The MSD 8383 comes with their heaviest advance springs installed . In their kit they provide 2 other spring sets and two other bushings. According to their charts, for my appliction, getting to about 34 degrees advance at 2,400 RPM I'll need to use their lightest springs and their smallest (red) bushing. Changing the springs is a snap. Changing the bushing on the underside of the advance plate would be nearly impossible with the distributor in the motor. I think you can probably do it turning the distributor upside down, but with my stubby fingers I can't even touch the nut that holds the bushing. Anyone done this that can give some tips?

  Ron Lane,  Meridian, ID

I can see where making a bushing change in the 8383 distributor might be cumbersome in the vehicle. On the dyno where I can access the distributor much easier, it’s doable but it does take nimble fingers. With the distributor out of the engine and upside down, it’s relatively easy to change the bushing but having it out of the engine and thinking about a bushing change at the same time rarely happens on my end. I typically have always had to change the bushing with the distributor in the engine.

---

If you haven’t already driven the vehicle with the factory installed blue bushing in place, I would suggest doing so before actually changing it out. You may find that the engine will be more responsive with an increase in initial advance.

Lorena, Texas (South of Waco)

Thanks for the response Ted. I also spoke with Gord McMillan and we talked about the fact that because this is a supercharged application, maybe I should try the silver bushing with a light silver spring and a light blue spring. MSD provided the attached curve graphs associated with the different spring and bushing combinations. I set-up the distributor to the "e" graph which gives me a distributor curve of 25 degrees at 3,000 RPM. If I use 13 degrees of initial timing (giving me a total of 38 degrees max advance) I think (hope) I'll be close enough where I won't have to pull the distributor out again. Changing the springs is a snap and once I get the engine to the dyno, I figured we can do more adjusting if we have to. Below are the graphs that MSD provides.

Rono

  Ron Lane,  Meridian, ID

Ron, On the "F" code cars we run a Total of 30 degrees (mechanical). My car, with iron heads, slows down on 93 octane with anything higher. I have tried 118 octane and more advance and saw no improvement.

I'd suggest you consider 13-15 degees initial and limit the distributor to a 30 degree total. Pre ignition is not good, and 38 degrees will get you there unlees you're running alcohol or nitro.

Frank/Rebop

Bristol, In ( by Elkhart) 

Ted/Peg Leg;

I would rather be on the conservative side and not risk blowing head gaskets or worse. So if I combine both of your suggestions and reinstall the blue bushing, which spring combination should I try first? We'll definately get the motor running and broken in first before we connect the blower drive. I definately don't want to overspin the supercharger and with the high output impeller my max engine RPM is 6,000. I guess another option would be to go with the black bushing and go with either the "e" or "f" curve which would also give me a maximum advance of 30 degrees with an initial advance of 10-13 degrees. I appreciate your thoughts.



Thanks,

Rono

  Ron Lane,  Meridian, ID

Rono:
Are you planning on locking out your vacuum advance because if not you will have way too much total advance with initial of 13 deg then adding mechanical advance and vacuum advance. I had to do several changes to my MSD distributor to keep the total within limit so not to ping. I am running Mummert heads with a true 9.7:1 compression.
Here is a link to a previous discussion on a MSD distributor with a blower engine.

http://forums.y-blocksforever.com/Topic57467.aspx

marv

Marv;

I read the MSD instructions on locking out the vacuume advance and to be honest, I don't know the difference between locking out and not connecting a vacuume line to the canister. Either way, I was not planning on running any vacuume advance on this distributor. MSD does provide a plastic wedge for locking out the vacuume advance. I'm not sure if it replaces the entire canister assembly or mounts under the arm from the canister.

I've read the other from posts back in 2011 and I'm using 471 heads with forged flat top pistons (John's 331 cu.in. stroker kit with the domes milled off) and I also relieved the block. I'm thinking that my compression should be less than 9:1, but I'm not exactly sure yet. So, I'm just trying to figure a good starting point for the bushing and spring combination.

Rono

  Ron Lane,  Meridian, ID

Okay, so if I don't run any vacuume advance, is 38 degrees total advance too much in your opinion? I think I will switch back to the blue bushing as Ted suggested. I re-read the MSD instructions about removal of the vacuume canister and I agree with you that removing it would definately clean up the appearance and provide more room. But replacing with the lockout piece sounds a bit tricky and can create problems. It may or may not need to be shimmed. I'll decide one way or another sooner or later.

Rono

  Ron Lane,  Meridian, ID

Don't worry about the vacuum now, it does not work at all under boost. The advance curve can be quick because you won't see any boost until 2500-3000 anyhow. You will be able to run quite a bit of advance up to that point becaause what you'll have until the boost comes on is a low compression, small engine, that needs a lot bof advance. I have mine all in by about 2500.

Frank/Rebop

Bristol, In ( by Elkhart)