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Timing advance for racing...

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Baz

Baz

Yoda
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Hope the racers can help me out here.
At the last autocross, the stock 1275 garbled a bit in the higher rpms, 4500 - 5500. The timing is set at book 15* BTDC.
I messed around and at 25*, it was a lot smoother in the higher rpms yet idled like a sick puppy.
Just curious as to what you guys are running, understanding that you have serious modifications going on, and mine is stock.
Should I just stick with 15 and just adjust it at the track, or is there a happier medium you chaps are aware of, that I haven't found yet?
TIA
 
I set it at 30' to 32' at 5000 rpm so that all the mechanical advance is seen. It will help you pick up some torque. You will probably need a higher octane to run that much advance. Drop it back a little for street driving so you don't have detonation if you are lugging up a hill.
 
At 15 degrees initial timing, if the distributor centrifugal advance is working, it should easily give 32 degrees or more at 5000 rpm.- Vacuum advance disconnected for both tests.- Check the advance with a timing light to see how much it advances at the higher rpm. If it goes to well over 32, something is going to blow at that setting. If it doesn't increase from 15 to 32, the centrifugal advance needs repair.
D
 
"the centrifugal advance needs repair" I would put a buck or two on this.
 
Hello Baz,

you say the engine is stock so the distributor should be correct for that. If you find that the advance at idle is too far advanced and that the advance at high revs is correct, then it could be that your distributor is the wrong one for your engine. Basically, unless it is tight mechanically, (forget the vacuum mechanism)then the advance curve is too short. With a Lucas distributor, the rotor has a number stamped on it which is the distributor total mechanical advance (1/2 engine advance). This can be altered by grinding the 'beak' to increase the total mechanical advance. You need to accurately measure the gap between the beak and the stop and divide by the number. Use that as a factor to adjust the overall timing spread.

Alec
 
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