Distributor rebuild help!

[RetroSC]

I suspect my advance weight's are gummed up a bit so I dug into it this evening to clean everything up. I found something though that doesn't seem to make sense. As you can see in the pics one of the springs is different. Now I know that one is supposed to be different, but the one in the bottom photo does absolutely nothing. If I advance the weights fully by hand, there's still not enough travel of the spring mount on the large one to even start expanding the spring, so why is it even in there? This would also explain why my rev's seem to hang a bit on the way down, as the advance weight's are not being pulled in quickly enough... right?

Thought's??

[Early_S_Man]

Looks like a generic replacement spring ... one without any bend on one end. Obviously bent by hand tool to wrong length, and the MORON who did it didn't know or care that it was wrong!

Must be messing up your advance curve in a big way!

[RetroSC]

Thanks Warren! Yep, I think I've found a source of several problems I've been fighting.

Now I can bend it to the correct length, but my concern is it's so much more robust than the other spring. Will having two different spring-load's be a problem?

Bill

[jpnovak]

I have two SC distributors that have the same spring. I bent the tang out until it just made contact on one. The other is converted to a locked advance for electronically controlled twin plug.

[RetroSC]

Not sure I understand that Jamie. Are you saying it's ok to have just one spring's tension?

[ianc]

Are you saying it's ok to have just one spring's tension?

It shouldn't be, no. And the fact that you have two different springs will cause problems. Each spring has its own spring rate, so finding the correct factory ones is critical to ensuring the correct advance curve. The factory engineers have carefully calculated how much centrifugal force is generated by the weights at a given RPM, so you need the right springs with the correct spring rate for a predictable advance. Can't help you on where to source them though...

ianc

[RetroSC]

Hmmm, this should be fun!

Any idea's where to get springs like these, and how I go about finding the correct one's?

I think it's a 71S bosch distributor. Here's some number's on it if that help's any.

[Rex Walter]

You very well may have the correct springs. My originals look very similar, with one having a long side, and only comes in at high RPM. You can do a search here and find the correct advance curve. Any spring and weight combinations that give you that curve will work just fine. You don't need the correct original Porsche parts to make it work better than new. Just a dial in timing light and a generic distributor tuning kit.

Rex

[RetroSC]

So you have one spring that's not in contact like mine?

Any idea when it come's into play, mine never does. I can fully extend the advance weights and this spring is never in the game.

[Rex Walter]

The way to tell is if you get the correct total advance at high RPM. The short spring lets the advance come in quickly, which gives good acceleration. The longer spring only comes in at high RPM to limit advance (about 38 degrees at 6000 RPM I think). It is possible that your longer spring is too long, but a check of your total timing at high RPM is a good check. Some only check total advance, and not initial advance, as this is the more improtant measure for performance.

Rex

[Rex Walter]

I don't know this for a fact, but it is possible that the longer leg spring is only there as a stop for the advance weights. It is a problem with some distributors that have a hard stop, in that during hard acceleration, the advance weights will bounce off the stops and get inaccurate total advance. Porsche, being good engineers, may have added this performance advantage as a soft stop, that won't allow the weights to bounce off a hard stop.

Rex

[Tim Hancock]

My 79 SC distributor had one long spring in it also that does not make contact initially. I think it is supposed to be that way. I thought about bending the mounting tang when I replaced my bushings but thankfully I left it alone.

[BURN-BROS]

Someone will need to closely measure the larger secondary spring of a good unit in order to get the right one for you.

I believe I have a 69S dizzy 0 231 159 007
JFDR 6

If the curve is the same, I can give you the required dims.


Edit; someone could have altered the advance stop as well. Making any spring of the proper dimension useless!

[RetroSC]

Burn-Bros, yep that's the same dist and curve as mine. Do you by chance have that one handy and out of the car.

My total advance seemed ok, maybe 35 degrees or so, it's on the way down ususally around 2k that it'll hang for a bit (5-10 seconds) and then eveuntally work it's way back down to idle.

Now all this could also be a carb problem, but I'm trying to sort everything else out first.

[mb911]

My distributor had the same spring. Are we talking an sc dizzy?? ANyhow I bent the tang a little

[BURN-BROS]

Yes, the distributor is in a box by my desk. I will PM some dims this afternoon. There are a few spring manufacturers that can make what you need, you will have to buy obviously more than your requirements if they do not stock that particular spring.

If you can map your curve that you have now with a timing light,noteing the advance every 1000 rpm if possible. I personally would like to see what you have going on in there.

[RetroSC]

Thanks Aaron, I'd be very curious to find out what you have. Does anybody know what the advance curve should look like at each RPM?

[BURN-BROS]

I pulled the dizzy apart and found that it is an earlier design. So the springs wont help you, sorry. Someone has to have a 2.2S dizzy they could get some dimensions off of. Sorry I could not help

[Rex Walter]

RetroSC,

Look here for an advance curve for a 2.2:

re-curve bosch distributor

I agree with BURN-BROS, If you can show your advance at every 1000 RPM, someone might be able to give you something that will work better than your current set-up.

If your idle speed is staying up, it could be due to sticky advance weights, or a week spring that doesn't pull the wieghts back down to the idle position.

Rex