i was reading one of the articles from the sticky about timing and it was talking about mapping the distributor and that you get the mapping for the centrifugal advance from your owners manual. unfortunately im not running a stock engine and have no idea what the mapping would be for my engine.

Does anyone know how i should go about determining the mapping i should be using.

The distributor i am using is the stock distributor and i would guestimate that my horsepower output is around 350.

Sorry about posting yet another timing question im just very confused.

 

im also confused about when you check centrifugal timing do i check with the vacuum advance still blocked off?

 

By mapping do you mean plotting the advance curve?

BigBlockk

Later.....

 

if you don't have the original motor and don't know how the motor was originally built, etc than make life easy for yourself and go the simple route.

1. are you running a points or HEI distributor? If it's a points unit than FIRST check and adjust dwell. Should be around 30. I set mine at 30. After checking and setting dwell at idle speed rev up motor and watch the dwell meter to make sure it stays steady. If i it varies and flucuates than your distributor has too much main shaft paly and it needs to be shimmed.
If you have an HEI you can skip this step.

2. unplug the vacuum hose off the vacuum advance can and plug it. you will probably have to bump up the idle speed if it was connected to full manifold vacuum.

3. you can now do a "simple" mapping of your distributor just to see how it's currently set up. re-read my sticky post and the references articles in it to check initial timing with the weights wrapped in a rubberband. This checks true initial timing without any chance of early mechanical advance being allowed to come in.
Wtite this number down or remember it.
Now remove the rubberband from the weights and check initial timing again.
It the initial timing figure is the same both times than your mechanical advance is NOT coming in at idle speed which is perfect.

4. Now check to see at what RPM your timing is coming ALL IN at by revving the motor up and seeing when the timing stops advancing. If it is still coming in past 4000-4500 don't bother to check at higher RPM's.
You want your timing all in between 2800-3000. If it is coming all in later than that than put in different springs on the weights so that it comes in sooner and you get no more advance past 3000rpm.
you want 36º total timing between 2800-3000rpm.

5. Once you get yout total timing set at 36º between 2800-3000rpm than you can go back and check your initial timing at idle again and see where it is. If initial timing falls between 12-16 or so than you are good to go. Just check it with a test drive for detonation and if there isn't any reconnect the vacuum advance and make sure total timing with vacuum advance doesn't exceed 52º and you are good.
If initial timing is now much higher than 16-18º than you should have your distributor recurved to increase your mechanical advance.
On most stock or lightly modified motors your goal numbers should be about :
12º initial timing
24º mechanical advance starting about 200rpm's above idle speed
36º total timing
(all this with the vacuum advance unplugged and blocked)
52º total timing with vacuum advance reconnected when timing is all in.

Also, make sure vacuum advance is connect to a full manifold vacuum source, not a ported source.
Once you reconnect the vacuum advance you will need to lower the idle speed down again.

For more details, refer back to my sticky post and the referenced tech articles by Lars and John Hinckley