Skip to main content

Sorry for your trouble Stan but I count it as good news those one-off(?) heads are back in your possession. I'd been trying to envision the wily Beetle freak Postal Worker who spotted them as Type 1 parts, filched them, then examined them on his home bench only to realize he'd snagged the friggin Hope Diamond. Next time we meet lets drink three beers and work out a movie script about his efforts to surreptitiously return them to the regular mail stream. I will have my people contact Wayne Knight's people.

The saga continues.

The 2234 shortblock has been assembled for months with Dan Ruddock's custom Web cam.

Progress on the heads has been slow but steady. They are finally complete-- the port cleanup is done, the 3-angle valve-job is complete, the chambers CCed to within .2 of each other (after flycutting and sinking one of the valves a bit), the PTFE valve-seals are installed, and the beehives are all at the appropriate spring height with a shim under each of them (for wear). Seat pressure is 115- 118 lbs, so we're exactly where we were aiming. We've done pretty much everything twice to ensure that they are as close to perfect as any custom thing can be.

Everything was tracking smoothly to finally button this up, right up until the time Jason degreed the cam... and found that it had been ground on two different centerlines. The day Jason found the problem was one of the worst work-days I've had in the last 5 years-- and if I'd have had a dog, I might have kicked it. I think the thing that really bothered me was that all I ever hear is how super-nice Web cams are, how great the ramps are, etc. It may be true, but this is the 3rd Web cam that a builder has found ground wrong while building an engine for me (two 86b cams had the exact same issue when we were building the twin-plug motor). I've yet to actually run one in a Type 1.

I knew the case would need to be split again to replace it. Because when it rains, it pours-- the (incorrect) cam I had was the last of these super-special custom cams out of Dan Ruddock's stock. To complicate the matter even further, Web got way, way behind on orders during the COVID shutdown, and is struggling to catch up (which is why Dan is out of stock). The case was split, and the cam boxed up and sent off on Tuesday.

I was really "over" the whole Web Cam thing, and ready to buy a set of Pauter 1.4 rockers and put the CB 2292 cam back in the case, in the interest of continuing forward progress on this particular science project. But I was told that because of my situation-- I'd be able to cut to the head of the Web cam line, and thus talked back from the ledge. I'm still wondering if I shouldn't just sell several gold fillings and order a JPM cam from Sweden (although my super-great experience with international shipping chronicled on page 5 of this thread has me a bit gun-shy). I'm wondering how, after 60+ years of serious hot-rodding on the Type 1 VW, we can still be in the experimental stage of camshaft development.

I went through the 5 stages of grief: denial, anger, bargaining, depression, and acceptance. In the end, I decided to just wait this out for now. We sent the cylinders out for a perfect hone because we've got nothing to do until we get a new camshaft. This was my idea. I'm pretty sure this is just more excess, but if I have blow-by with the Deeves rings, the Total-Seal seconds, the valve-seals, and this super-duper hone job-- it won't be because I cheaped out. It made me feel a little better to throw some more money at it, but it doesn't change the fact that we're dead in the water until the cam comes back.

... and that's kind of the theme of this project. Even when a guy wants to do something all the way, and is willing to pay for it-- there are no guarantees in VW-world. This is the very definition of a "boutique hobby", rife with all the problems that can be encountered by trying to get parts from disparate places to play nicely together. I've not even begun to contemplate how long it'll take to get this engine running should I choose to go ahead and do EFI, but I would suppose it will be every bit as challenging.

That's all the news that's fit to print. We haven't stalled on this project, but progress has ground to a halt for the time being.

 

Last edited by Stan Galat

Those are good questions, @edsnova.

The shortest answer I can provide is to say that as important as they are, camshafts are probably the least understood (really truly understood) parts of an internal combustion engine, at least for most of us. It's clear that automotive engineers in manufacturing understand a lot more than hobbyists, because they've been developing variable valve timing strategies for decades. They understand what is happening inside the combustion chamber and are making adjustments accordingly.

A "hot-rodder" (which is what we are, really) is left to extrapolate and experiment. Cams are ground and installed, hoping that they will exhibit the characteristics the builder is aiming for. There are many, many variables that go into the design.

Most of us (and you for sure) understand that the lift and duration determine where the power occurs and how much power is available.  But the shape of the lobe, when each valve opens relative to each other (and at what point in the 720* cycle) are very important as well.

The shape of the lobe is why people rave about Web cams. A camshaft lobe can be shaped almost like a box, with very steep opening and closing ramps and a blunt (almost flat) nose-- where peak lift is maintained for most of the intake cycle. This is how roller cam profiles are shaped, and is one of the main advantages of using them. Other cam profiles are shaped more like a splitting wedge, where the opening and closing ramps are slower, but where peak lift is only maintained for a very short period of time. It would seem like getting the valves open as quickly as possible, and keeping them open for as long as possible would be most desirable. There are cams that do that (the FK4X series cams from Engle, etc.). These cams make a lot of power, but they're hard on parts and really noisy. It takes a lot of valve-spring to keep everything in constant contact.

The pushrods in a Type 1 are very, very long, and the rocker arm shafts are really pretty flimsy for what they are being asked to do (2 bolts hold the whole assembly to the head). When you run heavy springs (K650s, etc.), it introduces a lot of stress to the system-- pushrods need to get beefier, rockers need to get a lot stronger, straight-cut cam gears are a necessity to keep the cam from actually being pushed against the thrust bearings by a quieter helical cut gear set. Cam lobes will often go flat.  All of the HD parts weigh more and have more inertia when in motion, so it takes ever stronger springs to keep them under control. It's pretty easy for everything to spiral out of control, and the problems all begin with the shape of the cam lobes and how much valvespring it takes to control the moving parts.

So, an ideal lobe has ramps just steep enough to get the valves open quickly with a lot of duration at peak lift. What this looks like is the secret sauce, and everybody has a different answer. Most of the Engle profiles were copied from Detroit V8s back in the 60s-- there hasn't a been a history of sophistication in Type 1 cam profiles. Johannes Persson (JPM) in Sweden has developed his own cams with great lift profiles, which can be used with relatively light springs. The downside is that they cost $700 fob Sweden, which is about 7x what an Engle or CB cam costs. They do include matching lifters, so there's that.

Duration is how long a valve is open, independent of everything else.Duration

From the Summit Racing website (please excuse the klunky prose):

"Advertised Duration is the degrees of crankshaft rotation that the lifter is raised more than a predetermined amount. This predetermined amount varies between manufacturers.

Duration at 0.050" is the degrees of crankshaft rotation between when the lifter is raised 0.050" and when it is 0.050" from its resting position. This is standard among all manufacturers. You should use this value to compare camshafts."

The duration at .050" as compared to advertised duration will give you some idea how aggressive the ramp is on the cam. If the numbers are relatively close, the ramp is relatively steep. If they're not, the lobe profile is less aggressive.

Another thing most guys (me included) don't readily understand is lobe center separation. This is what you were asking about, and this is what was wrong with the Web cam I got from Dan Ruddock. The Lobe Separation Angle determines where the lobes are positioned in relation to one another. Lobe separation determines overlap (how long both the intake and exhaust valves are open at the same time. Generally speaking, narrower lobe separation gives more torque, greater lobe separation gives more upper end horsepower. CB cams are ground on 107* lobe centers (separation angles), Web and most other VW cams are on 108* lobe centers, and LS V8s cams are generally on 112* lobe centers. twolobes

 

The last thing to think about is when the cam opens and closes in relation to the position of the piston. In the drawing above, the cam is "straight up"-- the center of the cam overlap is at TDC, and the distance (in degrees) between TDC and the lobe centerlines is equal. Most cams are ground with some cam advance built in, so that the distance between the lobes in relation to TDC is not the same. This is where adjustable cam gears come into play-- some minor (+/- 4* typically) adjustment is built in so that the cam can be "degreed" to match the cam card (provided with the camshaft) perfectly. This is probably the most important step in blueprinting an engine, and most decent builders will do this even if they do nothing else.

The problem with the Web cam I had was that the lobes were ground on the wrong centerlines. The intake was fine, but the exhaust was 7* late. This would mean that my lobe separation angle was wrong, the overlap was greatly increased, and the cam timing was all wrong. The engine would've run, but not very well. It's a pretty big deal.

I'm not sure if this answered the question, or if it was more like trying to sip from a fire-hose... but with this engine, we've obsessed about a couple of grams of rotating mass, and .2 CC in combustion chamber volume. The camshaft and heads determine the characteristics of the engine. I want the most important single component of the engine to be right. 

Attachments

Images (2)
  • twolobes
  • Duration
Last edited by Stan Galat

Thanks for that, Stan. Very useful cam theory detail. Your second from last paragraph is what I was looking for; trying to extrapolate whether you’d have piston-valve clash or other broken parts scenario.

and I asked since it’s probable that most builders would never notice this mfg error in assembly. Who checks to see that the intake and exhaust lobes are actually ground from the same centerline?

I’m thinking almost anyone else would’ve got it together, started it up, and subsequently gone crazy trying to get a good tune. But how would it have behaved? Weak bottom end? Low compression? Pinging? Strong to 5k then lays down like a baby?*

As you say, it’s just one more hazard for the typical hobbyist.
==
*I recall a big block chebby build Car Craft did in the 80s that did that; turned out the cam mfg shipped the wrong valve springs. No one was the wiser until the third pass down the quarter mile.

 

 

Sorry about that, Ed. I figured you'd know what was what, but I wanted to get it all down. Chronicling everything may help provide medical personnel a paper-trail for some context when they start my treatment and medication regimen. 

So to answer the direct question directly-- I don't think anything would hit, because the lobe centers were getting further away from TDC. I would like to think that any engine builder being considered by guys here would degree the cam, but I know there's a lot of hacks out there looking to low-ball a "build" (which is really more like an "assembly").

I have no idea how it would have run, other than "not well". I would imagine there'd be quite a reversion issue.

Last edited by Stan Galat
@Stan Galat posted:

 

 

twolobes

 

The problem with the Web cam I had was that the lobes were ground on the wrong centerlines. The intake was fine, but the exhaust was 7* late. This would mean that my lobe separation angle was wrong, the overlap was greatly increased, and the cam timing was all wrong. The engine would've run, but not very well. It's a pretty big deal.

 

I like to belabor things I don't fully understand, either until I do understand them or until the person I'm belaboring gives up and either walks away muttering (good) or lies and tells me I got it (bad). This is the secret to my misplaced confidence....

Anyway—and thanks again, @Stan Galat, for your insight and instruction—are you sure a 7-degree later exhaust cam timing would increase overlap? Because my eyes tell me, according to the above diagram, that clocking the exhaust lobe rightward a little would decrease overlap, which my tiny brain suggests would increase your effective compression ratio while (perhaps) causing more spent exhaust gases to hang around the combustion chamber.

My guess is that would be bad for an engine built with high static compression.

I see what you are saying, Ed, and I think you're right. The overlap looks like it would decrease as the lobe separation angle increases.

My curiosity generally ends at the exact point where I figure out that something is not right. Once I determine a part has been made incorrectly, I don't think much further about how things would behave with the incorrect part (which makes me a dullard, I suppose). I can't unsee, ignore, or forget about it-- it's a burr under the saddle that bothers me until it's set right.

What's curious to me is the effect that increasing/decreasing lobe center and the cam itself being advanced or retarded from the TDC/BDC centerline has on the powerband. I once ran a cam with a bunch of lift and a fair amount of duration ground on a 105* LC. It was meant to "tame" a giant set of heads, and failed pretty miserably in that regard. I also ran an FK8 advanced a couple of degrees from the cam card that ran like a scalded dog, but suffered from preignition.

These are games guys way smarter than me play around with to see what will happen. I don't know of anybody that would go to all the work to see how something obviously ground way off would work, although it would be really interesting from an academic standpoint.

There's an awful lot about camshafts I don't know. I really wish I knew more-- but I suspect that it's a bit like saying, "I really wish I knew more about how the pancreas worked". Cams are probably an entire field of study unto themselves, and I would suspect that there are dudes hiding deep in the bowels of car manufacturers who have devoted their entire careers to understanding them more fully. I don't need that level of expertise, but I have a lot of questions (Why are most cams ground with identical intake and exhaust lobes? What's magical about 107- 122* of lobe separation? etc.).

There's always something to learn.

 

Last edited by Stan Galat

Add Reply

Post Content
×
×
×
×
Link copied to your clipboard.
×
×