Featured Technical No mechanical timing advance

Have you tried flipping the weights in the opposite direction just to see what happens ? I know this is frustrating for you, but it might be worth trying if nothing else is working. If a distributor is turning clockwise, the centrifugal force should be in the same direction no matter what type of distributor is in place. Good Luck with it.

 

Looking at this image...


Those weights don't look like they are properly parked. Note the center plates shape, it has reliefs for the weight fingers.
That would set a preloaded mech advance, this also limits available mech advance, and also why there is no change in mech advance at lower rpms.
The spring studs are usually more inline as well, at rest.

Flip the weights like Moriarty posted and see if the weights park closer to the shaft.

 

Read the rest of the thread. I'm done commenting on that.

 

Is this what you're working on?
Turn the weights around.

 

I'm not a GM guy, so please help me understand.
You guys are telling me that the GM electronic HEI spins in the opposite direction then a GM point distributor? Doesn't that require the gears that drive the distributor have to be cut in the opposite direction as well?

That means the plug wires have to wrap around the cap in the other direction as well to keep the correct firing order, correct? After all these years, you GM guys don't all that that little, sort of important, fact all sorted out?

 

Gene, GM make engines like Chevrolet and the 455 Buick, in question here, use clockwise distributors, point or hei.
There are some GM engines that use counter clockwise distributors.
Looking at the distributor from the front, the former has the vac advance on the left, the letter have vac advance on the right.

 

Is your distributor a MSD Pro Billet (8365)?

 

Had to look just because. Now I’m more confused. Both CW rotation.

 

No, Gene. All SBC's and subject big block buicks rotate clockwise. On GM clockwise rotation points distributors, the big side of the weight is after the pin (in direction of rotation). On GM clockwise rotation HEI distributors, the big side of the weight is before the pin (in direction of rotation).

That's clearly not well understood, as evidenced by the MANY replies on this thread that think they're backwards.

 

It would do you well to play with the weights on an HEI. That's what they look like fully retracted. There is no mechanical advance acting as shown in the photo, and the weights are fully nested against each other (rest position).

 

I answered that yesterday. No, it's a GM HEI, not an aftermarket performance distributor.

 

This sure had me looking, so I found a GM HEI setting around and the weights are as you showed. Found a Pontiac points distributor and it had the weights like yours. Guess there is a difference between a points and a HEI as to how the weights are.

 

Your mechanical advance weights seem to have a very different shape, compared to the various photos of sbc hei distributors.

Are your weights, GM factory for Buick 455?

 

@05snopro440

Not trying to beat dead horse
Here are 2 that I was able just to lay hands on
Both are from Chevys & I just notice different shapes in the weights !!
The Weight's & advancement ring move freely and rest freely as shown.
Noticed that the weights are different, Im thinking the weight Weigh different in "Grams" ! , Op are different also !
maybe later on tonight I will pull out my gram scale and weigh the weights to see if I am correct,
Or there is a difference in the weights for Mechanical advancement in deg's.
I would like to have a distributor machine, I'm curious what different between these two and I wonder how many more different weight designs there are just for Chevy's ?
3 different shown so far in HEI

 

Damn, I was hoping someone would point out that this is one worn out P.O.S. Look at those pivot points.

 

I've had 2 that did that and had to be replaced as they were worn out junk.

 

Ok. Cool.
Just make sure you let us all know what the solution turns out to be.

 

That is a lot of hours running to wear as it has . I’m betting you look deeper into that on you will find lots worn out . I feel as you say , it’s either junk or time for a complete tear down and over haul

 

I just replaced one worn out that badly on something else. Picked up a lot of horsepower with the new setup.

 

Here's what I found:

• With the lightest springs in the MSD kit and the factory weights, the mechanical advance starts at about 1,000 rpm on my setup. It's all in about 2,500. The springs were my issue.
• I tried light springs out of a moroso kit and they came in a little later.
• It didn't like the light msd weights.
• The factory 438 center cam with the 053 weights only gives about 15 degrees of advance. I might need to see if I have any other center cams to try for a little more total mechanical advance.
• For the 11+ replies that said the weights are on backwards, and a few that said they're not at the correct position at rest, that's not correct for an HEI.
• After getting the mechanical advance working, I tried my vacuum advance on both ported and manifold vacuum. It sounded and smelled happier at idle with it on ported, so that's where I put it.
• A test drive showed me I still have a little bit of carb tuning to do, but it's 90% better than it was there are 3 150+ foot tire strips on a back road nearby that tell me I'm getting there.

For whatever reason, this distributor wants really light springs. With a different center cam it might want to be all-in a little later, time will tell. As is there's no pinging through the rpm range so it's much better than before.

 

Good to hear you are making progress.
So far what do you think was the biggest contributer that put you back on track?

 

Centrifugal force wont care which way a distributor turns to make the weights want to move outward. Or which way the weights are located to move outwards.

 

This has been a concern of mine for years. Could never find an answer.
On the chev, HEI weights always seem to be backwards compared to the points distributor.
Some early GM photo's of the HEI do show the weights the same direction as the points distributor. Later photos show them opposite direction. Same as diagrams in the early 70's Motors Manuals. GM had several designs with the support plate under the weights. Early ones were diamond shaped, later design was 4 arms. The later ones will not allow the weights to be reversed.
The advance cam can also be reversed. some had the number on the top others were on the bottom. would be nice to experiment with a distributor machine to see what difference things made rather than just trial and error.

 

....... or flip it over, as a couple of replies have suggested.......

 

For what feels like the 9,000th time, why would I install it wrong?

 

Sorry, I obviously haven't been listening.
I wasn't aware you were asking for help but don't actually need it.
Carry on........

(And, so you know, I am laughing as I post this.)

 

The cam can only be flipped if the weights are also flipped. That's the way it is run on counterclockwise rotation distributors (Olds, for example). On mine I'm (now) getting the advance I'm supposed to with that weight and cam setup so reconfiguring the weights as many have suggested is pointless.

 

I believe it would be the same story with the HEI.

Many guys have tried to claim my weights are too far out at rest or flipped. When at rest, they are fully pushed against each other in that rest position. They can't go further in. When running it, it gives the advance it should with the cam and weight setup I have. It's functioning exactly as it should, for a smog-year weight setup.

 

Exactly. GM had a reason, and I don't have the equipment to figure out why (nor do I care, since I've now learned that was how they were set up).

Centrifugal force is centrifugal force.