Elvira : Rebuilding the 36hp, episode 6 : Rocker arm geometry
episode 6 : Rocker arm geometry
Milling the cylinder heads compression ratio might have seemed like a good idea, but now my rocker arm geometry is way off!
Since I've milled 3.2mm into each head, the whole engine is now 6.4mm less large...
So, I gotta shorten them pushrods! (and that's just the beginning...)
On 36HP engines, contrary to more recent T1, the lifter and the pushrod are one single part...
I start by making myself an adjustable pushrod to find out the right length : I grab an old pushrod, cut it in the middle, throw at it a length of threaded rod and a couple of nuts, and I'm ready to rumble.
Next, I install a dial gauge to measure the total lift ; I measure 7.76mm at the valve, which is relevant with what I obtained with my camshaft measuring bench (more on that later).
I then turn the crank until I'm at half-lift (that is 3.88mm) : while in this position, the pressure screw on the rocker hs to be perfectly aligned with the valve stem. Side note: some of you may argue that this shouldn't be measured at half-lift, but at the angle at which the valve has the maximum linear acceleration, as this is when you get the most mechanical constraints. From a mechanical stand point, that's right... But come on, this is just a 36HP, with chewing-gum valve spring, not a 2.4L with adamantium double valve springs running at 8000 RPM. The half-lift willl definitely but a good-enough approximation!
Anyway, I adjust the length of my pushrod, tryin to get the lifter in the correct position... Try, remove the lifters, adjust the rod, put back the lifters... After the 3rd try I had the correct length : 299.2mm, while the pushrods are initially 302.3mm long. That's 3.1mm I gotte take off of each pushrod ; it makes sense, since I got my heads lower by 3.2mm on one side, and 3.15mm on the other.
To shorten the pushrods, I first remove the lifter part : it's pretty easy, you jut need to put the rod in a vise (in between two pieces of wood not to scratch it), and give a firm tap with a bronze piece on the lifter.
The rods are then lathed down, using a W20 8mm collet.
I also remove short of a 1/10th on the diameter over 12mm of length, unless you can't put back the rod into the lifter (trust me, I bent 5 of them trying). I suppose they had a machine at the VW factory that would hold the whole length of the rod to prevent bending.
To make sure the pushrod isn't bent afterwards, I just put it back into the engin case, and make it turn between my fingers : if it's still straight, it will remain centered into the tube! Obviously, don't push it all the way into the case, unless the flat side on the lifter will prevent you from making it turn.
Pour vérifier que la tige n'est pas pliée une fois le poussoir : on la remet dans le bloc et on la fait tourner du bout des doigts : si elle reste bien centrée dans le tube enveloppe, c'est qu'elle est droite! Evidemment, il ne faut pas la rentrer à fond, sinon le méplat sur le poussoir empêche de la faire tourner.
The pushrods on 36HP engines may contain a piece of wood inside (made out of beech wood) : actually that's known to be the only piece of wood in a beetle! (well, if you ignore the convertible tops obviously)
My pushrods didn't have that piece of wood inside ; but I had another one (gift from Eric SIMON) which did contain that rod. But the actual role of this rod has never been really established...
(Edit 20161103 : Oops, forgot to add pictures right here!)
I've read different theories on the subject :
To make oil go up to the rockers thanks to capillarity effect : I don't buy it. No pressure, no flow, and the oil would actually drip back into the rod. Nope, not happening.
Pumping effect due to the wooden rod going up and down into the pushrod... I don't believe it either, there's an actual oil pump pushing behind, I don't see how that would work.
To dampen the vibrations and limit distribution noise by absorbing some of the harmonics : well, why not, could be.
To limit the oil volume in the push rod. Thus limiting the weight of the pushrod, making the whole distribution lighter. Plus, upon starting the engine, you'd have less volume to fill up, meaning faster pressure build up. That could make sense ; the flow is anyway limited by the hole diameter on the lifter and on the rocker side : no actual need for the pushrod to be filled up with oil.
Anyway, as time goes by, these wooden rods tend to hit each side inside the pushrod, end up taking its shape, with the risk of plugging the holes. Therefore, I rather not having them...
Elvira : Rebuilding the 36hp, episode 7 : intake manifold
episode 7 : intake manifold
Same issue as with the pushrods : the intake manifold is now too long to fit, since I've modified the cylinder heads... Gotta admit, I didn't see this one coming!
Since I did not want to modify my original 36hp manifold, I found a spare one on LeBonCoin...
There we go, I cut using a hacksaw, and I remove the dreadful 6.4mm! I take advantage of the accessibility opportunity to clean the inside of the heater tube, which was in dire need of some TLC. Definitely easier to do this while it's opened like that!
I MIG-weld the parts back together... Starting with the thinner, upper tube, the one that brings the air-fuel mixture to the heads.
To make sure to whole thing is air-tight (not easy to make air-tight MIG welds on the first try!), I close up the extremities using bit of a bike tire inner tub ; I use the valve from the same tube to put the whole thing under pressure (cue Queen's music). This gives me a way to pin point any remaining holes, which I grind, weld close, and file again (why on earth did I wait so long to buy myself an electric file??)... On the fifth try, it is air tight. I still have one or two micro asperities, that will be closed by the layers of paint. Plus, while running, the manifold is under depression, not under 5 bars of pressure... (the first one to talk about Jusdon gets a slap)
I then weld back the second tube, the heater one (the exhaust gaz go through this one to heat up the manifold and prevent freezing). This one is easier to weld as it's much thicker, there's less risk to "go through" with the MIG. Therefore I can grind nice chamfers before I actually weld..
But I don't have access to the cut other side of the tube, next to the first tube I welded. I hoped that a nice clean weld on each side would do the trick, but when I wput it under pressure, it was leaking all over the place. So I got the Dremel out, and cut a window to get to the inside of this cut and weld it from there. I welded the window back in place, and this time it was air tight on the first try!
Next step is as usual : sandblasting, 2 coats of rust-preventing primer, 3 coats of paint... And TADAAAAA!! Here's your 6.4mm shorter manifold! Yep, all of the above just for 6 f***ing millimeters! Dayum, you gotta love your compression ratio, right?!
Elvira : Rebuilding the 36hp, episode 8 : cooler, tinware and shroud
episode 8 : cooler, tinware and shroud
I start by sprucing up my oil cooler. I put it under pressure to ensure it is still air tight, using a bicycle tire valve (same method I recently used for my intake manifold). It holds at 5.5 bars : we're good here.
Thorough cleaning using brake cleaning fluid and compressed air, giving the whole damn thing a good shake to make sure I get rid of any muck sitting in all the nooks and crannies inside...
Then I give it a light sandblast to remove the flaking off original paint (I obviously first taped shut the oil in/out holes), and then a thin coat of high temperature spray paint, just to prevent rust. Just to make sure the sandblasting did not affect the oil cooler, I give it another pressure test ; still holds at 6bars, we're still good (#paranoid).
It then goes back on the engine with a couple of brand new gaskets. Next !
Fan shroud and tinware
Again, because of my modified cylinder heads, I gotta touch up the tinware to make it fit the new engine width.
Since I'd rather keep my original tinware untouched, I managed to get my hands on a new set of tinware and fan shroud to modify them. That new shroud is slightly different than my original one, it doesn't feature the top recess (which makes room for the oil bath air cleaner)... Prolly an older shroud ; well, since I wanna move later to a two carbs setup...
For the two over-cylinder tins , it's pretty straight forward : I just Dremel-cut 3.2mm at their base. Done.
For the shroud, well, it's a bit more tricky. I make two triangular relief cuts on each side, which I then bend inward and weld back shut... And there you go, a 6.4mm narrower shroud.
Well, it did take a few hours to weld/grind!
The two tins get sandblasted ; the shroud is too big for my sandblasting cabinet, so I sand it down to bare metal with an electric file.
Then, the usual ; anti-rust primer, some bondo finition (the shroud looked like a mine field), filler primer, sanding, and then finally painting with a two-component polyurethane spray can.
I wanted to give a shot to this product for a while now, as a friend recommended it to me... Not exactly cheap (25€ the spray can at Vernicispray), but I gotta say, the result has NOTHING to do with that of a standard spray can! Shiny! Well, sure, as I used it in my dusty garage, it's not perfect by any means, but way good enough for engine tinware as far as I'm concerned.
In order to use these spray cans, you first have to hit the bottom cartridge, that holds the hardening component, then shake the damn thing a couple of minutes. You than have 6 to 7 hours to use the product before it hardens... So you need a bit of organization if you want to spray more to one coat!
Just one drawback I experienced : it might be because the temperature in my garage was too low, but by the end of the can, it spitted droplets instead of a nice even spray (even though I did heat the can before use by putting it above a radiator, and made sure the nozzle remained clean)... Just be careful.
The oil filler, small tin below fuel pump, and front/back half-moon tins all get their lick of paint as well... I did not originally planned to do so, but they looked dull next to the other shiny parts...
About a dozen years ago, I converted my circuit to 12V, using a rare 90mm generator (ref. VW 113903031E, ref. Bosch 0101206116), and a fitting Bosch 14V 25A regulator (ref. Bosch 0190350049).
But that regulator only held by one single screw on top of the generator, and since it was a bit too long, it had to be set askew... And, well, you know my OCD.
So i took a deep breath, a drill press, and drilled a 4.2mm hole in the generator body (making sure I wouldn't drill into a coil inside, obviously), which I proceeded to tap at 5x80 like the other one. Done! I then gave a lick of paint to the regulator, cut 3mm from its back stand, and now it ssits aligned with the generator. Much better!
As usual, since nothing is ever simple, while putting back together the fan assembly, torquing the nut at 6mkg, the expansible washer broke on me... Argh. Ordered a new one from VW Classic Parts (ref. 111119135), yet another week to wait... Damn, restoring these machines requires infinite patience!
To put everything back together, I ordered a set of stainless steel tinware screws identical to the original ones (mine weren't looking good). The cardboard "seal" between the generator and its stand is glued in place using Gasgacinch.
I also give a coat of satin black on the coil (an actual, real blue Bosch one), the generator's pulley, and the oil pump plate (which I had forgotten, and already showed rust spots).
The coil also receives a sticker reproduction to make it look like an old 6V one... That'll make the trick!
After a bit more of fiddling... TADAAAAA!!
It seriously starts to look like an actual engine, right??
OK, almost there now... If the pain in my shoulder gives me some slack, this baby should run pretty soon!
Elvira : Rebuilding the 36hp, episode 9 : Flywheel and Cluch
episode 9 : Flywheel & Clutch
OK, time to put the flywheel back on... Where is it, by the way?
Confession of the day : I've spent hours upon hours, month after month, looking for my flywheel. I completely emptied my 3 garages, twice, and I was still unable to find the bloody thing.
I finally came to the conclusion that I possibly had thrown it away by mistake (!), and right before I started looking for another one (they're not easy to come by, them 36hp flywheels), I gave a call to my friend Laurent, to ask if I had not left my flywheel at his workshop when we closed the engine block...
I didn't expect much as I thought I remembered him telling me it would be better to keep all the parts together...
But he told me "yes, sure your flywheel is here!!".
GRRAAaaaaRRRGHh!!!! So much time lost! Damn, I could kick myself in the ass! #StupidOfTheYear
On my flywheel, the oil seal running surface was pretty dull : some pitting, lots of oxydation... In order to avoir any oil leakage from there, I had to do something about it.
So I polished the running surface, starting with dry sandpaper 320 / 400 / 600 grit, then with oil (WD40 is your friend) 800 / 1000 / 1200 / 1500 / 2000 grit. I ultimately use 3 polishing compounds, of increasingly finer grit, applied with a felt wheel on my Dremel tool.
I take this opportunity to ever so slightly round the top angle, to make sure the oil seal won't get damaged when putting everything together.
And Tadaaaa! Shiny-shiny!
Now comes the time to adjust the axial play of the crankshaft ; it has to be comprised between 0.07 mm and 0.13 mm, ideally in the lower part of this range, to take into account the parts wearing out.
That's the opportunity for me to bring out my BIG torque wrench, the one I use to reach the 35 mKg needed to properly tighten flywheels and rear wheels' central nut.
First step, find a set of shims, cuz' as expected, the ones I have don't allow me to adjust the play correctly... And as usual, the 36hp shims aren't the same as Type 1's, and much harder to source!
Long story short, I buy a couple of 0.32mm shims from VW Classic Parts, take out the ones in my original engine, and I end up with a pretty good assortment of shims in various thicknesses, plus 3 paper gaskets of various thicknesses.
Without the paper gasket between the flywheel and the crankshaft, I get a little over 0.03mm of end play, measured with a dial indicator. After 4 assembly/torquing/disassembly sessions, I manage to find the right set of 3 shims (always install 3 of them, for relative rotation speed reasons) to get 0.10mm of end play with the paper gasket on. I would have prefered it to be a tiny bit tighter, like 0.08mm, but it will do. I give the oil seal a good dose of lubricant, put the flywheel on, and torque the central nut (with a drop of blue Loctite medium threadlocker).
Just for later reference, if you ever had to look for 36hp shims : here are the VW references. Good hunting! :
111 105 281 : 0.24 mm
111 105 283 : 0.30 mm
111 105 285 : 0.32 mm
111 105 287 : 0.34 mm
111 105 289 : 0.36 mm
You can get reproductions from BBT, but at 6€ a piece, I find it a bit expensive... And make sure you deburr them before use!
The flywheel had been re-surfaced and balanced with the crank and clutch assy (work done by Slide Perf in March 2012!! It's really high time for me to finish this engine! ).
A "1" mark had been stamped to make sure the flywheel is in the same position as it was balanced ; same for the clutch assembly, with a "0" mark. At least, the bloody thing shouldn't wobble around.
The flywheel, clutch disc and clutch mechanism running surface are thoroughly cleaned using brake cleaning fluid before assembly.
The clutch assy screws are torqued (2.5 mKg) and secured with the usual drop of Loctite.
That's it for today! Yet another checkbox ticked out!
Hopefully this engine should run in no time now! (wishfull thinking...)