Ignition "curve"
 

The box i recieved had a note and a Mallory distributor in it!
(thats nice as some of the boxes we have has no note )
The note says , i am not happy with this distributor , configure to match my engine application.
Pretty fair request i guess. A brief inspection finds the lower drive gear to have way too much clearance and a quick spin on the machine shows what is shown below as the "black advance curve" . Also it doesnt want to rev up with any rpm and has intermittant spark scatter above 3000 rpm. A little visual and we see the top of the ignition contact on one side is bending up and down at rpm. The rivit holding the contacts together is loose and there is a gap from time to time at speed. WOW cant say i ever seen that and feel glad to have caught it when we did. This will require a new set of contacts!!
Remove the drive gear and we find both adjustment tabs bent way too far outward. The Mallory is very adjustable without ever changing the springs etc, there are two springs , a heavy one ( loose at idle) and a light one for low rpm response. In this case the heavy spring tab was adjusted for tension at idle causing no advance on the low end of the curve at all.
A quick adjustment of the springs by feel, some spray lube , reinstall and clearance the drive gear , a new roll pin and lets run it again.
Walla pretty close this time with no rpm flash all the way up to 6000 rpm. A little bend of the low speed spring and we have the "red curve", which should make the customer happy with the distributor now for sure .....
A "curve" is just a blueprint to a spec to maximize the spark advance ...
Note the black curve at idle to 1500 rpm with 0 degrees advance, the red curve has advance all the way up from idle to 3500 being pretty progressive.

http://i103.photobucket.com/albums/m...ps2eddaf89.jpg

http://i103.photobucket.com/albums/m...ps428bf560.jpg

Lucky morning , enjoy , i am back to work.........:eek::D

Re: Ignition "curve"
 

I'm puzzled... Don't we want it all-in at a much lower rpm? What's the application?

Re: Ignition "curve"
 

On this one not really , usually we want all in at 2500 on a flathead engine, this thought can change with gear ratio, tire height etc. But usually 2500 is pretty good.
This engine has a blower on it and we need to push the curve to the right a bit , good response off idle and then add advance with boost....
You can play with the graph a bit and make up your own curve by drawing in a all in at 2500 rpm....
This one might like a few degrees less spark timing but its pretty hard to make a flathead spark knock assuming you are putting some fuel in the engine...i talked to the owner and he says he has never noticed spark knock with the 24 degree advance limit...:eek::)