493 carburetor tuning question
I was pretty tired last night. Once I started looking at your notes I completely agree there is an issue with the distributor.
On an MSD, use springs in pairs so the tension on both weights is the same.
Timing will advance in a fairly straight line.
There should be enough initial tension so the initial timing stays pretty much the same up to the actual idle rpm.
If the engine is idling at 950 rpm, then when its put into gear (assuming automatic transmission) the goal is the least drop in rpms. But if it does drop a little, and it probably will, its important the timing stays the same. Otherwise manifold vacuum will go down with the reduction in timing. With less vacuum, less fuel pulled through the idle systemswhen if anything it needs a little richer when placed in gear.
Something like the solid green line would be reasonable.
And then when experimenting with a little less initial, the whole advance shifts down as illustrated by the dashed line.
Leave the vacuum advance disconnected for now, but one of the reasons for using a slow rate of advance is planning for the vacuum advance to be used.
Interesting. That's pretty sensitive (1/2 turn of the screw). I'll check a 4779 double pumper next time I'm at the garage.
I was pretty tired last night. Once I started looking at your notes I completely agree there is an issue with the distributor.
On an MSD, use springs in pairs so the tension on both weights is the same.
Timing will advance in a fairly straight line.
There should be enough initial tension so the initial timing stays pretty much the same up to the actual idle rpm.
If the engine is idling at 950 rpm, then when its put into gear (assuming automatic transmission) the goal is the least drop in rpms. But if it does drop a little, and it probably will, its important the timing stays the same. Otherwise manifold vacuum will go down with the reduction in timing. With less vacuum, less fuel pulled through the idle systemswhen if anything it needs a little richer when placed in gear.
Something like the solid green line would be reasonable.
And then when experimenting with a little less initial, the whole advance shifts down as illustrated by the dashed line.
Leave the vacuum advance disconnected for now, but one of the reasons for using a slow rate of advance is planning for the vacuum advance to be used.
