Gentlemen,
Vac can on my 318 distributor broke. Trying to find a replacement, would be great if I could find one that fits at an auto parts store. Currently the arm is marked 10, its a 2642718 distributor spec sheet says 10.5-13.5 distributor degrees at 15" vac.
Distributor is on a nice warm 360 with cam, exhaust and intake, so I wouldn't mind a little less vac (thinking maybe 8 distributor degrees?) so I can run more initial timing.
What are my options here? I tried to swap cans with an electronic ignition distributor and the arms were a very different shape and not compatible.
You're fooling yourself if you think it runs fine without the Vcan.
Your mechanical timing curve, after you have it dialed in is only right, at best, twice; Once at idle and then at WOT after ~3600rpm. Under ALL other situations, it is dead wrong.
The Vcan can't make it perfect, but it will bring your PT and Cruse timing much closer to the ideal. On yours it should be plumbed to the sparkport, which, at idle, should have no vacuum signal at all.
Depending on your 65mph cruise rpm, your engine might like 42 to 56 degrees of timing.
Around town at light throttle, your engine might like double the timing it is getting from the Mechanical, maybe even triple depending on how far off ideal yours is, and depending on the rest of your combo.
To that end; Just get anything that physically fits, and cut the stops off the arm, until you get at least 16 or more degrees out of it; I got 22* out of mine. I think
@TrailBeast got 24 out of his.
How much your combo needs depends on how close the mechanical curve is. Mine needed more than 22, but I quit there..
Lots of initial-timing is counter-productive to setting the Transfer-slot exposure.
Your Vcan should be plumbed to the sparkport and should not affect your idle-speed whatsoever.
After the T-Port sync is set, your engine does not care about the actual idle timing,
After that, it doesn't care whatsoever the timing is until the TC stalls. If you got too much, it will tell you by either; the racket it makes, or the power-loss, or the engine parts falling into the oil pan. If you don't have enough, you won't know it until you hit third gear
At about 3600, your timing should be dialed in within a couple of degrees, else you might feel the before/after power change, but more likely you will see it in the time-trials.
The key to getting the Power-Timing right,
is to first get the Idle-timing right;
and that starts by getting the Transfer-slot exposure, underneath the primary throttle blades set right.
And finally, if you expect to get the most out of your engine, expect to be taking the D out of it many, many, many; perhaps, dozens, of times. I suggest you figure out a better way to keep the point-cam in place, instead of that miserable wire-clip. I drilled and tapped the top of the driveshaft for a small Allen socket-head screw. Then found a small washer to fit it, and finally;fabbed up a correct-height spacer. Now I can do almost everything I need to,in-situ.
