Featured Technical No mechanical timing advance

Hey guys,

My question is related to an HEI on a 455 Buick but I figure timing is timing .

Checking the timing with a new good quality timing light, I'm getting the same advance from 600 to 2,600 rpm. It seems as though I'm getting no mechanical advance. After the discovery I recurved the distributor with an MSD medium setup (picture below), same result of no change through the range. Other than trying the heavy and light springs, I'm at a total loss.

The weights move freely under the cap and the advance moves freely. I have tried three weight/spring setups now with the same result. Balancer is new, cap and rotor are new, coil and contact are new. The distributor and guts are new with less than 1,000 km.

Could there be something wrong with the pickup coil?

I'm at a loss. Thoughts would be great.

It spins clockwise, same as a SBC. The second photo below is the weights before I recurved it.

 

I could be crazy, but I think the weights are on it backwards. If it spins clockwise, those weights are not gonna be very prone to sling out. I think. It looks like a reman distributor as the parts look like they’ve been sandblasted.

 

The pickup coil moves with the vacuum advance.
Distributor advance is not one of my high knowledge things but I have seen some GM distributors with the back side of the advance weights worn to the point where they want to hang up and not move right. That was on one with hundreds of thousands of miles though. That chart is pretty explicit in that you don't get the advance with the heavy springs that you do with the lighter springs.

 

It looks like one of the weights is sitting on top of the other and that would keep the advance mechanism from working.

 

Is the MSD picture also wrong? I'm not being sassy, I genuinely am curious.

The weight installation matches the HEI I have on my bench that just came out of a SBC
Wouldn't hurt anything to swap it and try it, I guess.

 

https://www.hotrod.com/how-to/back-basics-recurve-hei-distributor

The photos in this article agree with you.

 

Check to make sure the Vac moves
With finger , it can limit the plate
Movement of wights,

& pics show opposite of @Moriarity point weights ,my self not @ shop to check 1 of 10 HEI's I have

 

No, it's not.

 

That looked suspicious to me too. When the rotor is installed I wonder if it could put the advance mechanism in a bind.

 

I'm able to move the weights freely with the rotor installed., everything is well lubricated and moves freely.

 

Yep, it advances the magnetic ring attached to the shaft.

 

Not over lapping

 

Nope not at all. Besides, my weights now look like the picture in the MSD instructions.

 

I missed typed , Mint to say
NO , not over lapping ,pic was to shown that where Not

 

Oh, yeah I got that. I was agreeing with you.

 

All good. Strangely when I spin the one on my bench (SBC, same direction of rotation), the weights fling out when I spin it counter-clockwise but not clockwise. I'm so confused.

 

Pickup coil turns counter-clockwise with vacuum applied. Mechanical Advance advances the distributor shaft clockwise. These directions make sense for advancing timing.

 

Have you done what Moriarty said and check you can turn the rotor arm? It could be something on the bottom of the rotor arm is fouling the weights. Other option maybe the springs are so light it’s getting full advance after you start it, I run my race car like that.

 

Yes, the rotor moves freely, and the weights move freely under the rotor. I did say that originally too.

There is no binding. Short of trying the lightest and heaviest weights, I'm at a loss.

I've tried three different spring/weight combos with no difference so far.

 

When you move the weights/rotor can you see the trigger moving in relation to the pickup?

 

Yep, the trigger ring on the shaft moves clockwise (advance) relative to the pickup side. That's why it's so strange to me.

When I provide vacuum to the vacuum advance, the pickup turns counterclockwise, which I believe would also advance the timing.

There's obviously an issue but everything seems to operate as it should.

 

My MSD with the two lightest springs will flutter back and forth, really messing up the timing. Maybe be a vacuum thing? Try plugging it off then run just initial and then your mechanical.

 

The timing checks were with no vacuum connected.

I'd love to run mechanical advance, but it's not making any.

 

Try using a different timing light?

 

If the weights are free and the rotor will move when you attach it and move the trigger ring; then I think that your weights are at full advance at 600 rpm. That's the only thing that makes sense. Need stronger springs.