adjustments.
