VW/Toyota Distributors (With My Notes)

How does the advance curve work out for the VW? I'm assuming it must be OK or the main man (respectfully) would have mentioned something about modifying it.

JohnF

First off, it's not a bolt-up. You have to do quite a bit of machining on the >Toyota distributor. That means you need access to a lathe and know how to use >it. >So why did I call it a fairly simple modification? Because it is, if you >happen to be a machinist and understand a few basic principles of both machine >work and engines, one of which is the fact that, at least in theory, the >distributor from ANY four-cylinder Otto cycle engine can be used on any other >four-cylinder Otto cycle engine. In theory. That's because the cam, reluctor, >electronic switch or whatever has four poles. Trying to use a distributor from >a six or eight cylinder engine would increase the complexity of the task by >several orders of magnitude, making it so difficult you'd probably be better >off to start from scratch. But if you have a distributor from a four cylinder >engine you're already about 90% of the way to your goal.

scientist to understand that it's pretty simple to SHORTEN a shaft that's a bit

too long... you just cut the thing off, whereas trying to LENGTHEN a shaft can >be blindingly difficult. By the same token, if you have a bar of metal 2" in >diameter it's a simple chore to turn it down to some SMALLER size... but >virtually impossible, within practical limits, to turn it into a size LARGER >than 2". This also applies to holes. If you already have a hole, making the >hole LARGER is a trivial task whereas making it SMALLER is extremely >difficult... you would have to weld it up and remachine, being careful to >preserve your center. >So how does all of that apply to the modification of a Nippondenso distributor? > First off, the spigot shaft of the Toyota distributor is EXACTLY the same >diameter as the spigot shaft of a Bosch distributor - the thing will plug into >the hole in the Type I crankcase without any machining. It won't FIT but only >because the Toyota distributor's spigot shaft is TOO LONG. But as I pointed >out above, shortening things is pretty easy. Finally, the Nippondenso >distributor has a LOT of extra metal in its base. You can machine away nearly >a quarter of an inch off the Toyota distributor without weaken it, plus you can >saw off the clamping lug and a couple of casting bosses, allowing you to use >the standard VW distributor clamp. (Which is a rather shoddy piece of goods >but it saves you having to figure out a better method of clamping.) >The distributor's shaft is too long but it's almost exactly the same diameter >as the Bosch distributor shaft -- you simply cut the thing to the proper length >and drill it to accept the dog gear from the VW distributor. Along the way, >you will have to move the lower bearing in the Nippondenso distriubutor but >here again, the machine work is relatively easy - you simply deepen the >existing bore. >So why would you want to do all that? Because a new (or nearly so) Nippondenso >composite distributor is about a hundred times better than what you're probably >running in your VW right now. >Like all modern vehicles the Toyota used a composite distributor, having vacuum >sensing to provide the necessary sensitivity, combined with a centrifugal >advance mechanism to provide a wide dynamic range. This is a completely sealed >distributor, with an O-ring between the body and the distributor cap, which is >installed with screws rather than spring-type clips. Best of all, it comes >complete with a modern electronic ignition system. >Inside the Nippondenso distributor is a magnetic pick-up coil. Instead of a >cam on the distributor shaft operating a set of ignition points, it has a >four-lobed reluctor. Each time a lobe of the reluctor sweeps past the magnetic >pick-up it induces a voltage in the pick-up unit. That voltage goes to a solid >state 'ignitor' - a tiny amplifier and a husky transistorized switch -- >attached to the ignition coil. The 'ignitor' is connected to 12v and ground >and controls the discharge of the coil, just like on a modern car :-) >So why isn't everyone using Toyota distributors? Well... quite a few guys are. > But the distributor is physically larger than the Bosch and can't be used with >some mechanical fuel pumps. On the other hand, the later model Toyota's use an >HEI system -- the coil, pick-up and ignitor is all built into the cap of the >distributor. Once you get it set up it's a virtually bullet proof system that >can win you the race. For your daily driver, it's a zero-maintenance ignition >system, other than checking the air-gap every 50,000 or so... about the same >time you need to replace the plugs, if you're running platinums. >If your stock Bosch unit is still within spec there's no reason to replace it. >But if your shaft is showing some wobble you might want to look into the mod. > As for Toyota (or Nippondenso) part numbers, there's a bunch of them, just as >there are for the different Bosch distributors. The one I've modified came off >a 22R carburetted engine and the data plate reads '19100-35130,' which I think >is the Nippondenso part number, followed by '29100-8801,' which I think is the >Toyota p/n. But I don't really know (or care). In the process of fooling >around with this mod I've accumulated several Nippondenso distributor (at about >$20 each). The castings are identical but the numbers are different. That >also applies to the ignitor & ignition coil, of which I've used two. Both >worked exactly the same (same connections, etc) and while physically identical, >they had different part numbers. >Finally, I've no idea how well the thing will hold up. In the Toyota the >driven-end of the distributor shaft is supported by a bushing. When modified, >the driven end is free (ie, as with the Bosch unit). I suspect the lack of >support will lead to accelerated wear of the shaft bearings but I've no idea >how long it will take for the thing to fall out of spec. One thing I do know, >it's a hell of a lot easier (and less expensive) to find a good-condition >Nippondenso distributor than it is to find a VW distributor that's still within >spec.

Aftermarket VW distributors such as the Mallory do exist for VW's.

My inclination was always to transplant a Mopar Hall-effect reluctor, pickup and control box onto the extant Bosch mechanicals. I am extremely fond of Mopar electronic ignitions, mostly because once you get past the potting-early ones are dissolvable wax-they are user-repairable. You can shotgun all the parts for $10 out of the Digi-Key catalog, even if you have no electronic skills whatsoever.

Reply to
Bret Ludwig
Loading thread data ...

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.