Quote:
Originally Posted by thedude327
Greg,
I'm just getting back to this thread only to find you have thrown me under the bus. Look, 12 degrees base timing is a good setting for a street engine. With his first starter damaged and his vid showing a backfire, it looks like his base timing was too far advanced causing a kickback damaging the starter. Now are you trying to compare a street engine to a race engine that may run down the quarter mile for 10 seconds under full throttle? Here's a real world example........look at the GM performance parts catalog which lists base timing recommendations for all of it's crate engine at 10 degrees. Why do they do this? Because they are want their customers to have a good running engines in their street cars without detonation. Now lets talk about what happens when you advance an engines timing, the spark occurs before the piston reaches TDC on the compression stroke. This works well at higher rpms but can cause problems at lower rpms and if too far advanced, can cause kickback during cranking damaging starters.
Paul
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Paul --
Don't take it personally -- but that is just pure nonsense. Just because GM Crate motors use some timing setting doesn't mean that's best in all cases or by default is the "maximum or minimum" timing a guy should use.
Detonation doesn't occur at idle. It occurs under LOAD... and generally from a too far advanced TOTAL timing setting. That is not controlled by the INITIAL timing of an engine - but rather - is controlled by the advance CURVE and the TOTAL timing of the distributor.
A typical MSD distributor has multiple choices of controlling the total timing and the curve. They include in their distributors (when new) stop bushings - and several spring choices - allowing the user to customize his distributor curve etc to match the engine. For an example - if a guy changes out the stop bushing to the 18* version - his distributor would have a total advance capability of 18*. So if you wanted to have 36* total advance - then the initial would automatically begin at 18*.
Timing is totally CUSTOM and depends on a great deal of factors. Head choice - cam choice - compression (really should be called cylinder pressure) - gas quality...
I agree with you that too much timing will cause problems - just as too little will do. But the oldest "rule" in the book when it comes to timing - is to run as much as possible without causing detonation. What that number is - is completely variable. And it sounds to me that you're used to only running stock distributors with stock curves in them. If that's the case - then yes - 12* would be "the max" a guy could live with because when you're advancing the initial - you're also advancing the total... and in a SBC after 36* or 38* you're in trouble..But again - that would depend entirely on what the distributor is set up for. If it has 24* of advance built in - then the max initial timing you'd want to set would be @ 12* and so on. Frankly - the best way to set timing is to set it at total - and let the initial fall where it will... and adjust your idle etc to work there. If the initial is too low or too high - then you have to modify the distributor to get you to what is needed by the application.
My new 408 has a total of 32* - it ran stronger and made more TQ at 32* than it produced at 34* or 36*. The MSD in it has the 18* stop bushing (giving it 14* of initial) - one light blue and one light silver spring for the curve control.
My brother in laws blown 355 with iron heads and blower cam - runs 30* of initial timing and goes all the way to 32* total. It's street driven and fires and runs flawlessly.
Just FYI -- back in the day (I crewed for McCulloch and Whipple) we ran 70* of timing in the nitro hemis of the day.
My only point is that when someone asks "what's the best timing"? The response would be "that depends"...