morgsie

iTrader: (1)

Just wondering if anyone can shed some light on determining base timing and idle settings. It seems for base timing everyone says to just set it to 0 or 6 or 10. Is there a way figure out what the best base timing is for a particular application? Would you use a vacuum gauge and want the highest vacuum for the base timing setting? Or is it all just trial and error, ease of starting, etc? The same goes for base idle, do you just set it the lowest RPM the engine will run at? I know for manuals you can't set it to high or you will get gears grinding when trying to put into gear initially. I've googled around and checked a few engine books I have but haven't really found any "solid" information.

Thanks.

vetteoz

iTrader: (13)

What engine?
If you have a computer controlled dist then your options are limited because the computer has spark advance control

morgsie

iTrader: (1)

My engine is a 355 -- FT piston, vortec heads, cam specs: 218/224 @ .050 113* LSA .536/.531 (only running 1.5 rockers). Not concered about the ECU as it will/can be modified for whatever base timing I set.

Cosmik Debris

The human race has advanced quite a bit in the last few thousand years but we are still not mind readers. What sort of car, is it the standard ECU for that car?

AlkyIROC

If you have a stock cam then use the recommended setting.

Typically, it's recommend 10 to 12 degrees of initial timing when the duration of the camshaft is less than 220-degrees @ 0.050” of valve lift

14 to 16 degrees of initial timing with a camshaft duration of less than 240-degrees @ 0.050”

18 to 20 degrees of initial timing when the camshaft duration is less than 260-degrees @ 0.050” of valve lift.

Advancing the base timing will also advance the total timing. You need to adjust the total timing to where the engine likes it the best. If the mechanical advance is 28* and base timing is 4* then total timing is 32*. Bump the base timing to 10* and the mechanical advance changes the total timing to 38*. Your engine may not like 38* total timing although it will probably like 10* of base timing.

The older HEI distributors could be recurved to change the mechanical advance. With an ECM controlled distributor, it needs to be reprogrammed.

morgsie

iTrader: (1)

I think I must have worded what I wanted to know wrong. By base timing I am talking about (for example) the amount of degrees set with the timing wire disconnected on a TBI/TPI car. Or in the case of HEI, vacuum advance disconnect. While it would be nice to know what to use for my setup, I was trying to get a general idea or tip on how to determine base timing for any engine.

To elaborate further: TBI engines use a base timing of 0 degrees. Would I use this setting with my setup> When would this base setting need to be further advanced for a more radical setup? Hope this helps.