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.

AV -- CRANKCASE BASICS

I was dismayed to learn that some folks having no Volkswagen engine experience have been buying components, mostly from ads in car magazines, expecting to simply bolt things together, hang a propeller on one end, an airframe on the other and go flying. In at least one case a fellow thought he could buy a bunch of parts, haul them up to my shop, wave a lot of money at me and drive off with an assembled engine.

It simply doesn’t work that way. Here’s why:

When you buy a new crankcase what you’re actually purchasing is a ‘universal REPLACEMENT crankcase.’ These were originally provided only to VW dealers, where they were used for the repair of an existing engine whose crankcase has cracked due to age-hardening or collision damage. As received, your new crankcase can’t be used to build an engine from scratch because it is not complete. What’s missing are the things that make the crankcase specific to the vehicle Type and the model year. There is no sump-plate or oil screen, no studs for the oil pump nor fuel pump, no head stays (ie, studs) and no nuts & washers for the studs that are there. You’re expected to remove all that stuff from the original engine, the one with a cracked crankcase.

You can buy all the missing bits either in kits or per-each but if you’re building a flying Volkswagen you’ll be pissing away a lot of money because the parts in the kits are specific to automobiles. For example, in the standard ‘case kit’ (about $20) you get the oil control pistons, springs and slotted cap-screws. But for a flying Volkswagen you need a cap-screw you can safety-wire and an oil pressure relief spring that pops-off at 45psi instead of 27. You’ll also get a mild steel cover-plate for the big hole in the lower right corner of the sump where the dip-stick attaches on the Type III vehicles. Which goes straight into the trash because it weighs three ounces and one made of aluminum weighs barely half an ounce. Ditto for most of the studs since you’ll be using drilled-head bolts which you’ll have to procure and drill yourself. Bottom line is that it generally costs less to ignore the kit and buy the parts onsey-twosey.

A head-stud kit consists of the sixteen stays (in three lengths) that secure the heads to the crankcase, along with the required washers & nuts. Unfortunately, oft times one of the studs or nuts won’t have any threads and you end up having to beat the bushes for a replacement, since any effort to have the retailer replace the kit is like pissing into the wind. Indeed, you’ll often receive a head-stay kit clearly marked as being for a single-port engine that turns out to have the four short stays for a dual-port.

Even when you receive the proper head-stud kit, the things are bare metal. Before you can use them on any properly built engine they need to be plated, painted or coated - - and done well enough to withstand twenty years of exposure. (I usta have all my head-stays cadmium plated but when the tree-huggers forced the local plating shop out of business I went to two-part epoxy paint. Most recently I’ve been using powder coating.)

Finally, you will need nuts and washers and bolts to fasten the case studs and parting-line. Here again, there are kits available but most are the shoddiest stuff imaginable and price is no guarantee of quality. The nuts and washers may have a wash of zinc plating, good for at least a week’s exposure to the weather. Or they may not. And you can toss the ‘exhaust nuts.’ They are copper plated steel. (The good stuff is bronze.) Before you can use any of this crap on an engine you must provide it with some form of corrosion protection. If you don’t, not only with the nuts rust to the studs, you’ll see galvanic corrosion between the washers and the crankcase that will eventually cause the fastener to loosen.

But the biggest problem is that your new crankcase is for a stock ‘1600' engine. Flying Volkswagens tend to be larger, which means the crankcase must be machined to accept bigger jugs and, in some cases, a crankshaft having a longer throw. Plus it needs a critical bit of welding .

In the stock crankcase the spigot bore for the #3 cylinder is sort of hanging out in space. Even on the stock engines this area is prone to cracking. Indeed, a ‘cracked #3' is one of the most common reasons for the existence of Universal Replacement Crankcases. Machine the case to accept bigger jugs and you’ve made the situation worse by an order of magnitude. It’s no longer a question of IF #3 will crack but simply ‘when.’ To deal with that you preheat the new crankcase case and weld in a reenforcing plate using TIG.


A 94mm barrel will hit the threaded steel inserts that are standard on all new crankcases. Not only must you open up the spigot-bores to accept the larger barrels, you must deck the case to provide a uniform sealing surface for the bigger barrels. Since decking the case moves the heads closer to the centerline of the engine, it upsets both your valve-train geometry and your compression ratio. Because of the normal variation in the size of after-market parts, resetting both the CR and geometry is best done by inspection, meaning you’ll need to devote a couple of pre-assemblies to each of those procedures.

Opening up the interior of the crankcase to accept a bigger crankshaft is called clearancing and while most shops use a humongous cutter to do the job at one go it leaves a lot of feather edges that are guaranteed to precipitate cracks, so you have to dress the edges smooth by hand, using a flapper wheel, files and #600 grit sand paper.

If you’re doing the HVX mods you need to pull the plug from the oil gallery on the right-hand side of the crankcase, extend the existing oil gallery and connect it to the #3 cam bearing saddle. This is when you also open up the oil channel behind the #2 & #3 cam bearings (which is how all of the oil gets to that side of the engine.) If you’re installing anything in the distributor hole other than a plug you must also do the grub screw mod.

If you’re going to install the oil temp sensor in the location used by Volkswagen you need to pull the 3/4" plug to the lower-right of the oil pump and thread it to accept a 1/2"-NPT x 1/8-NPT adapter. The oil temp sensor then threads into the adapter.

If you’re running a full-flow oil filtration system (and you should) you tap the main oil gallery to accept a 3/8-NPT to AN8 (flare) adapter. Some engine-builders also thread the oil gallery leading from the oil pump to accept a 1/4-NPT pipe-plug.

If you’re going to run an external oil cooler you thread the oil cooler ports to accept pipe plugs.

And having done all that, it’s time to clean the crankcase.

No, you can’t just blow it out with compressed air. There are a couple of blind corners in the oil galleries that act as swarf-traps. To clean them out you must pull all of the soft aluminum plugs (except the two small ones associated with the oil pressure valve... you can check for contamination by using a mirror down the bore of the valve) . After pulling the plugs you tap the oil galleries to accept socket-head aluminum pipe plugs of the appropriate size: 1/16, 1/8, 1/4 and 3/8. Now you can scrub the bores and visually inspect them.

As with the ‘case kit’ You can buy a ‘plug kit’ but they don’t include the four 1/16-NPT’s you’ll need for the 5mm plugs. Instead, they’ll sell you eight 1/8-NPT’s and shug; that’s what they use in dune buggies.

And finally, once all the machining is done and the case is cleaned and sealed up, if it’s a magnesium case you paint it. Because if you don’t, it’s going to corrode. Use regular flat-black Rustoleum. If you can’t get flat-black use gloss-black cut with a little naphtha. (If it’s an aluminum case you apply Tech-Line Coatings ‘TLTD’ thermal dispersant then bake the thing in an oven not used for food preparation.)

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So what’s all that going to cost you? Dollar wise, it depends on where you’re located and how much of the work you can do yourself but at a guess, expect to pay between $150 and $400 over and above the cost of the crankcase. Here in southern California there are several good shops that do nothing but high-performance VW engines. In other parts of the country I know of guys who have paid twice as much and gotten less for their money. If you’re tooled-up to do the drilling & tapping you can cut the cost by as much as $200.

And that’s just for the crankcase. The cylinder heads, crankshaft, camshaft, pistons & cylinders, push-rods and push-rod tubes also require a significant amount of preparation before they’re ready to be used.

So hold your horses. You are not building a dune-buggy engine. You’re building an aircraft powerplant meant to deliver at least twenty years of reliable service. In future posts I’ll show you how I do it - - and why. It’s up to you as the Mechanic in Charge of your engine to decide if you want to follow suit.

-R.S.Hoover

AV -- CARB HEAT BOX

When fabricating a carb-heat box one of the trickier bits is the axle on which the flap or air-vane pivots. Most start with a round rod then file or mill it flat on one side to accept the flap. The axle now assumes a D-shape and the flap is attached to the flat part of the D with rivets or screws. A few use steel and weld flap to the shaft, trading the heavier weight for the greater ease of fabrication.


To actuate carb-heat we must cause the air-vane to move. An interesting point, often overlooked by the novice, is that the flap or air-vane need not swing through a 90 degree arc to let hot air into the box. If the hot air source is fed into the side of the box perpendicular to the normal air flow, any angle greater than 45 degrees is sufficient for the carb to draw-in 100% heated air.

The usual method of causing the air-vane to move is to attach a lever to one end of the shaft to which the air-vane is attached. The tricky bit is to do so in a manner secure enough to risk your life upon. The most popular method appears to be to continue the D-shape to the end of the rod and to make a matching D-shaped hole in your lever. At his point the novice is liable to give up because producing an accurate D-shaped hole with hand-tools can be rather difficult. Some convert the D-shape of the axle to a square shape, since it’s fairly easy to square a round hole. Of course, if they started with quarter-inch rod they end up with a rather small square - - just .177" on a side; about 11/64". With a trunion that small, if the rod is aluminum or brass you can’t put much stress on the lever, which is why a lot of guys go to a steel rod - - and weld the flapper to it. Or end up using a larger, heavier rod.

I’ve a hunch you could fill a fair sized book with the variations on this theme. And I know a few guys who have done exactly that, bouncing back and forth between the need for an air-vane that pivots smoothly, a lever that provides fail-safe actuation and the need for the thing to be fabricated with basic hand tools. The results are often blindingly complex, with stepped shafts, ball-bearings, adjustable linkages with ball-end fittings and... Most homebuilders fail to notice that in creating such marvels they’ve given up flying for designing.

The method I use is so crude it makes real engineers cringe, but it’s reliable, inexpensive, low in weight and easy to fabricate. While the 'experts' are peering down several yards of nose, talking about 'trophy points' and 'state of the art,' you're actually flying.

I make the axle out of square rod rather than round. The basic idea here is that a square rod will rotate smoothly in a round hole having a diameter equal to the diagonal dimension of the rod. This method works because the rod only has to rotate about a quarter-turn to do its job; it doesn’t have to rotate fast nor often. For a rod that is one-quarter inch on a side, a size ‘T’ drill makes a hole that is a pretty good fit. To make the square hole in the lever you simply begin with a hole 1/4" in diameter and use a rat-tailed file to give it four corners. Since you have the square rod as a gauge it’s pretty hard to go wrong. A washer and cotter key then serves to retain the lever.

There's a bit more to the actual fabrication of course, details specific to the carburetor, method of mounting the engine to a particular airframe and so forth. The purpose of this post is to make you aware of the principle - - that a square shaft can rotate smoothly in a round hole.

Need I mention that this method works equally well for cabin heat or controlling the flow of air through an oil cooler? Probably not :-)

-R.S.Hoover


PS -- This method isn't new. I first saw it in the 1940's, on a rather ugly flintlock rifle manufactured in the back-woods of Pennsylvania in the 18th century. The fact the rifle was still shooting 190 years later served as a nice lesson in the practical value of low-tech simplicity.