Timing not right

[Chuck2422]

I have a mild 460 build, roller conversion, 521 lift cam. MSD 6al ignition box, MSD pro billet 8477 distributor. Timing is 16 initial, 36 overall. When I have the timing light on the engine and rev it the timing advances but when the engine comes back to idle the timing stays at full advance. This only changes when I turn the truck off and immediately back on. I have changed out the MSD box, wires, grounds but the timing still advances and only comes back to initial if I turn the truck off. Anyone have any ideas?

[tnlprt]

Instead of turning the truck off ...Disconnect the power to the timing light and then plug it back in

[Ranchero50]

I have a mild 460 build, roller conversion, 521 lift cam. MSD 6al ignition box, MSD pro billet 8477 distributor. Timing is 16 initial, 36 overall. When I have the timing light on the engine and rev it the timing advances but when the engine comes back to idle the timing stays at full advance. This only changes when I turn the truck off and immediately back on. I have changed out the MSD box, wires, grounds but the timing still advances and only comes back to initial if I turn the truck off. Anyone have any ideas?

Advance is controlled in most dizzy's. I suspect the mechanical advance is sticking or has spring issues. You'll have to pop the base plate to access the arms and mechanism.

[DuckRyder]

The advance mechanism is under the rotor on an MSD, it also includes detailed instructions on selecting advance springs. It should have come with 2 silver springs and have 21 Degrees centrifugal advance in by 4000. It can be locked out so that the ignition box controls the advance, but a 6AL can't do that. (A 6AL-2 Programable can).

Assuming it is actually not returning to base timing and it isn't some anomaly with the timing light... I'd say the springs are broken or off....

Does it return to base idle RPM? How fast does the advance come in?

[Chuck2422]

Tnlport...tried unplugging the timing light. Didn't change the results. Duckryder..timing doesn't return to initial even after several minutes at idle. The most it moved after 3 minutes was down to 28 degrees. As far as how quick it is coming in I will have to check.

[DuckRyder]

What is the idle speed? Does it go down to normal idle speed?

Many years ago I had a car (not a Ford) that had a sticky advance and it would not return to base idle when the advance was stuck - IIRC.

EDIT, Also since this is a Vac advance distributor as well, Jamie may be right you may have to pull the advance plate to access that mechanism (I've never been into one of those MSD), you don't by chance have the VAC can capped off do you?

[Chuck2422]

Duckryder the advance is not capped off. It is unplugged as normal for checking timing. I will get into the distributor tonight. I have the original distributor that I will get setup as a test also. Thanks for the info. I appreciate it.

[Chuck2422]

Also the base plate is moving unrestricted. That's what is so confusing. Nothing seems to be binding. Timing just stays at full advance until you turn it off. We have the other distrib ready to test tomorrow. I will pass on the results.

[tnlprt]

I think the point they are trying to make with the mechanical advance in the dist is
The springs may not be strong enough to return the timing to initial only

[Chuck2422]

Thank you for clarifying for me. I have changed to a stiffer spring with no change.

[Chuck2422]

Update: I rebuilt the stock duraspark distributor and installed it. Once I set the timing I checked everything over and the problem is gone. I then put the MSD distributor back in and the same problem was back. Weird. The funny part is that when I had the duraspark installed I took it for a quick drive and my sputter issue under load is also gone. MSD doesn't think the issue is with the distributor.

[Ranchero50]

Update: I rebuilt the stock duraspark distributor and installed it. Once I set the timing I checked everything over and the problem is gone. I then put the MSD distributor back in and the same problem was back. Weird. The funny part is that when I had the duraspark installed I took it for a quick drive and my sputter issue under load is also gone. MSD doesn't think the issue is with the distributor.

Typical MSD...

Glad you figured it out.

[Chuck2422]

Question regarding MSD. Has anyone had a bad experience with an MSD product? I am curious as to how they interacted with you during the troubleshooting and the overall solution to your problem. I tried to provide them as much info as possible and gave them multiple chances assist in resolving the issue.

[DuckRyder]

I had a reasonable experience with them, though I did have to directly inquire if my Digital 6+ was damaged by water when they disclosed that only the beginning of production was potted (which is why I went with a digital 6, literature at the time indicated it was potted)... They have a support forum (or did) and seem to answer reasonably quickly.

Anyway, they did fix it and quickly for a reasonable fee.

I confess I'm a little confused by some of the things you've reported, though I have not been into a dual advance MSD distributor I suspect that the vacuum only advances the breaker (or magnetic trigger) plate and the mechanical advance works like any other MSD which ships with two silver springs installed. Silver springs are the heaviest springs, so I'm confused when you say you put heavier springs on.

Without knowing the exact target curve and the actual curve, it is hard to provide advice...

There are only a few things in the distributor internally that would cause this, so it should not be that hard to figure out.

[Chuck2422]

The distributor was shipped with the weakest springs installed. We were not able to fix it. MSD shipped me another one and it worked. Same setup, same springs, advance weight. MSD basically said it happens occasionally. As I said before this doesn't make sense. No visible issues with the distributor. The original engines distributor was rebuilt and even though it is not useable long term, it showed us that the issue was the distributor from MSD.