Dual Distributor Belt Replacement

Contributed by:
Brian Smith 
Visit Brian's web site at http://www.brianandkrista.net/porsche/



Sadly, our 3.6 engines with their dual spark plug set-up suffer a relatively common problem. That little belt that keeps both distributor rotors in synch with each other tends to fail, causing the secondary distributor to stop turning. This can cause anything from minor performance problems to severe engine damage depending on where the second distributor stops and probably a host of other factors. Regardless of how serious some say it is – or how minor it could be – it is a problem that must be corrected without delay. 
 

Symptoms

I have had two distributor belts fail. One when I first got my 91 C2, the other when I first got my 95 C2. In both instances, the engine ran ok, but suffered from moderate to heavy pinging under load – especially at higher rpm's. Symptoms could vary widely, but any sort of underperforming engine or pinging/knocking noises could be attributed to a potential failed distributor belt.
 

Diagnosis

There are a couple ways to verify operation of the belt. First, remove the secondary distributor cap and see if the rotor spins freely. If it spins – at all – the belt doesn’t have a hold of it. The other way is to remove the input plug from the top of the primary distributor cap, forcing the car to run on only the secondary distributor. If it starts and runs – no problem. No start, no belt.
 

Prerequisites

This job is technically straightforward, but introduces a lot of possibilities for you to hit "snags." For this reason, you will need a solid compliment in the tool department. These will include:

Full metric socket set with ratchet extensions. 
Screwdrivers. 
Patience. 
Drill with various small metal cutting drill bits. 
An extra pair of hands. 
A good jack. (Not your little factory jack.) 
More patience. 
Good jack stands. 
Vice grips - possibly. 
Possibly a steel shaft and hammer to "coax" the distributor out. 
A clamp to span the length of the main distributor shaft. 
Allen wrenches. 
A refill of patience. 
Needle nose pliers. 
Dremmel tool with cutting/filing bit. 
Steel wool. 
Sandpaper. 
Bearing grease. 
Of course, the parts you need are the new distributor belt and a new, 5/32" compression retaining pin.

Step 1 – Preparation
 

Before you remove anything, you will want to get your engine ready to have the distributor yanked out. You need things prepped first so that you can reinsert the distributor later at the same place in the firing rotation as when you pulled it.
 

Remove the heater blower motor and related ductwork to give yourself some room. 

Remove the distributor caps. Leave the rotors in for now and do not take the spark plug wires off of the caps. Also, be extremely careful when removing the screws holding the caps on. The lock washers on the caps are extremely good at their job. Do not strip the heads off or you’ll have to drill the screw heads off. 

Rotate the engine clockwise by the fan pulley bolt until the Z1 indicator mark lines up with the mark on the fan housing indicating that the engine is on TDC#1. Be careful though, Z1 comes by for TDC#1 and TDC#4. See the picture below showing the Z1 mark on the crank pulley.

Remember that whole two-stroke engine thing – the crank rotates twice for each combustion cycle, but the distributor only rotates once per cycle. Confirm that you are on #1 by the position of the primary distributor rotor. It should be pointing towards the notch on the outer rim of the distributor housing. If the distributor is pointing at #4, just rotate the engine one more turn. Once you are confident that you are at #1 and the rotors confirm this, go ahead and pull the rotor caps and dust shields off the distributors. 
 

Step 2 – Removal
 

Remove the 13mm bolt holding the base of the distributor down - shown below. (Also see where you can do a visual inspection of the belt at this point.
 

Pull the distributor straight out. 
 

Note: Removing the distributor can be quite difficult, or it could slide right out. In my case, the shaft did not want to come out to save its life. The explanation was that a vacuum builds behind the shaft. Hopefully, the shaft will come out with some degree of force – pulling with your hands. In my case, I ended up drilling a hole directly beneath the distributor housing and using a steel rod to punch out the distributor from below. Just be careful and use sound and safe judgment so as not to damage the distributor or anything else.
 

Step 3 – Disassembly
 

This is decision time. Crack it open or ship it off to be rebuilt? As of now, you can get a pro to rebuild your distributor for around $170 plus shipping. Calculate your own downtime for shipping and repair. Unless you just really want to tackle this on your own, this might be one of those jobs that is worth having someone else do for you.
 

Additional Disclaimer: I would strongly advise that unless you are quite experienced in mechanical work, you do NOT attempt this DIY. You can run into snags during this process, worn parts, and severe difficulties getting things lined up properly for reassembly that can cause damage to your engine if not done correctly. Also, you can easily expect this job to take anywhere from 4 to 12 hours depending on where and how bad you get stuck. For a lot of people, this just isn't worth the price - judge for yourself.
 

Still here, ok then. Get a tall glass of ice water – no beer, you need all the help you can get.
 

Drive Gear removal: At the base of the primary distributor shaft is the drive gear, which is secured in place by a steel retaining pin. This pin is a very soft steel that crushes and mushrooms out at the ends to prevent it from sliding out. Just drill this pin out completely and don’t mess with trying to punch it out – it just mushrooms more on impact. 

Once the pin is out, some pressure will release that causes the gear to slide out some. You will need to continue to pull the gear off of the shaft. Note all washers that are on the base of the shaft for future reference during installation. 

Connector plug removal: Pull the retaining clip off of the electrical connector plug on the inside of the distributor body. Pull the plug out and using needle nose pliers, remove the connector from the black plastic housing. Push the connector and wires back into the body of the distributor. 

Primary shaft removal: Remove the 3 phillips screws from the primary distributor body. Once removed, the distributor shaft should pull straight out the top. Again, make a special note of the washers, locations, and positions so you can put them back in the same order. 
 

Remove Secondary Shaft Cap: Using a Dremmel tool or similar, file down the 3 places on the bottom of the secondary distributor housing that secure the brass plate in place. Gently pry the cap off. Be very careful not to destroy this cap. It might seem tight, but get a knife blade or similar underneath that brass cap and simply pop it out. It's got to go because that secondary shaft won't move until the retaining clip underneath it is removed.

Remove Secondary Shaft: Remove the retaining washer from the bottom of the secondary shaft and slide the shaft out. Finally, check those washer positions again.

Distributor Housing Separation: Remove the 5 allen head screws holding the halves of the distributor body together. Be very precise in removing these as they could very easily be seized and tend to strip. Get the allen key well inserted into the sockets and turn very carefully. I popped all 5 free first before removing any – just to be sure. 

There will be two pins that provide some tension and align the halves together so you might need to use a screwdriver blade to gently pry apart the two halves. 
 

You should now have your distributor fully disassembled. At any point in this process, your old belt would have fallen out. Hard to believe that one little belt was given such a critical job.
 

Step 4 – Cleaning
 

Check for any rust or pitting along any of the shafts or anywhere on the distributor. I used some steel wool to lightly buff any imperfect surfaces.

Check for proper operation of all bearings. On the top and bottom of both distributor shaft housings are small bearings. Make sure the silver wheel spins freely and smoothly within the black retainer. The bottom of the primary distributor has a different set of bearings than the top and the secondary distributor.

One shaft at a time, clean an re-lubricate each shaft and its components. Carefully noting how all washers are located, remove all washers and the belt drive sprocket. Thoroughly clean and wipe down all parts and the shaft. Re-grease all parts and reassemble the shaft. Note the four bearings and primary points needing re-greased indicated by the yellow arrows below.

 .   
 

If you have a seized bearing like I did (highlighted in red in the picture above) you really need to replace it completely. I have yet to replace mine, but I did refurbish it to the extent that I could. If seized, punch out the bearing disc from below. I used brake parts cleaner and some rust buster spray to loosen the bearings. I also had to sand all rust off of the bearing disc. I used steel wool to thoroughly clean and smooth out all parts of the bearing as best as possible. Once you are satisfied with nice, smooth operation, thoroughly grease the bearings – packing up and underneath each bearing to ensure full coverage. Work the bearings around to verify operation and smoothness. Tamp the bearing disc back into place and again verify that it now spins freely.
 

Step 5 – Assembly
 

You really can’t quit now. And besides, you’ve come this far, you might as well have the fun of now solving this puzzle. It helps to have the base of the distributor in a vice for this process as it doesn’t exactly sit in a nice, stable position. (Ready for reassembly, shown below.)

1. Insert the new belt into the base and bolt the case back together with the 5 hex screws.

2. Insert the primary shaft down into the housing and wrap the belt around the drive gear.

3. You can’t exactly slide the second shaft – gears, washers and all – into the housing at this point because the belt is in the way. You will need to slide the stack of washers and the belt drive cog off of the secondary shaft and place them inside the distributor body with the belt around it.

4. Notice the notch in the belt drive cog. This is the woodruff key that locks into the shaft of the distributor. That notch is also exactly opposite of the notch in the top of the rotor. So if you have the notch in the top of the primary rotor pointing at the TDC#1 mark on the distributor body, you will need the belt drive cog exactly opposite of the TDC#1 mark respectively. Once you feel confident that the drove cog is lined up properly in respect to the primary shaft, pull it tightly into the belt so it does not slip. It helps here if you insert a screwdriver or pin from below so that the drive cog and all the washers stay put. You’ll see why when those washers start sliding around.

5. Insert the secondary shaft into the drive cog and stack of washers that are properly lined up on the belt and down into the distributor shaft. This is not easy and make sure that your wife is not in earshot to hear you cursing up a storm in the garage. You will need to wiggle the shaft around to pick up all of the washers and to get it through to the distributor body – all while not losing the alignment you have on the gear cog. Once you get the shaft fully inserted and locked onto the gear cog’s woodruff key, you will need to check alignment again. Insert a pin or screwdriver of some sorts to make sure that both shaft notches are in exact alignment towards the TDC#1 mark. The notched belt helps to some degree – but expect to have to do this a couple times.

6. You can screw the 3 phillips screws back into the primary distributor housing to initially secure the primary shaft from sliding back out and off of the drive belt. Make sure you work the 3 prong cable back out of the body to hook up to the connector plug later.

7. Carefully holding the distributor so that both shafts do not fall out, turn the unit upside down. Reinstall the retaining washer on the secondary shaft. You might need some compression to get enough clearance to get to the groove on the shaft. You might also want to use a punch or a screwdriver blade to make sure the retaining clip fully snaps into the groove. If this retaining clip isn’t fully secured, the whole shaft will pull out whenever you try to remove the rotor – not to mention the float during operation.

8. Reinstall the drive gear on the primary shaft and use a 5/32” retaining pin to secure the gear to the shaft. You will need a clamp to compress the gear to the shaft because of the tension of the washers. You might also be able to insert a tapered punch in one side of the hole to align the gear with the shaft hole and insert the retaining pin from the opposite side. Punch the pin in place and make sure that is has fully mushroomed or expanded to lock into place.

9. Reinstall the black plastic connector to the wire plug and install the retaining clip to secure the connector plug.
 

You should now have a fully reassembled distributor. Check that turning the drive gear at the bottom of the primary shaft turns both rotor shafts smoothly and accurately – with both rotors properly aligned to TDC#1.
 

Step 6 – Reinstallation
 

You are almost home free now.
 

Insert the distributor back into the engine. Notice how the rotors turn as the gears engage. Make sure that when fully inserted into the engine, the rotors are both pointed to TDC#1 – along with your engine. You might need to pull, turn and reinsert the distributor a couple times to get the right tooth meshing on the gears to get this lined up right. 

Reinstall the 13mm retaining bolt to secure the distributor. 

Replace your distributor rotors and caps. (This would be a good time to replace them since you already have them off.) 

Reinstall the heater blower motor and ductwork. 

Plug in the connector to the distributor and reinstall the vent tub from the heater duct to the distributor vent. 

Double-check that everything is properly connected and secured. 

Check again, including a verification that all plug wires got reconnected in the right order – especially if you replaced caps. 

Start the car and enjoy all 12 plugs firing. 

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