Sparkin' on the Cheap

Flying isn’t that hard. Birds fly. So do fish. Even insects. But if you wanna enjoy the thrill of powered flight you’ll probably need an engine and if it gets its power from burning gasoline then you gotta figger out some way to light the fire. Always been something of a problem, lighting the fire. Back during our Civil War they used what they called a ‘glow tube’ to light the fire. Closed brass or silver tube, closed end inside the combustion chamber, open out outside being heated by a kerosene or acetylene lamp. Actually worked, too. Engine put out nearly half a horsepower at about 100rpm and only weighed about 700 pounds.

State of the art, 1865.

Of course, soon as they had an engine, some kid wanted to make himself a motorsickle. Or mebbe a hot-rod.

Didn’t work too good. Soon as the thing started to move it would usually blow out the kerosene lamp, glow tube would cool off, engine would crap out. Ignition failure. Civil War motorcycle gang, Nazi helmets, Originals stiff as a board, lined up there on the side of the road... Hell of a problem.

Some guys used spark ignition. Low voltage, make & break stuff. But that meant a buncha batteries and they weren’t all that good back before we had the Energizer Bunny. Or they could generate their own lektrcity. Mike Whats-his-name... Faraday... had figgered out how to generate lektricity about thirty years before. All you had to do was twirly a coil of wire between the poles of a magnet and lektricity would magically appear in the coil. Unfortunately Civil War magnets weren’t any better than Civil War batteries. Just soft iron bars. Oh, you could magnetize the things but not very much nor for very long. If you wanted to produce the same amount of current you’d get from your bank of batteries you needed some humungous magnets, size of a wagon wheel. Magnets that big, your lektricity-maker ended up weighing about the same as the batteries, not only because you needed a lot of big soft iron magnets but because your coil was kinda fat. Big wire. And the insulation was just string or varnished thread wrapped around the wires, which pushed the wires pretty far apart so you needed a BIG coil to get any juice. And slip-rings, since you had to get the juice out of the coil once you made it.

Folks called it a ‘magneto’ because of the magnets, I guess. First ones weighed about a hundred pounds. But it actually worked and you ended up with an engine that was handier than steam because you didn’t ned a firebox and a boiler. Not a real handy engine, of course. Heavy as hell. Didn’t put out a lot of power and only ran at one speed. But the fire was all inside and there wasn’t any boiler to explode and you could run the thing yourself; didn’t need a certified Engineer.

Wasn’t a Hog of course but the thing did go. Bad as it was, it sold like hot-cakes since it cost less than a small steam-powered engine. And because it sold like hot-cakes a lot of people were building them. And improving them, too.

Twenty years goes by. Engines got smaller and more powerful. So did the magneto, thanks mostly to Elisha Gray, who developed a geared magneto that could produce nearly forty volts, thanks to stronger magnets, smaller wire, better insulation and those gears. That made the thing small enough to fit inside his telephones. Spin the crank, it could generate enough juice to trip the indicator down at Central, tell the operator you were on the line. Couldn’t use light bulbs because Edison hadn’t finished stealing the idea from Swan just yet but the solenoid-actuated ringdown indicator worked pretty good, assuming you weren’t too far from Central and the iron wire running along the fence posts wasn’t too rusty.

Better magneto made for a better engine but most real engines, like the ones in the trucks that could now be found all over Europe, still used glow tubes. Which sat the truck on fire now & then but glow tubes were more reliable than that silly Mag-Neat-Oh or that Make & Break method of generating the spark, rubbing the piston against the Sparking Rod inside the combustion chamber.

Stationary internal combustion engines had come even farther. Now that most towns had electric lighting they used a door bell arrangement to generate an alternating current that could be stepped-up by a transformer and fed to a spark plug, just as soon as they invented spark plugs. Didn’t work for those trucks, though. The vibrating reed-relay that buzzed those coils up to as much as five thousand volts was a real power hog and ran down your dry cells quick like a bunny.

Which is why the Wright brothers used Make & Break to light their fire. No spark plugs. Friction-drive magneto pressed into service as a dynamo, powered by putting a little wheel on the input shaft and letting it rub against the flywheel - - gave them about ten volts. Sparking bar inside the combustion chamber. Tried & true ignition system, having been in use for nearly fifty years by the time the Wright brothers flew. They’d heard about a new-fangled high-voltage magneto developed by a German outfit. Put out enough voltages to jump the gap on a spark plug, assuming you had spark plugs, which the Wright’s didn’t. Not at first.

Robert Bosch got into the magneto game in 1887 and made a pretty good magneto, although not very many of them. By 1896 he’d only sold a thousand of the things but he kept plowing the money back into the business, improving his product. Because everyone understood that if you wanted to make a hot-rod or a motorcycle you couldn’t afford the half-ton weight of the typical gasoline engine. Trucks, okay. But not motorcycles or flying machines or a Z-car. For that you needed a light engine. But it had to be a powerful light engine and all else being equal, that meant it would have to spin at a fantastic rate of speed, probably more than A THOUSAND REVOLUTIONS PER MINUTE, which was a lot faster than any engine was running at that time. Try running a Make&Break ignition at a thousand rpm, it’d break off the Sparking Rod or the insulated seal around the Sparking Rod gland-nut would leak even more than it already did and steal all your power. Carl Benz, a friend of Bob’s and another early car nut, referred to the ignition puzzle as “...the problem of all problems.” He said that in 1880 and odds are, he was still saying it in 1896. Nope. Couldn’t do it.

Actually, you could do it... if you used a sparking Plug with a fixed gap instead of Make & Break with its moveable Spark Rod with its variable gap. In fact, they’d already done it with stationary engines. But to jump the gap on a sparking Plug you needed thousands of volts, not just tens of volts. And while you could make that kind of voltage by plugging your ignition system into the wall, or powering a vibrator with a bank of batteries, nobody knew how to do that with a magneto.

Except for a guy named Gottlob Honold, who worked for Bob Bosch. And even Gottlob wasn’t sure he could do it, he just had this idea about how, maybe, it could be done, based on a couple of principles about inductance that Mike Faraday laid down fifty years before and some of the tricks Elisha Gray had come up with. Gottlob was lucky enough to be working for Bob, winding coils for those thousand pretty-good magnetos. Bosch who told him, Sure, take your best shot at it. Which Gottlob did, solving one problem after another over a span of five years or so until December of 1901 rolled around and he showed his boss a working model of a reliable, dependable magneto that put out enough juice to be used with a spark plug. “You really have hit the bulls-eye!” said Bosch. (But in German, of course.) By 1906 Bosch magnetos was bringing in over a million dollars a year, thanks to Gottlob Honold, who was given a raise and allowed to take Saturdays off.

What Gottlob had done was to put a transformer inside the magneto and to apply a couple of known but heretofore undeveloped electrical theories to make the transformer kick out a hot, blue-white spark exactly when needed, using an electrical switch driven by the magneto. Once the spark was generated it was connected to the proper spark plug via a rotary switch that was also driven by the magneto. The first switch, which controls the flow of juice to the primary side of the transformer, is what we today call the ‘points’ while the second switch, the one that directs the output of the secondary winding to the spark plug, is called the rotor and distributor cap.

Starting to sound familiar? Well, it should. Because the principle of spark ignition has remained pretty much the same right up to this day, despite something better having come along in the 1960's.

As soon as the Bosch high-tension magneto hit the market everyone started copying it. Or trying to improve on it. Like a young guy named Charles Franklin Kettering who worked for the National Cash Register Company in Dayton, Ohio. Which just happens to be where the Wright’s hailed from. In a sense, Dayton was the Silicon Valley of its day.

Magnetos were nice. Nice and expensive. Each was virtually hand-made. Their superb quality ensured their reliability but it also guaranteed the need for a high level of skill to maintain and repair them. They were a complete generating set and ignition system compressed in a tidy little package. And if any single part of that tidy little package went bad, the thing wouldn’t work and finding someone who knew how to fix it was roughly the same as for finding fur on a turtle.

But magnetos weren’t perfect. Since the amount of juice provided by the permanent magnet dynamo was proportional to the rotating speed of the coil, they were a bitch to hand-start. Once you got the buggy running things were okay. The faster it ran, the better the spark, up to the point where the electrical insulation began to break down. Hand-cranked on a cold morning? Forget it. Ford’s buzz-box ‘ignitors’ were the hands-down winner when it came to crank-starts because when you got right down to it, your horseless carriage was pretty much of a joke if you couldn’t start the thing. And for a lot of folks, crank-starting a car was about like programming their VCR.

Chuck Kettering thought about the problem for a while then decided to take the magneto apart. Instead of that niffty little permanent magnet dynamo to provide the juice he decided to run the thing off a big lead-acid car battery. To keep the battery charged you’d have to fit the engine with some kind of electrical generator but now that Edison had copied the light bulb folks were even using them on cars, not only to replace the blindingly expensive acetylene-powered driving lights but even for that new fad of having a light come on when you stepped on the brake. (Cute. But it’ll never catch on.) And besides, Chuck had a crazy idea about replacing the hand-crank with an electrically powered starter-motor, for which you’d need big battery... and some means of recharging it.

After tearing the magneto apart and spreading it around the table Chuck saw how you could retain the transformer principle that gave you such a nice hot spark while eliminating most of the complexity that made magnetos so expensive. Instead of building the transformer inside the magneto Chuck Kettering wound a new transformer, one you could bolt anywhere you wanted it. He put the points in a device driven off the engine’s cam. The points went into the bottom part of the thing. The top part was reserved for the task of distributing high voltage from the coil to the individual spark plugs, which everyone started calling the ‘distributor’ about ten seconds after Chuck invented the damn thing.

Now you had all the pieces of an effective spark-ignition system spread out where you could get at them. The components were larger and designed for mass production; no brains required. If a part of the system went bad, any damn fool, meaning you, could simply replaced that particular part and drive on. What you ended up with was a cheap, easily manufactured ignition system that was inexpensive, reasonably reliable, didn’t cost very much and took virtually no skill at all to maintain. And it was cheap. Best of all, it actually worked. (Did I mention it was cheap? Cuz it was, compared to a magneto.)

Genius or not, Charles Kettering hadn’t improved on the magneto in the electrical sense. Indeed, at high speed the Kettering ignition system doesn’t work nearly so well as a magneto. But boy did it make an engine easy to start! And it was cheap, too.

Auto makers loved it. At least, most of them. Ford stuck to his own patents. A fellow named Sloan, maker of a car he called the ‘Cadillac,’ took one look at Charles Kettering’s ignition system and said, “I take a million of them, please.” (Or words to that effect :-)

Which isn’t to say magnetos vanished. Far from it. But over the years the Kettering-type ignition system got better an’ better while magnetos stayed pretty much the same.

First big improvement was getting rid of that distributor with its rotor and graphite button and all them sparks as the thing whirled around. Just a year after Boss Kettering patented his ignition system a feller in England started using it on a two-cylinder motorsickle. What he did was to wind the coil with a center ground so that both ends of the secondary were hot. Snap the points, which you could now mount just about anywhere, and you got two sparks, one from each end of the winding. He wired the sparks to his two cylinders and roared off to win the Isle of Man.

Waaait a minute. Howz that gonna work, both cylinders firing at the SAME time. But the feller just smiled and roared off. From that day to this no one has been able to figure out how a Waste Spark ignition system works, largely because Auto Shop 101 doesn’t do a very good job of teaching how real engines work. But I’ll give you a hint: It doesn’t really matter what the other cylinder is doing when the spark fires. So long as that jug is near TDC on the compression cycle, then the engine will run... because if that jug is near TDC it means its twin is near TDC on the exhaust cycle, because that’s how Otto Cycle engines operate. The Good News is that you got to toss that damn distributor in the trash. You still had a set of points... somewhere. But they didn’t cause nearly so much trouble as that wonky distributor cap and rotor and having the ignition leads running all over the place.

That was in 1920, by the way.

In 1960 I built my first electronic ignition system and I wasn’t the first guy to do so (I hold a General Class ham radio ticket; hams are always fooling with stuff like that). Later on I built a capacitance-discharge ignition system. And a little while after that I built an ignition system that runs off a dilithium crystal, which worked great except those damn crystals became rare as hen’s teeth after they canceled ‘Star Trek.’

Nowadays they’re working on a spark plug that contains its own coil which also happens to be a fuel injector. But that can’t be right, according to Auto Shop 101 :-) It's also possible for someone building their own airplane to put together an ignition system that is more durable and more reliable than the traditional magneto. Wanna know how? Just stay tuned.

-R.S.Hoover

Crank Basics - I

When you build an engine from scratch you must round-up all the ancillary parts. In a previous article describing how to prepare the crankcase I’ve mentioned various kits of parts meant to ease this task. Unfortunately, such kits may not be as convenient as they appear.

The same situation applies to your crankshaft in that it requires a number of additional parts to make it usable. Here again, retailers offer kits but the odds are you’ll run into the same problems as with case-kits or hardware-kits.

A typical crankshaft kit contains a pair of Woodruff keys, the cam gear, spacer, distributor scroll gear, distributor pinion gear, two end-play shims, the oil slinger and a snap-ring. Typical price (April 2007) is about $50. Unfortunately, the kit is not complete, lacking a very critical spring. And it may not be complete with regard to your specific crankcase. Nor do they mention that some of the parts in the kit are liable to be used. (Note the wear marks on that pinion gear!)



The biggest potential problem is that such kits are liable to contain a cam gear from a 36hp engine. Such mix-ups don’t happen very often but like a mid-air collision, once is enough. (The two gears on the left are okay; the one on the right is for the earlier engine.)









Here is a kit of guaranteed-used parts I salvaged from junked engines at the cost of tearing them down. (Note the 'unimportant' little spring... that plays a critical role in reducing wear.)






The salvaged pinion (on the right) not only has less wear than the pinion from the after-market kit, I've treated it with a baked-on, dry film lubricant (Tech-Line Coatings DFL-1).






After failing to include the required spring I suppose it’s no surprise to see the notorious Racer Spacer included in such kits. The stock spacer ring has been known to fail on the drag-strip and on engines that regularly turn above 5000rpm. That makes the ten dollar Racer Spacer an absolute necessity... according to the ‘experts’ :-)

In fact, the stock spacer works perfectly well on flying Volkswagens, costs about six-bits and weighs less than the Racer Spacer.


External snap-ring pliers are one of the tools you'll need to assemble and disassemble the crankshaft. The jack-knife gives you some idea as to their size.






The jaws should look like this. Get a good pair. If they let the snap-ring slip it can bugger the #4 bearing journal. (The pair shown are Craftsman [brand name], about 30 years old. They've done a few engines :-)






You're also going to need an hydraulic press with a press-plate to match the cam gear, or a VW-specific gear-puller as shown below. Do not try to use a regular gear-puller for this task. You'll simply bugger the teeth of the cam gear, a very common problem on amateur-built engines. VW gear pullers are commonly available but they don't come cheap.





This one is kinda tatty-looking. I've had it for a while; had to repair it once or twice. Still works okay but I generally use an hydraulic press.






If you have access to a lathe and welding equipment you can make your own VW-gear puller for much less than the cost of buying one. The critical dimension here is the lip that supports the gear-teeth.



And along about here someone always says, "I won't need this becuz I'm only assembling the engine."

Dead wrong.

One of the most critical parts of engine assembly is balancing all of the rotating components. In the case of the crankshaft, it must be balanced in its fully assembled state (less any reciprocating components, such as the connecting rods). That means everything that attaches to the crankshaft and which rotates on the same axis must be installed at the time the assemblage is balanced. Everything... Gears, prop-hub, magneto drive, coaxial dynamo or what-ever. (Just another of those 'unimportant' little details :-)

(See the picture? The complete crankshaft assembly, from fan-pulley to flywheel, is being dynamically balanced.)


Then you take it all apart again for cleaning, installation of the #3 bearing and so forth. So you do need the gear-puller... if you want to build a good engine.

-R.S.Hoover

OIL PLUGS

“How do I remove the slotted plugs (screws?) in the oil control valves?”


Heat the case to about 200F and unscrew the things with a suitable screwdriver. If it’s an early case the slots are concave. Brazilian made stuff uses a shallower flat groove.

The screwdriver was a VW-specific item. Most American VW mechanics made their own, as I did. But the tricky bit was how to hold the crankcase whilst unscrewing the plugs. One method that works is to bolt that case-half to the top of the work-bench... assuming you’ve drilled a suitable pattern of holes to accept the studs :-) Another is to secure that half of the crankcase to a milling fixture designed to accept it, which should be available in any shop that does much VW work since the same fixture is used when opening up the cylinder bores for larger jugs.

If you have a MIG welder, a common method of removing stubbornly threaded plugs, broken studs and so forth is to weld a nut to the thing. Polishing the surfaces bright, establish a good ground, lay the nut (a large one is best) onto the slotted oil plug and weld the inside of the nut to the plug. This also heats the crankcase in that area and the plug can usually be unscrewed with only a moderate amount of torque. In fact, if you’re planning to use the engine in an airplane you’ll want some means of safety-wiring the plug. A drilled nut, welded to the plug, works quite well, although it’s a bit heavy.

HELP? (More on Plugs)

Help? About a dozen people asked that as they tackled the 1/2"-NPT thread for the bushing that accepts the oil temperature sensor. Relax; it’s no big deal. Clean things up then just follow me through.

National Pipe Thread or NPT has a taper of 3/4" to the foot. To cut a smooth NPT thread you begin with a hole that is big enough and has the right taper.

Root-diameter of the hole has to be at least .77". Since 1/2-NPT only has about half an inch of thread, the bottom of the hole has to about .015" smaller than the top or .77-.015 = .755... which is pretty close to 3/4" so start with that. Then open it up with a 47/64" for a depth of about a quarter of an inch and try your tap.

No guarantees for the above. I usually start with an 11/16" hole then use a 1/2-NPT reamer. The point here is that tapping the hole is no big deal if you start with a hole of the right size. (CAUTION: Too big a hole and you’ve screwed the pooch.)

HEADS & OIL

Several people expressed surprise that oil for both heads gets there via a single 5mm drilling... which can be partially blocked if the wrong aluminum plug is installed. Here’s a picture of that particular plug, now replaced with a 1/16-NPT pipe plug. But don’t take my word for it; go see for yourself. A fiber optic light-wand or even a length of safety wire as probe will allow the engine to explain things to you.







BLOCKED COOLER

Yes John, you can plug the cooler ports, as shown in the pix. The oil cooler is then installed downstream from the oil filter. No, I’m not saying you have to do it that way, I’m simply saying that’s the way I do it; you may build your engine anyway you damn well please. Thank you for sharing your opinion. You may be sure I’ll give it all the attention it deserves.

On ‘71 & later engines you’ll need a 1/4-NPT for the outlet port (ie, the one nearest the flywheel). 1/8-NPT works okay on the inlet, for both old & new crankcases.

OIL PRESSURE

Some years ago I had the line to the oil pressure gauge break on me. It was only an eighth-inch line but it didn’t have a metering orifice installed at the engine nor was it fitted with a shut-off valve. Lotsa fun :-)

Since then I’ve used an electronic oil pressure gauge whenever I can. Unfortunately, the transducer is fairly massive, plus it completes its circuit through the crankcase, meaning you gotta twist it tight. Mounted in the original location, jutting out to the side, it tends to work itself loose, resulting in an oil leak and erratic OP readings. So I’ve taken to mounting it vertically, with a diagonal stay between the body of the transducer and the existing oil cooler pad. But I still use the stock OP port. That’s where I connect the garden sprayer I use as a pre-luber, before firing up the engine.

CAM-FOLLOWER GALLERIES

On the front of the engine (Front means FRONT on Volkswagens) you can see where I’ve installed 1/16-NPT pipe plugs in the oil galleries serving the cam followers.

On the main oil gallery be careful not to install the plug too deeply as it butts up against the drilling that carries oil to the #1 cam bearing. And to the oil pressure control valve. That’s the two plugs underneath the main oil gallery. The upper one is the drilling for the pop-off port, which dumps excess oil into the crankcase at the outboard end of the cam-follower for the exhaust valve on #3 cylinder. The lower plug seals the drilling that allows leakage past the control valve’s piston to escape into the sump.

FULL-FLOW OIL FILTRATION

On the pulley-end of the crankcase you can see where I’ve threaded a 3/8-NPT to AN8 hose fitting into inlet to the oil cooler gallery. This is immediately adjacent to the port to the oil volume control valve, which on racing engines is usually opened up and replaced with steel seat for a ball-valve, doing away with the usual piston. The oil volume control valve port is 6mm in diameter. When you plug the oil cooler ports it’s customary to open up this port to 1/4" or even 5/16" to ensure adequate cold-oil flow. Also note the 1/16-NPT for the #4 main bearing. This drilling intersects with the drilling for the #3 main bearing and when plugged, forms a blind corner that likes to trap swarf. The upper-most plug is 1/4-NPT and marks another blind corner.

-R.S.Hoover

Who the hell are you?

(Someone asked.)

That's me. Taken at the keyboard by my $5 web-cam as I search GIMP-2 for the Beautify key.

Actually, I'm probably answering mail, a never-ending chore. But someone else noticed the picture of me leaning on the Arctic Circle was taken in 1996 and wondered if I was still alive :-)

HVX MODS

The air-cooled Volkswagen engine doesn’t have a very good lubrication system. (Which isn’t surprising, seeing as the design dates back to Xavier Reimspiess’ original 1931 ‘boxer’ engine.) Its inadequacies became evident in the late 1950's when me and a few other fools started hot-rodding the things.

The Ford Motor Company had recently published a study of the effects of oil filtration systems on engine wear and the results were so impressive that by the time you could say ‘Jack Robinson’ we’d retro-fitted our bugs with oil filters. But the main problem wasn't dirty oil but not enough oil, especially at high rpm. The inadequate amount of lubrication reaching the heads resulted in excessive friction, leading to high temps and failed valve-train components, which put you out of the race.

Auditing the engine’s lubrication system we found that all of the oil for both heads came through a single 5mm drilling. In theory, a hole that size should have provided more than enough oil. And it did, but only for the left-hand head. And then, only at low rpm. Which was fine for a stock 1200cc 36hp engine, but we’d already bored & stroked that puppy to nearly 1700cc and were running them at over 5000 rpm. But not for very long.

Volkswagen was aware of the valve-train lubrication problems and added a drilled oil channel to the rocker arms and a larger main oil gallery on later engines but the basic problem was that not enough oil was reaching the heads, especially the one on the right-hand side of the engine.

(NOTE: VW orientation is always relative to the driver. The right-hand head is the 1 & 2 cylinder bank, left-hand is the 4 & 3 bank.)

To get oil to the right-hand head, VW cuts a square groove in the bearing saddle for the #2 cam bearing. All of the oil to the right-hand side of the engine gets there through that channel. (And still does, if you haven’t modified the crankcase.)

To make matters worse, the oil to the heads gets there via the cam-followers... but only when that particular valve is actuated. In effect, the VW cam-followers act as a valve, shutting off the oil to the heads for approximately 92% of the time.



To get an engine that could run flat-out for 24 hours we had to get more oil to the heads. To do that we tried opening up the oil channel in the cam-bearing web. That worked but we still weren’t getting enough juice. So we modified the cam-followers to allow oil to reach the heads 100% of the time instead of only when the valve was actuated. Major improvement, but we were still seeing galling on the right-hand rocker-arm shaft, plus an occasional hair-pin fracture. What we needed was still more oil... especially to the right-hand side of the engine.





To do that, on the right-hand case half we extended the oil gallery for the cam-followers to intersect with a new oil channel we drilled into the #3 cam bearing web. Big, BIG change. And lower head-temps, too.

With that as a clue, we grooved the rocker-arm shafts to match the oil channels drilled into the rockers. Fitted with the Ford/Subie type swivel-foot adjusters, which have a matching oil channel, we could now provide the heads with approximately eight times as much oil as before. Heads ran much cooler... which meant the oil coming from the heads was hotter, so we had to come up with a better oil-cooling scheme. Which we did, moving the oil cooler outside of the blower housing.


All of which is pretty old news to anyone hanging out at the finish line. But a total blank to just about everyone else. The magazines were only interested in the mods when there was something to sell, such as an oil filter bracket or an oil cooler core. All of the fiddley bits that made the system work, such as drilling the new oil channels or grooving the rocker shafts, were seen as just more of those ‘unimportant’ details professional engine-builders are always messing with. (Most magazine 'technical' articles are nothing more than infomercials, intended to sell whatever product is being touted. )

A key point here is that a high-output engine needs all of the modifications described above: 100% filtered oil, increased oil volume to the right-hand side of the crankcase, 100% oil flow through the lifters, grooved rockers & rocker-arm shafts, and the Ford/Subie-type swivel-foot adjusters, which act as spray-bars. Some guys would modify the rockers and say they didn’t see any improvement. Others would modify the lifters and say the same. But not one in a thousand incorporated all of the modifications. And still don’t. But it’s interesting to note that Volkswagen included all of the modifications to the Type IV engine. In fact, you can find them in every modern-day engine. Which is just another of those ‘unimportant’ details.

-R.S.Hoover

AV -- PULLING THE PLUG II

Back in the Day, send a VW crankcase to Jack Riddle’s shop (aka Riddle Machine Company or ‘RIMCO’) for an align-bore or other machine work and it would come back with the some of the gallery plugs pulled & threaded for pipe-plugs, which were included with the returned case.

Why? According to Jack, machining caused swarf to get into the oil galleries and it was impossible to clean them out unless you pulled the plugs.

Which sounds perfectly logical, especially to any experienced mechanic or automotive machinist because seeing oil galleries sealed with pipe plugs is a familiar sight to anyone who has worked on aircraft engines or big V8's. And removing those plugs is a normal procedure in order to clean the oil galleries during overhaul. So pulling the plugs becomes a standard part of building a high-performance engine based on VW after-market components. Your engines run sweet, your customers are happy and those mysterious bearing failures become a thing of the past.

Not so with the shade-tree types, for whom pulling the plugs is another of those ‘unimportant’ details. Lotsa folks still don’t pull the plugs, especially on a new crankcase. Their logic goes something like this: New crankcase has never had any oil in the galleries so there’s nothing for the swarf to cling to; that a blast of compressed air is enough to clean everything up. And about here it might be a good idea to go read...

http://bobhooversblog.blogspot.com/2006/12/vw-pulling-plug.html

Starting about 1997 professional engine-builders here in southern California began seeing Brazilian crankcases in which the oil gallery for the #4 main bearing was blocked by the factory-installed plug. Which wasn’t a problem because we routinely pulled the plugs... which was how the problem came to light. Nor was it much of a problem to the dune-buggy crowd, folks who routinely did not pull the plugs. After all, the #4 main wasn’t a real main bearing - - it was added when VW found the asymmetric load of the blower caused the pulley to oval-out the nose of the crankcase. In most cases the blockage wasn’t 100% and the #4 usually got enough oil for passenger-car service. But complaints were heard now & then from the dune-buggy set who came up with an Idiot-Fix: running a 7/32" drill down the oil gallery for #4. Sometimes it even worked :-)

But it was a problem for flying Volkswagens, especially those who put the prop on the wrong end of the engine, which back then was virtually everyone. Here’s what Steve Bennett has to say about the problem...

http://www.greatplainsas.com/service1.html

Read both of the above articles and you’ll note significant differences in our methods; Steve drills-out the offending plug whereas I pull it out - - along with three others of that size. Steve threads the bore to accept a 1/8-NPT socket-head pipe-plug whereas I used whatever is available, my preference being 1/16-NPT pipe plugs.

The VW engine uses four 5mm plugs; one for the #4 bearing, two for the oil galleries feeding the lifters and one for the oil gallery going to the reservoir(s) behind #2 cam bearing shells. I’ve never found a long plug anywhere except on the #4 gallery but other engine builders have said they’ve seen them installed at the other three locations, sometimes with catastrophic results. A long plug won’t cause a problem with the lifter galleries but even a partial blockage of oil to the reservoirs behind the #2 cam bearing shells guarantees the engine will have a short, unhappy life, since that single 5mm gallery is how oil gets to all eight of the lifters and through them, to the heads.