Also after you get it up and running...
(ass-u-me-ing you have a tuneable distributor)
It should come with a half dozen different color springs. You mix and match these to get the desired "curve" you want, for the mechanical advance in the distributor. Or the nice modern ones, just have a dial you turn on the side of the housing... cheaters!
Anyhow, you can put it on the dyno, on the strip, use the seat of the pants, whatever...
Say you have 10 degrees initial advance and 22 degrees of mechanical advance in the distributor, for 32 degrees total timing:
Then you bump it up to say 15 initial: you notice it idles better, it's peppier down low around town, but feels just a bit "off" on the top end or it *pings*...
Well you can use this info to tune by:
1 the motor likes more lead down low / mid rpms
2 youre on the ragged edge / a little too much up top *feels flat and pings a little*
- so you know it wants more initial timing, but you're a little overboard with
37 total (you had 32 but then you added 5 more in initial)
- so change the springs in the distributor, or dial back the dial on the side of the housing, whatever you have... so that you only have say 20 degrees of mechanical advance in the distributor and leave the 5 extra degrees of initial advance in.
Now the motor will have the extra initial lead that it seems to want, but you've backed the mechanical advance off a bit so that your total timing is not so high.
- you come out with 15 initial, 20 mechanical in the distributor for 35 degrees total timing. (plus vacuum advance if you have it)
The reverse of the above is also true, if you need to just apply the same principles in reverse.
If you do have vacuum advance that's tuneable, that adds another variable... but for the most part it will only be noticable in two ways:
1 if it pings on
light throtle acceleration, or pings
momentarily while transitioning from light throtle cruise to acceleration. (a little too much vac adv, back the vacuum advance off maybe 4-5 degrees)
- *some of the vacuum advance units have a little-teeney-tiny screw inside the hole where the hose goes on, that you can turn to adjust how much advance it adds*
2 if your gas milage sucks just as bad as it ever did without any vacuum advance... or your milage is equally bad wheather your in town or on the highway. ( not enough vac advance / not working at all, check to make sure it's hooked up, diaphram not blown, etc... )
Again, hope this helps somebody.