Indicators that your Distributor Shaft is worn

[Alan Lindquist]

This isn’t indication that you’re distributor shaft is worn –it’s the truth and the proof. You can imagine that the contacts inside the distributor cap are all gored out and looking pretty miserable.

Amazingly, the car ran for 20 miles like this – not well, but it did run. This is on a 1980 SC that is a daily driver with 280,000 miles on it. The cap and rotor are replaced each June when I do the valve adjustment and put in new plugs. I oil the shaft as recommended at that time. I may have to step up my shaft-oiling regime.

Before it got to this point, here’s what I was noticing in the last week to 10 days:
1. On startup there was some chirping noise that was rapid, lasted for a second or two and then stopped. I wrote it off as a loose or cold fan belt. Now I’m thinking that the wobbly shaft was centering itself while shearing the rotor tip on the contacts.
2. The car became more difficult to start when cold. Hot starts were normal. I’m thinking that the shaft was settling in an awkward spot off center when left alone for 8-10 hours.
3. The engine exhaust noticeably was “popping” on deceleration whether the engine was warm or cold (rich exhaust gasses from incomplete spark/combustion)
4. Occasionally the engine would die from a stable idle at a stoplight or with the clutch in coasting up to a stop.

Each of these things is a noticeable change from “normal” when driving the car each day. When it’s a daily driver, you note the problem in your head, monitor it, and then plan time to dig in over the weekend. Last weekend wasn’t convenient. This weekend didn’t arrive soon enough.

It takes less than five minutes to pop the hood and detach the hold down springs on the cap, inspect the rotor and cap and wiggle the shaft. It’s quick and free. So here’s me recommending that you do that occasionally and certainly each time you are servicing the engine. Better to know that your shaft is worn than to let it get this far.

New distributors are over $1,100. I found a solid used one in good shape for $300. A rebuilt is probably somewhere in-between. So keep yours lubricated!

[kach22i]

Can you post a detailed photo of the inside of the cap?

[Alan Lindquist]

Originally Posted by kach22i

Can you post a detailed photo of the inside of the cap?

Sorry about that. I thought of taking a photo but my iPhone doesn't do macro very well. The burnt resin was ALL through the cap. The contact points were gored to 70% original thickness in all manner of tracks and angles.

[GaryR]

You can send it out to someone like Barry Hershon or Jerry Woods and have it rebuilt also... Barry has some sort of custom bushing he puts on there, can also re-curve it and supply you with a plug-and-play cable to easily hook in an MSD 6AL...

[kach22i]

Originally Posted by Alan Lindquist

........ and wiggle the shaft. It’s quick and free.

Is there a wobble side to side, I don't understand?

If there is no wobble (a slight up and down is movement is tolerable) then I'd consider looking at some voltage increase which is arcing and frying the contacts inside of the cap.

Might try looking at this thread (for background information):

Distributor service (Clean and lube) real easy without removing the pinion gear!
Distributor service (Clean and lube) real easy without removing the pinion gear!

.............and this thread:

Ignition Rotor Meltdown
Ignition Rotor Meltdown

[Alan Lindquist]

Originally Posted by kach22i

Is there a wobble side to side, I don't understand?

If there is no wobble (a slight up and down is movement is tolerable) then I'd consider looking at some voltage increase which is arcing and frying the contacts inside of the cap.

Might try looking at this thread (for background information):

Distributor service (Clean and lube) real easy without removing the pinion gear!
Distributor service (Clean and lube) real easy without removing the pinion gear!

I wobbled it in the past. Yes, up and down is tolerable. I never noticed side to side in the past. But the movement that was destroying this rotor was DEFINITELY 360 degrees of "wobble" and it was significant. Unmistakable. Shaft bushings were shot.

[kach22i]

If it's shot which it sounds like then yes someone like Barry Hershon is one way to go.

I've recently seen an engine without a distributor, but I'm just learning about it so I'm not sure it's a affordable option yet.

Start reading at post #1069 .............coil packs and crankfire direct ignition systems
Engine Porn

[rusnak]

I posted a thread about this around 7 or 8 years ago I think. It's common for 1980s 911s to have worn distributor bushings. In many cases such as mine, there are no symptoms until the rotor hogs out the cap contacts. When this happens you lose spark but fuel continues to flow. The cat gets red hot and is destroyed. You end up having to either tow your 911 or buying a distributor.

I found that Porsche was doing an exchange program, selling rebuilt distributors. I ended up getting a brand new one for around $1,000 because the program was just getting started with new cores.

The best thing to do is to take off the cap and grab the rotor shaft. See if you get radial play. If you do, then you must change the bushings.

[Bob Kontak]

Originally Posted by kach22i

If it's shot which it sounds like then yes someone like Barry Hershon is one way to go.

Just a thought. If you are dealing with a pro, you could talk to him about your set-up/application and he could dial in a few more degrees full advance at the expense of premium gas. Incremental cost s/b marginal, but I don't know for sure.

SC total advance is quite wimpy and plays out quickly.

[Bob Kontak]

Originally Posted by rusnak

no symptoms until the rotor hogs out the cap contacts. When this happens you lose spark but fuel continues to flow.

Based on Alan's first post, I bet the tip was busted off from "blunt force trauma" and the 20 miles he was able to drive (limp) was allowed by some major spark leaps to what was left of the distributor contacts.

[Alan Lindquist]

Originally Posted by rusnak

In many cases such as mine, there are no symptoms until the rotor hogs out the cap contacts. When this happens you lose spark but fuel continues to flow. The cat gets red hot and is destroyed. You end up having to either tow your 911 or buying a distributor.

I'm glad you brought this up. I run a CAT bypass pipe - except for a day or two every two years when it's time for a smog check.

So I wasn't worried about a rich exhaust but it definitely would be a problem if there was a CAT hooked up.

I think the problem is somewhat progressive. I posted the indicators because I was sensing a problem but not responding to the indicators. If anyone is sensing a problem and has these indicators, then checking the rotor shaft is quick and easy and beats being stranded to a tow truck or ruining a CAT. Or ruining the distributor beyond reasonable repair.

[GaryR]

I would suggest anyone with a 30 year old, high mileage 911, to at least have the dizzy rebuilt by Barry Hershon. It will cost a few hundred bucks and you are good for another 25 years+... Just my $.02

[snbush67]

Originally Posted by GaryR

I would suggest anyone with a 30 year old, high mileage 911, to at least have the dizzy rebuilt by Barry Hershon. It will cost a few hundred bucks and you are good for another 25 years+... Just my $.02

I was quoted 500 minimum and up.

I agree that an old distributor should be serviced and checked for wear, however, I think it is well within most DIY peoples abilities. Simply measure your curve with a timing light, if you need more advance you can bend the stop tabs, install lighter springs to get a quicker response. The distributor can be dismantled and serviced with a screwdriver, hex wrench, and clip-ring pliers.

Often times the only problem with the distributors is crud and lack of lubrication. The internals are pretty tough and can be brought back to life with some elbow grease.

[timmy2]

Why not fix it yourself? I rebuilt mine for under $50, works great, following this thread:
83 SC Ignition Distributor Bushing Replacement

[rusnak]

It's easy to wreck the distributor too. If the gear clearance is off/ missing washer/ or the rollpin fails, then you can put a hole in the engine case. When it's correctly rebuilt, the distributor is good for another few hundred thousand miles. I think taking it to a pro is actually going to save you money.

[Alan Lindquist]

All points are valid here so far. DIY folks will do a rebuild themselves. I admire them. Some of us will do component replacement with something we may trust. A bit less "handy" and a bit more expensive, but we don't all have the same skills. Others will take their car to a mechanic and trust the fix. It's all good - these cars will continue down the road with any solution, which is what we all want.

But we all should recognize the indications of component failure and act "as if" we are in tune with the car and giving the car the maintenance (preventative and corrective) that it deserves. I failed my car. There were indicators of rotor shaft failure that I didn't pay attention to and a bit more curiosity and care could have been warranted.

In the end, it doesn't matter if we rebuild the part or replace the part with a suitable part or have a mechanic fix it for us. But we do need to recognize when the car is "talking" to us.

[Charles Freeborn]

Game over. Send it to Steve @ Rennsport or Jeff @ Rothsport.

[timmy2]

Originally Posted by Alan Lindquist

All points are valid here so far. DIY folks will do a rebuild themselves. I admire them. Some of us will do component replacement with something we may trust. A bit less "handy" and a bit more expensive, but we don't all have the same skills. Others will take their car to a mechanic and trust the fix. It's all good - these cars will continue down the road with any solution, which is what we all want.

But we all should recognize the indications of component failure and act "as if" we are in tune with the car and giving the car the maintenance (preventative and corrective) that it deserves. I failed my car. There were indicators of rotor shaft failure that I didn't pay attention to and a bit more curiosity and care could have been warranted.

In the end, it doesn't matter if we rebuild the part or replace the part with a suitable part or have a mechanic fix it for us. But we do need to recognize when the car is "talking" to us.

^ This...

[rusnak]

Originally Posted by Alan Lindquist

All points are valid here so far. DIY folks will do a rebuild themselves. I admire them. Some of us will do component replacement with something we may trust. A bit less "handy" and a bit more expensive, but we don't all have the same skills. Others will take their car to a mechanic and trust the fix. It's all good - these cars will continue down the road with any solution, which is what we all want.

But we all should recognize the indications of component failure and act "as if" we are in tune with the car and giving the car the maintenance (preventative and corrective) that it deserves. I failed my car. There were indicators of rotor shaft failure that I didn't pay attention to and a bit more curiosity and care could have been warranted.

In the end, it doesn't matter if we rebuild the part or replace the part with a suitable part or have a mechanic fix it for us. But we do need to recognize when the car is "talking" to us.

Well said!!

[snbush67]

Porsche Whisperer. Clint Eastwood plays a Seattle based Porsche Mechanic who talks to cars. I like it.