Post by vanapplebomb on Jul 30, 2015 11:09:45 GMT -5
Part 1: When and why to use a DVDA distributor
In the 70's as emissions regulations were ramping up, more precise control of combustion temperatures and speeds were deemed nescesary. Various companies adopted various methods of reducing hydrocarbons. VWs response was the 34 PICT 3 or 4 on single carbed engines, 34 PDSIT 2 and 3 for dual carbed engines, and Bosch Djet/Ljet fuel injection. These systems targeted issues of slow combustion speeds and low combustion temperatures at idle, which inevitably resulted in imcompleat burning of the air/fuel. Earlier solex carburetors operated approximately stoichiometrically (~14.7:1 air/fuel) at idle. While this works great under load, the high vacuum at idle results in a significantly lower density air/fuel charge in the combustion chamber. This lower density charge burnd slow and a sizable portion of the gasses were exhausted out the tailpipe before they even had a chance to burn. The new generation of Solex carbs and Bosch fuel injection introduced the lean burn concept in 1970/71 which would eventually be adopted by all automakers come the end of the decade. The idea is that a leaner than stoichiometric charge of air/fuel (within reason) increases the oxidation rate of the fuel because each gasoline molecule is in close proximity to more oxygen, so the chemical reaction can happen faster. Immagine you are a molecule of gasoline and flies are oxygen. You are in a small room with fifteen flys. Catching them all is easy because the room is small and you are in close proximity to them (stoichiometric, dense air charge, low vacuum partial to full load). Now Immagine how much longer it would take you if you tried to catch those same fifteen flies in a large room (stoichiometric, lower charge density, high vacuum idle). So, if you wanted to catch fifteen flies in a large room in the same time it would take to catch fifteen in a small room, it would help to have more flys in the large room ( lean burn with more O2, low charge density, high vacuum idle). Sounds great, but the rapidly burning hot lean combustion will create peak pressure to early in the cycle with the standard 7.5deg before top dead center timing. To keep the system from fighting itself because of the rapid combustion, the timing needs to be retarded in order to keep maximum pressure in the cylinder partway down the power stroke. This is why you see the timing at idle for 34 PICT 3 and PICT 4 (California), 34 PDSIT 2/3, and all 71 and newer Bosch fuel injections set at either 5deg or 10deg AFTER top dead center.
These systems require a completely differant advance curve, which is why simple mechanical and earlier SVDA distributors refuse to play well with them. Engine problems that arise when using mechanical or SVDA distributors with lean burn systems depend on how the user times their engine. Time the engine for max advance at 28ish rpm, and the timing will be far to advanced at idle and the engine can sound and run like it is pinging, run very rough and hot, and may backfire through the carb because of the large amount of pressure that builds rapidly before the intake valve has a chance to close. Ok, so you loosen the clamp and twist the distributor around so it is timed properly at 5-10deg after top dead center at idle. Now you get nasty flat spots off idle and a gutless wonder up top because of a lack of total advance. A compromise between the two extremes helps little.
To my knowledge, nobody is making suitable replacement distributor for lean burn systems, so reusing the original Bosch distributors is the only option, and most here in the states are about 40 years old give or take a few, and could really use some love. Thus, the purpose of this article. Enjoy!
Part 2: What makes a good refresh candidate?
There are two basic sub assemblies inside the distributor that cause most of the problems. They are the vacuum advance/breaker plate assemble, and the mechanical advance assembly. There are other areas of interest, but those two failure points can make the difference between a salvageable distributor and a spare parts bin special.
Start with the vacuum mechanism. Suck on the nipples and see if the breaker plate moves. The nipple on the outer side should advance the breaker plate a small amount, and sucking on the larger inside nipple should retard the breaker plate a considerable amount. If this checks out, repeat the steps again, but hold the vacuum by covering the nipple with your tongue or pinching off the line if using a hose. With the vacuum held, the breaker plate should not move from its advance or retard position. If it slowly creeps back to neutral, you got a leaky diaphragm which is no good. Move on and try another one, or keep it if you want something to rob parts from in the future.
Next check to make sure the mechanical advance is not frozen up. Hold the drive dog on the base and twist on upper portion of the shaft where the rotor attaches. It should be able to rotate slightly with resistance in one direction only, and then it should snap back to its original position when released. If it is stuck, the previous owners (or you!) forgot to add a drop or two of oil to the felt wick underneath the rotor cap with every oil change, and the shaft seized onto the bushings. Although it can probably be separated, it is most likely toast anyways because the tolerance between the shaft and bushings of the mechanical advance mechanism are very precise, and any clean up work done would result in too much radial play of the rotor. Speaking of radial play, avoid distributors that have excessive radial play at the rotor end of the deal. Ideally this would Be less than a couple thousands of an inch, but these days you may have to settle for 5 thou or so. There are still a lot of good cores out there, so you shouldn't have to resort to machining and replacing bushings to get something acceptable. Don't worry about excessive axial play. The mechanical advance to cam/rotor shaft came from the factory with considerably more axial play than I would like to see. I have a trick that will get you to zero axial play in the mechanical advance to cam/rotor shaft portion and a perfect 0.005in axial play between the drive dog to distributor body.
Reject any with obvious damage, such as crushed or cracked aluminum bodies and rusty pitted breaker point cams.
Part 3: New Parts you will need
**Bosch and Beru were original equipment suppliers for VW ignition components. Wells vehicle electronics makes good quality replacements as well. Hard to go wrong with any of the above.**
-Distributor cap
-Rotor
-Engine oil
-Wheel bearing grease
-Points/cam grease (grease usually comes in a small capsule with the points)
-condenser
-M6 wavy spring washers
-2 x ~7/8in od fiber washers with a max id of 1/2in (can always drill out smaller holes to 1/2in). I prefer them to be a 1/16th inch thick, which is about double the thickness of the stock fiber washers. I'll explain why I want these thicker later. I got 3/8in*7/8in fiber washers from Menards and drilled out the center to 1/2in.
-possibly braided flexible cooper leads for grounding the breaker plates, solder, and wire cutters. Hint, look for desoldering wick or heavy braided leads from an old blown woofer from a large loudspeaker. Some old braided leads on the old distributors are frayed from flexing over many many cycles and should be replaced. Desoldering wick is less than a buck per foot. It's usually sold in five foot rolls. Check your local Radio Shack.
Part 4: Tools needed for a simple refresh job
-Flat head screw driver
-tweezers
-Calipers or thickness gauge
-Punch less than 4mm od and a hammer. I like plastic ended hammers. If you miss, you won't likely bugger up things that shouldn't be buggered up (think brittle cast aluminum bodies).
-Dental picks are very helpful, but not needed if you are skilled with a tweezers.
-Bench top vice as a third hand for holding things as you disassemble/reassemble
-dial indicator is a bonus, but not needed. With creativity a good calipers and feeler gauge set will get you were you need to be.
-Soldering iron if replacing the braided copper flex wire on the breaker plate. A 100w + soldering gun is preferred. A 30w soldering iron will work, but will take a long time. Don't even bother trying a 15w iron.
Disassembly
Start with the outside and work your way inwards. This step is pretty self explanatory. The pictures will show you the general order of how I go about things and offer some hints along the way.
Assemble Advance/Breaker Plate
Now that the advance/breaker plate is completely apart, clean it up, lube it, and reassemble it. Small hobby paint brushes work well for applying grease to small pieces.
Disassemble, Clean, and Assemble Mechanical Advance
With the advance/breaker plate assembly out of the way, move on to the next inner most component. The mechanical centrifugal advance has some, by now, rather old poly bushings. Go easy on them, especially the bushings that secure the springs to the base plate. The butterfly tabs on the top crack off very easy. Fortunately, all they must do is keep the springs from slipping off. If one of the butterfly wing tabs cracks off, just make a small blob of epoxy over the top. That will do the trick. Epoxy should not be used anywhere else inside the distributor.
Assemble Distributor
Time to assemble the distributor. Not hard, but there are a couple tricks I used to take up as much of the axial play in the rotor as I could. There are two spots responsible for end play.
The first is the washer and shim stacks sandwiched between the flyweight plate and body, and between the drive dog and body. Bosch used a pair of 0.8mm thick fiber washers, one on each side. You can buy these in kits that have washers and shims to set end play, or you can use the shims you have, get a pair of 7/8in od * 1/16in thick fiber washers, and sand them down to size. You can get very close to 0.005in of end play that way. I would keep a pair of shims between the drive dog and fiber washer. Sand that fiber washer down to 0.8mm. Then adjust end play by messing about with the shims and sanding down the washer inside the distributor. You should sand down the inner fiber washer until you have at least one shim inside. Two shims would be preferable. Stick a piece of 220 sand paper down to a flat surface and use a palm sander with 220 grit to sand down fiber washers. If you keep measuring the washer thickness every so often, you will be able to keep things nice and flat. If you notice one part of the washer is thinner than another, apply slightly more pressure to the opposit side for a few seconds, measure, and continue sanding as normal. It shouldn't be hard to keep everything level with in 0.01mm, or 0.02mm at the most.
The second area that often has a lot of play is the rotor/point cam shaft. It rides over a central fixed shaft e tending upwards from the flyweight plate. At the top there is an M6 flat washer and a round wire clip that holds the rotor/point cam shaft on. It is a rather crude way of keeping the shaft in place. What I did is remove the M6 flat washer and replace it with a pair of M6 wavy washers. That was just enough to take up the play without making things tight. Every distributor will be a little bit different. Maybe the flat washer and a wavy washer is enough, or maybe the flat washer alone is good. You may find you need to grind down the edges to get a good fit. Play around with it to find the combination that works right for you.
Replace Copper Point Ground Braid
This is an important step that many people overlook when cleaning up distributors. With age, the braided copper lead that bridges the two advance/breaker plates begins to fray at the ends. The flow of electricity from the top advance/breaker plate to the body can be impeded by the grease film between the top and bottom plate. Ignition coils usually have a primary resistance of 3-4ohms. With 12 volts, that will result in a minimum of 3amps of current draw that must pass from the top plate to the bottom plate that mounts to the body. With the alternator kicking out 14.4 volts, you could be approaching the 5amp mark with a 3ohm coil. Either way, that is a significant amount of current. The need for a solid ground bridging the two plates now be obvious.
Desoldering braid works great, and is what I prefer. Flex leads salvaged from medium or large loudspeaker drivers also work if that is what you happen to have laying around. Desoldering wire is cheap, and you can use it for other projects down the road. At less than a dollar per foot it would be silly not to go out and buy five feet of the stuff.
If you have never soldered before, you should note that solder will flow toward the heat source. Heat is your friend. Little 15w soldering irons are great for soldering printed circuit boards and fine wires, but they can't keep up when components are attached to a large heat sink like the advance/breaker plates. I would consider a 30w iron to be the absolute minimum. A soldering gun is the ideal tool for the job. To aid in heat transfer, tin the tip of the soldering gun/iron. This means melting a little drop of solder on it. Now, place tinned tip onto copper over the point you wish to attach the braid. Let it sit for a minute or so. You are trying to get the contact point and the copper hot enough so that they can melt the solder when you touch the solder to it. Don't feed solder onto the gun/iron itself. Solder flows towards the heat, remember? Feed solder onto contact point so it melts onto it and then flows through the copper braid towards the gun/iron. Once solder has wicked from the contact point up into the copper towards the gun/iron, lift off and let joint cool. It should be nice and solid. If you have to touch solder to the gun/iron to get it to melt, you are not using a tool with enough heat. Find a more powerful one so you can make a proper connection. I do all this with the points in place. That way I can be sure the new copper braid will not interfere with any parts inside the distributor.
Final Assembly: Cap, Rotor, etc.
This would be a good time to ensure things work smoothly. Use distributor point/cam grease on cam and rubbing block. It is sticky high temp stuff that is designed specifically for the application. Usually the points come with a small capsule of the grease when you buy them. Spin the drive dog with your fingers. It should turn freely. You should have already set end play at the drive dog end, but it isn't a bad idea to check again. Now grip the drive dog and the rotor/point cam shaft in either hand and twist them gently. It should twist a few degrees in one direction with some resistance. Let the rotor/point cam shaft go and it should quickly snap back. It should not be able to rotate any in the opposite direction. Now apply a vacuum to the vacuum can nipples. Vaccum to the larger inner nipple should retard the top advance/breaker plate a good amount. The smaller outer one should advance plate slightly. If everything feels good, button it up.
Off Road Trick: Keep Grit Out
For those who drive off road and are worried about grit entering the distributor body, you can attach a piece of breathable material over the four small vent holes on the underside of the distributor body. Jeff Hibbard recommends foam in his off road VW prep guid, but I prefer felt because it is easier to work with and gets the job done.
That is all that is to it. This is something that anyone at home can do with basic hand tools. It will be a great improvement for your old gummed up distributor. I know that I could certainly feel a substantial improvement. Both advance mechanisms should now operate much more smoothly from cleaning and lubing all of the parts, and you should notice a reduction in timing bounce as a result of tightening up the end play at the rotor. I hope you guys find this both useful and helpful!
Also, GoodVolks members, it you want some Desoldering braid, I have a couple feel laying around. Let me know if you want some. I will gladly cut a piece and send it to you.
In the 70's as emissions regulations were ramping up, more precise control of combustion temperatures and speeds were deemed nescesary. Various companies adopted various methods of reducing hydrocarbons. VWs response was the 34 PICT 3 or 4 on single carbed engines, 34 PDSIT 2 and 3 for dual carbed engines, and Bosch Djet/Ljet fuel injection. These systems targeted issues of slow combustion speeds and low combustion temperatures at idle, which inevitably resulted in imcompleat burning of the air/fuel. Earlier solex carburetors operated approximately stoichiometrically (~14.7:1 air/fuel) at idle. While this works great under load, the high vacuum at idle results in a significantly lower density air/fuel charge in the combustion chamber. This lower density charge burnd slow and a sizable portion of the gasses were exhausted out the tailpipe before they even had a chance to burn. The new generation of Solex carbs and Bosch fuel injection introduced the lean burn concept in 1970/71 which would eventually be adopted by all automakers come the end of the decade. The idea is that a leaner than stoichiometric charge of air/fuel (within reason) increases the oxidation rate of the fuel because each gasoline molecule is in close proximity to more oxygen, so the chemical reaction can happen faster. Immagine you are a molecule of gasoline and flies are oxygen. You are in a small room with fifteen flys. Catching them all is easy because the room is small and you are in close proximity to them (stoichiometric, dense air charge, low vacuum partial to full load). Now Immagine how much longer it would take you if you tried to catch those same fifteen flies in a large room (stoichiometric, lower charge density, high vacuum idle). So, if you wanted to catch fifteen flies in a large room in the same time it would take to catch fifteen in a small room, it would help to have more flys in the large room ( lean burn with more O2, low charge density, high vacuum idle). Sounds great, but the rapidly burning hot lean combustion will create peak pressure to early in the cycle with the standard 7.5deg before top dead center timing. To keep the system from fighting itself because of the rapid combustion, the timing needs to be retarded in order to keep maximum pressure in the cylinder partway down the power stroke. This is why you see the timing at idle for 34 PICT 3 and PICT 4 (California), 34 PDSIT 2/3, and all 71 and newer Bosch fuel injections set at either 5deg or 10deg AFTER top dead center.
These systems require a completely differant advance curve, which is why simple mechanical and earlier SVDA distributors refuse to play well with them. Engine problems that arise when using mechanical or SVDA distributors with lean burn systems depend on how the user times their engine. Time the engine for max advance at 28ish rpm, and the timing will be far to advanced at idle and the engine can sound and run like it is pinging, run very rough and hot, and may backfire through the carb because of the large amount of pressure that builds rapidly before the intake valve has a chance to close. Ok, so you loosen the clamp and twist the distributor around so it is timed properly at 5-10deg after top dead center at idle. Now you get nasty flat spots off idle and a gutless wonder up top because of a lack of total advance. A compromise between the two extremes helps little.
To my knowledge, nobody is making suitable replacement distributor for lean burn systems, so reusing the original Bosch distributors is the only option, and most here in the states are about 40 years old give or take a few, and could really use some love. Thus, the purpose of this article. Enjoy!
Part 2: What makes a good refresh candidate?
There are two basic sub assemblies inside the distributor that cause most of the problems. They are the vacuum advance/breaker plate assemble, and the mechanical advance assembly. There are other areas of interest, but those two failure points can make the difference between a salvageable distributor and a spare parts bin special.
Start with the vacuum mechanism. Suck on the nipples and see if the breaker plate moves. The nipple on the outer side should advance the breaker plate a small amount, and sucking on the larger inside nipple should retard the breaker plate a considerable amount. If this checks out, repeat the steps again, but hold the vacuum by covering the nipple with your tongue or pinching off the line if using a hose. With the vacuum held, the breaker plate should not move from its advance or retard position. If it slowly creeps back to neutral, you got a leaky diaphragm which is no good. Move on and try another one, or keep it if you want something to rob parts from in the future.
Next check to make sure the mechanical advance is not frozen up. Hold the drive dog on the base and twist on upper portion of the shaft where the rotor attaches. It should be able to rotate slightly with resistance in one direction only, and then it should snap back to its original position when released. If it is stuck, the previous owners (or you!) forgot to add a drop or two of oil to the felt wick underneath the rotor cap with every oil change, and the shaft seized onto the bushings. Although it can probably be separated, it is most likely toast anyways because the tolerance between the shaft and bushings of the mechanical advance mechanism are very precise, and any clean up work done would result in too much radial play of the rotor. Speaking of radial play, avoid distributors that have excessive radial play at the rotor end of the deal. Ideally this would Be less than a couple thousands of an inch, but these days you may have to settle for 5 thou or so. There are still a lot of good cores out there, so you shouldn't have to resort to machining and replacing bushings to get something acceptable. Don't worry about excessive axial play. The mechanical advance to cam/rotor shaft came from the factory with considerably more axial play than I would like to see. I have a trick that will get you to zero axial play in the mechanical advance to cam/rotor shaft portion and a perfect 0.005in axial play between the drive dog to distributor body.
Reject any with obvious damage, such as crushed or cracked aluminum bodies and rusty pitted breaker point cams.
Part 3: New Parts you will need
**Bosch and Beru were original equipment suppliers for VW ignition components. Wells vehicle electronics makes good quality replacements as well. Hard to go wrong with any of the above.**
-Distributor cap
-Rotor
-Engine oil
-Wheel bearing grease
-Points/cam grease (grease usually comes in a small capsule with the points)
-condenser
-M6 wavy spring washers
-2 x ~7/8in od fiber washers with a max id of 1/2in (can always drill out smaller holes to 1/2in). I prefer them to be a 1/16th inch thick, which is about double the thickness of the stock fiber washers. I'll explain why I want these thicker later. I got 3/8in*7/8in fiber washers from Menards and drilled out the center to 1/2in.
-possibly braided flexible cooper leads for grounding the breaker plates, solder, and wire cutters. Hint, look for desoldering wick or heavy braided leads from an old blown woofer from a large loudspeaker. Some old braided leads on the old distributors are frayed from flexing over many many cycles and should be replaced. Desoldering wick is less than a buck per foot. It's usually sold in five foot rolls. Check your local Radio Shack.
Part 4: Tools needed for a simple refresh job
-Flat head screw driver
-tweezers
-Calipers or thickness gauge
-Punch less than 4mm od and a hammer. I like plastic ended hammers. If you miss, you won't likely bugger up things that shouldn't be buggered up (think brittle cast aluminum bodies).
-Dental picks are very helpful, but not needed if you are skilled with a tweezers.
-Bench top vice as a third hand for holding things as you disassemble/reassemble
-dial indicator is a bonus, but not needed. With creativity a good calipers and feeler gauge set will get you were you need to be.
-Soldering iron if replacing the braided copper flex wire on the breaker plate. A 100w + soldering gun is preferred. A 30w soldering iron will work, but will take a long time. Don't even bother trying a 15w iron.
Disassembly
Start with the outside and work your way inwards. This step is pretty self explanatory. The pictures will show you the general order of how I go about things and offer some hints along the way.
Assemble Advance/Breaker Plate
Now that the advance/breaker plate is completely apart, clean it up, lube it, and reassemble it. Small hobby paint brushes work well for applying grease to small pieces.
Disassemble, Clean, and Assemble Mechanical Advance
With the advance/breaker plate assembly out of the way, move on to the next inner most component. The mechanical centrifugal advance has some, by now, rather old poly bushings. Go easy on them, especially the bushings that secure the springs to the base plate. The butterfly tabs on the top crack off very easy. Fortunately, all they must do is keep the springs from slipping off. If one of the butterfly wing tabs cracks off, just make a small blob of epoxy over the top. That will do the trick. Epoxy should not be used anywhere else inside the distributor.
Assemble Distributor
Time to assemble the distributor. Not hard, but there are a couple tricks I used to take up as much of the axial play in the rotor as I could. There are two spots responsible for end play.
The first is the washer and shim stacks sandwiched between the flyweight plate and body, and between the drive dog and body. Bosch used a pair of 0.8mm thick fiber washers, one on each side. You can buy these in kits that have washers and shims to set end play, or you can use the shims you have, get a pair of 7/8in od * 1/16in thick fiber washers, and sand them down to size. You can get very close to 0.005in of end play that way. I would keep a pair of shims between the drive dog and fiber washer. Sand that fiber washer down to 0.8mm. Then adjust end play by messing about with the shims and sanding down the washer inside the distributor. You should sand down the inner fiber washer until you have at least one shim inside. Two shims would be preferable. Stick a piece of 220 sand paper down to a flat surface and use a palm sander with 220 grit to sand down fiber washers. If you keep measuring the washer thickness every so often, you will be able to keep things nice and flat. If you notice one part of the washer is thinner than another, apply slightly more pressure to the opposit side for a few seconds, measure, and continue sanding as normal. It shouldn't be hard to keep everything level with in 0.01mm, or 0.02mm at the most.
The second area that often has a lot of play is the rotor/point cam shaft. It rides over a central fixed shaft e tending upwards from the flyweight plate. At the top there is an M6 flat washer and a round wire clip that holds the rotor/point cam shaft on. It is a rather crude way of keeping the shaft in place. What I did is remove the M6 flat washer and replace it with a pair of M6 wavy washers. That was just enough to take up the play without making things tight. Every distributor will be a little bit different. Maybe the flat washer and a wavy washer is enough, or maybe the flat washer alone is good. You may find you need to grind down the edges to get a good fit. Play around with it to find the combination that works right for you.
Replace Copper Point Ground Braid
This is an important step that many people overlook when cleaning up distributors. With age, the braided copper lead that bridges the two advance/breaker plates begins to fray at the ends. The flow of electricity from the top advance/breaker plate to the body can be impeded by the grease film between the top and bottom plate. Ignition coils usually have a primary resistance of 3-4ohms. With 12 volts, that will result in a minimum of 3amps of current draw that must pass from the top plate to the bottom plate that mounts to the body. With the alternator kicking out 14.4 volts, you could be approaching the 5amp mark with a 3ohm coil. Either way, that is a significant amount of current. The need for a solid ground bridging the two plates now be obvious.
Desoldering braid works great, and is what I prefer. Flex leads salvaged from medium or large loudspeaker drivers also work if that is what you happen to have laying around. Desoldering wire is cheap, and you can use it for other projects down the road. At less than a dollar per foot it would be silly not to go out and buy five feet of the stuff.
If you have never soldered before, you should note that solder will flow toward the heat source. Heat is your friend. Little 15w soldering irons are great for soldering printed circuit boards and fine wires, but they can't keep up when components are attached to a large heat sink like the advance/breaker plates. I would consider a 30w iron to be the absolute minimum. A soldering gun is the ideal tool for the job. To aid in heat transfer, tin the tip of the soldering gun/iron. This means melting a little drop of solder on it. Now, place tinned tip onto copper over the point you wish to attach the braid. Let it sit for a minute or so. You are trying to get the contact point and the copper hot enough so that they can melt the solder when you touch the solder to it. Don't feed solder onto the gun/iron itself. Solder flows towards the heat, remember? Feed solder onto contact point so it melts onto it and then flows through the copper braid towards the gun/iron. Once solder has wicked from the contact point up into the copper towards the gun/iron, lift off and let joint cool. It should be nice and solid. If you have to touch solder to the gun/iron to get it to melt, you are not using a tool with enough heat. Find a more powerful one so you can make a proper connection. I do all this with the points in place. That way I can be sure the new copper braid will not interfere with any parts inside the distributor.
Final Assembly: Cap, Rotor, etc.
This would be a good time to ensure things work smoothly. Use distributor point/cam grease on cam and rubbing block. It is sticky high temp stuff that is designed specifically for the application. Usually the points come with a small capsule of the grease when you buy them. Spin the drive dog with your fingers. It should turn freely. You should have already set end play at the drive dog end, but it isn't a bad idea to check again. Now grip the drive dog and the rotor/point cam shaft in either hand and twist them gently. It should twist a few degrees in one direction with some resistance. Let the rotor/point cam shaft go and it should quickly snap back. It should not be able to rotate any in the opposite direction. Now apply a vacuum to the vacuum can nipples. Vaccum to the larger inner nipple should retard the top advance/breaker plate a good amount. The smaller outer one should advance plate slightly. If everything feels good, button it up.
Off Road Trick: Keep Grit Out
For those who drive off road and are worried about grit entering the distributor body, you can attach a piece of breathable material over the four small vent holes on the underside of the distributor body. Jeff Hibbard recommends foam in his off road VW prep guid, but I prefer felt because it is easier to work with and gets the job done.
That is all that is to it. This is something that anyone at home can do with basic hand tools. It will be a great improvement for your old gummed up distributor. I know that I could certainly feel a substantial improvement. Both advance mechanisms should now operate much more smoothly from cleaning and lubing all of the parts, and you should notice a reduction in timing bounce as a result of tightening up the end play at the rotor. I hope you guys find this both useful and helpful!
Also, GoodVolks members, it you want some Desoldering braid, I have a couple feel laying around. Let me know if you want some. I will gladly cut a piece and send it to you.
