scottland

well after installing timing tape on my balancer, i found out that even up to 3400rpm i am getting no mechanical advance at all.

Keep in mind this is a brand new Summit HEI distributer that i bought about 8 months ago.

with the vacuum advance plugged, at 3400rpm i am still only showing 14* advance(my initial advance).

so i installed the lightest springs that came with a spring and weight kit I bought, but, i still got no mechanical advance.

so i took the distributer out to take a look at what the problem was, and what it seems like is that the arms on the weights won't fully turn the ceter plate unless you pull on the weights REALLY hard, then it will almost snap the center plate fully open.

so it seems as if the weights and center plate were poorly machined. So either way, the little mr. gasket kit i bought came with weights and a center plate, so i gave those a try, and it does an even worse job turning the center plate.

so here is some pictures, and a movie that shows what it does.

weights closed.


This is as far as it is easy to pull the weights open to.


Here is where the center plate is fully turned(full advance) but it takes A LOT of strength to pull it this far open with the springs installed.


and here is a movie of me opening it (3.9mb, quicktime)
http://members.***.net/scottland1/P1010009.MOV

So can anyone help me out here? any ideas how to get the weights to easier turn the center plate, or where to get the right weights and center plate?

70BuickSleeper

If the weights are moving, its probably fine. If the distributer is in the car, you prolly cant move the center much anyway because thats connected with gears down to the cam. Are you sure your timing gun is good? put it at idle - or below - possibly down to like 600 rpm, and set the initial timing - ie turning the distributer a few degress to get your initial. Then lock it down, bump up your rpms to 2500-3000 and you should have your initial timing - lets say 12 degrees plus the advance the distributer has built into it lets say 24 degrees, so you should have about 34 degrees of timing at around that rpm - without the vacuum advance. Are you sure you have the right rotor on it - maybe thats holding the weights in. Just take a slow look at everything, its always something easy and stupid that gets us.

chevymad

The center plate has the distributor shaft attached to it, the plate with the springs attached slides over the shaft and rotates seperatly. Your's appears to be binding. The plate should snap right back with spring tension. To fix this you need to pull the distributor gear off then pull the shaft out of the distributor. . then work the plate with hte gears off of the shaft. Lube it up well. If it's a new distributor i'd just send it back though.

A little confusing, but if you pull the shaft out, I think you'll see how it goes together.

scottland

I've been trying to slowly look at it.

the timing light works fine.

I had the inital timing set to 11.5*-12* and that was set at like 550rpm. nice and low where i know the advance won't be kicking in yet(with the medium springs).

then after tightening down the clamp, checking the timing with someone in the car holding the rpms at 3400rpm, i'm showing almost no advance, maybe a degree at the most. still about 12.5-13* advance(obviously with the vacuum advance disconected.)

the weird thing is every once in awhile the advance will suddenly come in while im driving at WOT but then as soon as i left off the gas, it's no longer there.

as for the shaft binding, with the weights and springs removed, the center plate moves very freely with no binding at all. so i don't think its a problem with that. and its the square shaped plate that is attached to the cam gear.

So the only thing i can think is that something is wrong with the weights or the cam. when i slowly pull the weights open with the springs on, the cam doesn't follow a smooth motion. it moves alittle bit like in the second picture, then it takes A LOT of pressure to pull the weights out alittle bit where the cam finally moves to picture 3. So to me it seems like the weights are never advancing it past picture 2 when the distributer is in the car.

The distributer has always done this, its just now that put some timing tape on the balencer and figured out exactly what is going on.

So to sum up my questions.

1) Is the center plate and weights installed correctly in the pictures?

2) Should it be that difficult to pull the weights open to get a cam to fully turn, even with the lightest springs installed?(it looks easy in the movie, but with the springs on, it is like 20x stiffer)

3) Has anyone else had this problem? and if so, what did you do?

If i can't figure it out by monday, i'll just go to a local junkyard and pick up a bunch of weights and cams out of a few HEI's there and see what i can do with those.

thanks for all the help in advance, i know its a lengthy read.

70BuickSleeper

The pics look out, I mean its really a basic thing, the weights and springs. It really shouldnt be hard to move the weights around a bit, they should be pretty free, if the distributer is out of the car you will be able to figure out how much the weights can pull on the center to move everything. Maybe there is something wrong with the HEI Module in the distributer. Are you getting any mechanical advance between idle and 3000? You can call up summit anytime, they seem to know their stuff, plus, if its broken, they'll set you up with a new one.. hopefully free. I hope this helps a bit, If i have time tomorrow, Ill take a look at one of the distributers I got laying around and Ill get back to you.

scottland

yeah its too late now to crank up the car(10pm.) i don't want my neighbors to hate me.

i checked to make sure that the weights aren't interfering with the rotor.

with the springs on, the weights are really easy pull out like they are in the second picture. nice and smooth.

then it takes a ton of force pulling on the weights, then the center plate snaps fully open, like it is in the center picture.

i don't know, i'll see what happens when i install it in the car tomorrow.

sqzbox

The fact that the weights move at all confirms that they work. The increase in pressure that you feel after the easy part is you trying to force the vacuum diaphram (and diaphram return spring) open with no vacuum assist . I think the weights are binding under the rotor with it installed. Try to find a way to pull the weights out with the rotor on and see if they still open freely.

AM Racer

How about a dumb idea.
Pull the distributor and chuck the bottom end into an electric drill chuck. Then you can spin it up with the cap off and see what it's doing under it's own dynamics.

sqzbox

Is it just me? Or do those weights look like their on backwards?

thirdgen88

Well, I have some input on this subject.. I got a brand new mallory coil in cap vac advance HEI distributor for my other firebird about 3 years ago... I ran into the same problem as you... I finally went to the junkyard and picked up a stock set of weights and center plate (the weights were close to the same, but the center plate was slightly different). Everything worked great from there.. I, like you, spent much time trying to figure out why it didn't work (even though it looked like it should)..

RB83L69

Looks to me like that cam & those weights are incompatible.

Put the stock weights back in that came with the distributor, and see what happens.

scottland

Those are the stock weights and center plate and came with the distributer, But then again its a Summit piece, so i would take that with a grain of salt.

UPDATE: Well this morning i put it back together with the summit weights and the mr. gasket center plate(they seemed to work the best together, and now with my initial at 16* im getting about 10* mechanical advance(26* total) The engine doesn't feel nearly as lazy, but it still doesn't pull as hard as it should (10* retarted total timing) and with the vacuum advance hooked up, i get about 40*

so i think i am going to a junkyard and just pull a whole bunch of weights and center plates so i can get the right one.

If this summit distributer on came with about 10-12* mechanical advance, thats pretty damn lame. But in the details about it on their site, they said it made more power than gm's dist. that came on the ZZ3, so i don't know,

Junkyard next......

Vader

Given the limited ability to guess based soley on the photos, it appears that the advance weights are not even contacting the cam plate in their "at rest" position. Is that true?

scottland

yep, true.

and those are the stock weights and center plate that came with the distributer.

when i go to the junkyard, should i look for weights and a cam like in the picture you posted? or are ones like that only for points distributers?

Vader

That's a stock GM Kettering distributor. I'm guessing that the cam plate and weights for an early HEI distributor may be different.

scottland

WTF.

Well today, i took off the light springs, and installed the heavist advance springs. Well my timing was set to 16* initial, and to no suprise, my initial timing dropped to 8* BTDC. I had figured that the weights were advancing some at idle.

but the weird thing is, with the vacuum advance hooked up, even opening up the throttle just alittle bit timing jumps from 8* to 45*

?!??!??!??!??!

i double and triple checked it. as soon as the throttle opens, WHAM straight to 45*

i don't know of any vacuum advance that will add 35* timing.

so what gives

Damon

Um, Scott.......

The centerplate is on upside-down. Remove it, flip it over and reinstall it. Problem solved.

You're welcome. Have a nice day.

Remember to reset you initial timing becuase it's going to be way off after you flip the centerplate. And put the original (heavier) springs back in when you do this. Trust me, this is your underlying problem. Your distributor will act more "sane" once you do.

scottland

alright, i'll give it a try.

thats was just the way the center plate came in the distributer from summit

scottland

Thanks Damon!!! Thats exactly what it was.

With my inital up to 18* so i have about 36* total timing now in by 3200rpm.

runs awsome. Thanks!

sqzbox

I've always had good luck with the med wt. spring's. The light one's don't retract the weight's good enough and the heavy one's hold them back. Have you tried the med one's yet?

scottland

no, not yet. i'm only getting about 14* mechanical advance. so i might try to the med. weight springs. i might still be getting advance at idle with the light weights.

i also heard somethng about using one light and one medium.

sqzbox

Don't do it! Keep them the same. The med. will let the adv. in a little sooner so you might have to run good gas or knock a couple of *'s out of the initial timing.

Damon

You're welcome.

I have heard that the Summit HEIs only give about 14-16* of centrifugal. I've used that distributor several times but I never bothered to check the advance curve becuase they were basic "get it running reasonably well" kinda installs and I never went that in-depth with them. Stock weights, centerplates and springs from a factory HEi will drop right in, if you want to play with it some from here.

If that's true I wouldn't bring it in much faster than the stock springs. Your initial has to be set rather high to get ~36* wide open, which means you've already got quite a bit of timing in the lower RPMs (especially when you add in the vacuum advance). Bringing it in much quicker might well cause low RPM/part throttle detonation.

But, like everything with modified engines- try it and see. The motor will tell you pretty quick what it likes and what it doesn't.

AM Racer

On my own beasts, when I mod the curve to come in quicker and add more initial I've found that the vacuum advance is more of a hassle than a benefit so I just plug it off.