Help setting up MSD dist before I drop it in

[GearAddict]

Ok... I've had this dust sitting around for a while and I think it's time to drop it in.

Dizzy in question is a MSD Pro-billet pn 8386 with vac advance can.

Engine 383, MP Purple 509 cam, low vac (7-8" at 950 rpms)

Currently running 18deg btdc initial timing

I've done a little reading and it sounds like....
1 blue & 1 Silver advance spring
Black mech stop bushing

What about the Vac advance? Lock it out or keep it? Anything special to do on setting it up with pulling such a low vac at idle?

 

[lewtot184]

i'd use the vacuum if possible. see if it's adjustable. usually they take a small allen wrench, something like 3/32", inside the nipple. on mopars clockwise on the wrench brings the advance in sooner and counterclockwise later. it's probably a GM vacuum unit. i'd use the largest bushing in the kit and try a pair of the lightest springs first.

 

[440ronnie67]

1 blue and 1 silver is in mine!

 

[snakeoil24]

use the vacuum advance, draw vacuum below the throttle plates, for manifold vacuum. Vac can only works at part throttle.

 

[GearAddict]

I see the "Blue + Silver" springs combo referenced a lot... 1 question though... there are "light" sliver and a "Heavy" silver springs included in the kit for the dist. The heavy ones come on the dist stock and the light ones are in the bag.

blue and light silver = very fast advance (full advance by 2250 RPM)

blue and heavy silver = medium fast (full advance by 3000 RPMs)

2250 seems way to fast?

 

[lewtot184]

having the total in by 2250rpm is not "very fast". very fast is 1200-1300rpm, or at least it used to be. you'll find that your 383 with that cam will want the timing in very quick.

 

[451Mopar]

That is what I would start with. Black bushing, least mechanical advance, most initial advance, and the springs should bring total advance in pretty quick.
Use the vacuum advance. If the vacuum advance has the internal hex screw, you can adjust the diaphragm tension to adjust how much vacuum it takes to pull the vacuum advance in.

 

[GTX MATT]

Lewtot is right, but it can be difficult to get the timing in that fast without having it bounce at idle. IMO, you would be best to call Don at FBO and get one of his 10 and 14 bushings so that you can run more like 24 initial, as the engine will probably like that better.

Check first to see if it idles better with more timing, it likely will.

 

[GearAddict]

Thanks guys... appreciate all the input.

What's the best way to check if the Vac advance needs to be adjusted? MSD instructions are no help on this

 

[GearAddict]

Can I replace the advance bushing without pulling the center shaft of the distributor? It seems like a pretty tight space to get the old bushing out.

 

[sleepar]

use the vacuum advance, draw vacuum below the throttle plates, for manifold vacuum. Vac can only works at part throttle.

This is a thread all on its own.... I use the ported vacuum on stockish setups and mechanical only beyond that but it's another animal altogether... manifold vacuum will work when the engine has minimum vacuum from a hot cam and it will act like the ported vacuum... not to start anything but there is no right or wrong answer...

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Can I replace the advance bushing without pulling the center shaft of the distributor? It seems like a pretty tight space to get the old bushing out.

The shaft should be pulled and Mark it so it goes back in with the same free play or it can bind up...

 

[GearAddict]

Digging up an older thread.

I've got the timing set at 18 initial 36 total, but the car seems to like 22 initial better, but that puts me at 40 total and I can't adjust limit the advance any more than 18+ with the bushings provided. Is this ok? It doesn't ping.

Also, I have the vacuum adv hooked up, does this add on top of the total timing or does it go away when the under part throttle, like holding steady at 3000 rpm or am I in danger of it advancing too far?