Cam specs: what's the best for high RPM power?

48 mm x 40 mm?!?

Unless they're Comp Eliminators or Pauter or JPM heads with HUGE ports, there's no way the heads themselves can support valve sizes - to say nothing of the fact that they'd be impossible to control unless they were titanium valves, and they'd still need springs strong enough that I'd be worried sick about wiping out cam lobes.

A 40 mm carb set would be grossly undersized. They'd need modified 51.5 mm IDAs, and they'd still be undersized.

I'm not sure a 1-7/8" header would support them. I've seen headers with 2" primaries advertised - I'm pretty sure you'd need them.

I think Johannes Perrson built a 220+ hp 1776 with a setup that spun to 9000 RPM, if I'm not mistaken. It's a crazy-expensive way to make power.

Ed- for starters- ideally, the heads are wayyy wrong- they're big displacement/very high rpm, run on race gas race heads which on a half pint motor, even cammed to make power to 7500-8,000 rpm (think Webcam 86C- 274?° @ 0.050" will have a very narrow powerband (all top end) and, won't be a lot of fun to drive on the street without close ratio gears .  Your 140 hp lower benchmark could be achieved with less duration (262 @ 0.050") but now it will probably ping on any street gas you can give it.

A set of Panchitos (40x35 mm valves) are capable of producing 170? 180? hp and are more than enough for any 1800-ish cc engine and my recommendation to anyone trying to build a street engine with these heads is to sell these race only, huge valve monsters and buy something more appropriate for a smaller engine .  Any cam/rocker combo with 258-263 (140hp)- 268-ish (155hp) degrees @ 0.050 with a little over ½" lift will be perfect.  With the smaller cam (FK-8, W125, 86B) 9.5:1 is pretty safe, 10:1 if you really know what you're doing and with more duration 10¼- 1½:1?

If one absolutely had to use those heads for a street engine- DISPLACEMENT IS YOUR FRIEND!!!  The bigger the better.  And since those heads may not have all the cooling fins that street heads do, it will probably be easy to overheat them on the street, so a cht gauge will be necessary.  This will be a GREAT Friday night to the drive in and late night street racing engine!!!  The V8's will fear you _{(think big evil laugh!)}

These heads are still too much for even a fairly big street engine though- ideally valve sizes should be 42-46x 37.5 to have some semblance of the bottom end/lower midrange smoothness for that drive to the burger joint...

What if I told you a .394 lift cam for this combo made 144 HP at 6400 RPM, with 128 lb-ft at 4800?

No pinging. I don't know the duration but I think 260-ish is probably in the ballpark.

To make more power (on a slightly different engine of similar displacement), the cam lift was increased to about .500. The engine made 155 hp at 7600 with a torque peak of 128 at about 5200.

Obviously, to Stan's point: yes, the valves are way too big for an engine of this displacement, and anyway can't rightly fit in the Type 1's combustion chamber.

And, AL, yes, everyone knows the Panchitos are the way forward.

My question is about cam specs tho. We all have ideas about what's "right" for a certain combo. Some time ago people here were surprised by the relatively large cams being run by Pat Downs on a 2332 with smaller heads and valves, because it didn't track with what we all thought we knew. I was fascinated to see how small the lift was on this particular engine, and yet how high it revved with power.

To be clear: the heads on it were factory. It's an old school setup.

I think it would be interesting to calculate and/or test the flow rates of these combos against a more modern hotrod 1776 Type 1 with commonly available heads and valve sizes. Say, 42 and 37.5, then adjust lift and duration to see what it would take for the smaller valves to flow the same numbers.

I'd predict a convergence. But since we so seldom talk about valve sizes and combustion chamber shape (by comparison to cam specs), I don't know.

I assumed we were being led along a primrose path, Ed, and that you had something up your sleeve. There was too much weirdness in the engine in question.

There were a lot of experiments in the internal combustion world before everybody arrived at formulas that work well in every engine. This particular engine either predates or ignores those formulas. It seems like it worked out, but the dyno doesn't tell the entire story.

Everybody always says "the power is in the heads", but in these antiqued engines it's down to how the heads and cam work together. Guys way, way smarter than me are getting really good flow numbers through really small ports and valves, which keep velocity up and power strong even with more cam duration than seems prudent in a street engine. This engine is the opposite of that - huge valves, tiny cam. What this engine would lack, I'd guess, would be enough port velocity to make it "snappy" on acceleration, but I'm speculating.

15 or 20 years back a guy named Jim DuBois was posting here - really innovative guy who was building a lightweight pan-based speedster with an aluminum subframe and a huge (2387, if memory serves) engine with Pro Comps and an 86a cam. It was the same idea - huge ports and valves, really undersized cam. Al Merklin ended up buying and building the car, and commented repeatedly how the engine was too much for the chassis. I never could reconcile that with what I "know", but it's still filed away back there in the archives of my mushy brain.

Back to the way forward - the Panchitos Pat Downs designed are phenomenal heads, but the heads he's turning out now at Pat Downs Performance are even more amazing - huge (200 hp level) flow through a 42 mm valve, etc. Smaller, lighter valves means less valve spring to control the valve, less wear on everything, and less heat. Pat Downs has singlehandedly moved the hobby 40 years ahead in less than 10 years.

The fact that old-timers got 140 hp out of 48 mm x 40 mm heads just shows how far we've come. If I were guessing, I would surmise that they only lifted .394" (probably at the cam, x 1.1 or 1.25 at the head) because controlling those valves would have required a spring that didn't exist when they built it... but what do I know. I'm just a great ape with a keyboard.

You smaht, Stan.

Fact is, I was stunned by the small cam (that's .394 at the valve, btw) years ago when I stumbled on this compare/contrast post from Wilhoit. Back then I was just amazed that such small cams revved so high "with power" (as @ALB says), and I didn't even notice that the valve diameters and ports were manhole sized.

I only noticed that today, after posting the specs and checking to see if they were even possible with off-the-shelf Type 1 heads. They aren't. Closest I could find were some very expensive Type 4 heads.

I was also struck by the fact that the .394 lift cam—tiny by our standards—was so close in power and RPM to the .500 lift cam, which would be considered a pretty big cam on most of our engines. Most of the engines people in this group run are bigger than the small cam and smaller than the big one, in this example.

You've thought more about valvetrain dynamics than most of us here, so I can only salute, and maybe add to the massed evidence that big valves—so key to racing and rodding in the not-so-old days—are actually a mistake for street car guys. Because mass matters.

—And because torque down low (which port velocity aids) matters.

And because the sheer size of the big valves can create ...issues.

Yesterday I stumbled upon this video, featuring a long-time Mopar hotrodder tearing down an old Hemi that dropped an exhaust valve.

It was the first time I ever saw an old school Hemi's innards. It was fascinating to see how the two rocker shafts work to do the same basic thing Fuhrmann accomplished with four cams plus four drive shafts and bevel gears.

How the valves take up so much of the combustion chamber. How the chamber is made larger to make room for the valves.

And of course all the OEMs moved away from this aesthetic as they endeavored to make more power in the 1990s. Chevrolet's small block performance head for the 1995 LT-1 had nominally smaller valves than the 1970 LT-1. But hardly anyone will claim the earlier version of the engine was stronger. Certainly no dyno will.

And, Al, you're right too: there's not much point in running a high-strung, small displacement engine on the street when so much more low end torque is available via our friends the cubic centimeters.

So it does seem that our little corner of the hotrod hobby is following the trends set by OEMs, in that smaller heads, smaller valve and bigger cams are, in general, the order of the day for hotted-up street-driven Bugs.

It seems there really is a good reason we don't see many 140-hp 1776s.

think Johannes Perrson built a 220+ hp 1776 with a setup that spun to 9000 RPM, if I'm not mistaken. It's a crazy-expensive way to make power.

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Yes I have seen these motors, since I know Johannes, and actually they wind to 10.5K.

But theses are drag race motors and not drive-able on the street !

  ReV

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Geez guys, it's most of the way through June - smack in the middle of the driving season - and no time for a discussion like this.

These are things to ponder when you're huddled over the fire, wet socks drying on the stove, with two feet of slush and ice in the driveway and two feet of blue toenails in the living room.

Theory may be nice, but what we've got here (well, what most of us have here) is awkward gearing that wants more low-end torque than high-end horsepressure. And engines that scold us at high rpms.

At anything close to 5000 rpm, my type 1 is giving me angry sideways glances and asking just what exactly is going on here and how long do I expect this to continue?

Granted, it's a nice academic discussion to fill some idle hours, but, at this time of year, why are youse guys so idle?

.

What a beautiful technical discussion !  Plus no drift yet ! Please continue !  Can't go out and play with my car yet and we are still having June Gloom here in Socal.  if I can grab the bag of chips away from my Wife, I'd like to sit back and listen to more of this from you guys !..........Bruce

So how about we continue? Let’s say, for some reason, you’re limited to 2 liters. You want both the most low/midrange torque and the best possible top end. Not worried about the budget. Starting from scratch with a new alum Type 1 case.

What do you fill it with and why? Bonus points for using specs and/or dyno results from known engines.

Will 2109cc be acceptable, Ed? That's a slight stroker of 76mm x 94mm barrels. The only case machining work be for the 94mm barrels to fit. 76mm stroke usually requires no case work. CB sells such a "drop in" kit.

Put in a forged counterweighted crank, and forged 5.4" or 5.5" rods. With longer rods and "b" pistons, no cylinder spacers needed. In fact, the cylinder bases may need a cut to get optimal deck height.

High torque needs three things: high static compression, good port velocity, and high lift cam/rockers.

Put in some 1.4 or 1.5 rockers. Web 86c. Static compression over 10:1. Big static compression is offset by the big cam/ rocker combo to give a reasonable dynamic compression. Panchitos and 44 IDF with 36mm chokes. Panchitos would have the chambers fly cut into the low 50-something cc range.

A good 1.5" or 1.625" 4-2-1 exhaust.

Torque and REV to 6500 rpm with power. Don't forget to get the rotating assembly indexed and balanced.

Not much different than my 2165cc. Also,  very similar to six cylinder 911 high compression motors of 2.7 to 3.0 liter. They make 275-300 hp so take off 1/3 the power for the type 1.

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I think I would be asking different questions.

Like, how much power can you make in a Speedster engine compartment before you exceed the limit of typical oil coolers to keep the heat under control?

Or, how far can you push the limits before engine longevity suffers too much?

If you're building for the street, you just gots to know.

We hear about 'drag race' engines. But, what exactly is that?  An engine that makes great power near the redline, but hardly pulls at all down low? Or one that can only make the power it does for a limited time before it blows up? So, where do the lines get drawn between track monsters and the ones you can take home and introduce to the folks?

And while heat dissipation may be less of an issue in a Spyder, are normal, everyday citizens routinely running over 200hp in air-cooled Speedies and sleeping soundly at night?

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Along the same lines as Danny said- Short rod (356/912 length- 1? 2? mm shorter than Type 1) 74x94- 2054.  As Danny said, Panchitos, 44IDF's, and cammed to how high you want it to go.  FK8 at 9.5 or 10:1 will rev to 6500 rpm and make what, 165? hp, be still really torquey and be still relatively reasonable for maintenance.  FK10 (10- 10.5:1)  will go to over 7,000 with another 10 hp, and be close to the limit of the heads.  Either of these will be MONSTERS (as Danny can attest) in a Speedster or Spyder.  If you can make the engine bigger it'll just get that much better! _{(think big evil laugh here)}

One caveat (ok, maybe a couple)- At 2 liters and bigger, even something that goes to 7,000 rpm with power will have reasonable bottom end/lower midrange and life if you don't drive the bag out of it constantly (just don't rev the sh*t out of it from the moment you start it 'till you shut it off- warm it up before playing and be discretionary of who you humiliate)  Make sure you get valve geometry right or guide/seat life will absolutely suck and also expect to replace valve springs more often- the more and higher you rev an engine, the faster the springs wear out.  Sorry, they just don't last forever like stockers.  You'll probably have to work to get the heat under control (and if you don't, engine life will suck).  Also, to get the best out of an engine like this, close 3rd and 4th gears are a plus (especially with the FK10), so be prepared to accept the Way of 5 if it needs to still hit the highway...

You WILL be feared at the local burger joint on Friday nights after the first couple of dustings..._{(just add the big evil laugh AGAIN)}

And pay attention to what Mitch said above- he's got some good stuff there.  And Danny too.  And if you go much bigger in displacement you'll find that the Panchitos aren't big enough.  And...

@Sacto Mitch posted:

.I think I would be asking different questions.

Not surprising. That's what we like about you.

@Sacto Mitch posted:

Like, how much power can you make in a Speedster engine compartment before you exceed the limit of typical oil coolers to keep the heat under control?

I'm out here on an island, but I think the answer to that is "a lot less than anybody is willing to live with". It's no just the oil coolers that suffer for a lack of air in the engine compartment (as a matter of fact, I think the bulk of oil cooling is best done by means of a remote oil cooler, mounted... well... you know... remotely. There's not enough air getting into the engine compartment for the needs of the engine itself, even at moderate horsepower levels.

@Sacto Mitch posted:

.Or, how far can you push the limits before engine longevity suffers too much?

I love the T1, but it's a flawed design, right from the start. 3 main bearings are probably at least a couple short of ideal. Add in that the cases become distorted as they wear, and the platform has problems. The guy with the million mile European car is not driving an early Beetle.

Given that the platform is flawed, the line between "requires care and feeding" and "that wasn't a good idea" is surprisingly fine. I've been across the line a couple of times. Staying on the right side of the line makes for a happier driving experience.

@Sacto Mitch posted:

.We hear about 'drag race' engines. But, what exactly is that?  An engine that makes great power near the redline, but hardly pulls at all down low? Or one that can only make the power it does for a limited time before it blows up?

Yes.

@Sacto Mitch posted:

So, where do the lines get drawn between track monsters and the ones you can take home and introduce to the folks?

When you find out, let me know. I've had no small number of "swing and a miss" attempts to find the line and stay on the side of the angels, only to be surrounded by pitchforks and horns.

There are 200 hp motors you can take home to mom, but only if mom was a headbanger.

The Webcam cited, with 1.5 rockers is .585 lift (with 1.4s its .546). That's a lot of valve lift!

I like the detail in Danny's answer, but 2109 is 2.1 liters, bigger than 1999ccs, which is the biggest "under 2-liter" displacement.

What if there was a racing class you want to be in, and 2 liters is max.

What could we do to get bigger than 1915 but still under 2 liters?

A 78 stroke by 90mm bore is 1985ccs, right? 84 by 87 would be 1997, very nearly over-square and probably very torquey for its size. 82 by 88 is 1995. All of these would be in the tradition of the engines made in period, which typically displaced almost, but not quite, the even liter. But no one builds those sizes. Why not?

And if you did, how would those bore/stroke differences affect camshaft and head choices? Would it still do best with over .5 lift? Or would the smaller displacement suggest a milder choice?

Back in the day Chebby made a small block head they called the "powerpack." It was designed for the 283 engines, which had a short (3-inch) stroke and an eighth-inch smaller bore than the 327. The valves in this head were smaller—1.72 for the intake, 1.5 exhaust, as I recall. And it absolutely worked better on the small engines than the more sought after "fuelie" head (2.02/1.6 valves).

Smart hotrodders, if they had to use the short-stroke engines and weren't running 4.11s on an all-out race car, preferred the smaller heads and smaller cams—around .440 lift, which made the 283 ci respectably torquey where the bigger heads and .500 lift cam would render it soggy below the RPM stratosphere.

Has anyone build a 1915 or 2007 with a Web8c and big rockers? How'd it fare?

Lifting the valve over .500" with Panchitos is a waste. The flow is almost no different at .600".

Back in my 2234 thread, I went through some great gyrations to keep lift right at .500" with a long duration cam. Dan Ruddock on TheSamba sells custom Web cams to be used with his beehive springs, which do just that - give a long duration, low lift cam.

It was a trick to find everything, and the first cam I got was ground on the wrong lobe centers, but we eventually got everything we wanted.

Now, if I could just get the motor off the stand and into the car, I could tell you how it works...

Yes I remember that, Stan. The flow numbers didn't pencil out over .5 lift. But how might things change if the engine displacement were reduced to 2.0 liters?

And remind me: what's "long duration" mean in this context, in degrees at .05 inches lift?

My car's Engle W125 specs at .460 lift and 262 degrees (301 nominal) duration. Aircooled.net calls this a pretty radical choice with 1.1:1 rockers, and advises extreme caution at 1.25:1 (where the lift would be .522). But compared to Danny's cam, it's low lift even then! But the Webcam8 has an advertised duration of 272 @ .05.

Is the Engle W125 a comparatively "long duration" cam?

Yes, the 86c has 272 degrees at .050". But the ramps are gentle, which allows the 86b and 86c to not kill the entire valve train even with a1.4 or 1.5 rocker. Those two cams were designed for high lift rockers. I have 45,000 miles on my 86b w/1.5 Pauter roller rockers on it.

I'd wager your Engle W125 has sharper lobes on the cam, which would cause high load and wear on the valve train if used with bigger than a1.25 rocker.

There are engine design programs out there(which I'm not buying). I know Jake used one back in the day to back up virtually his designs in the real world.

I forgot about the lack of more flow in the Panchitos when opened more than 0.5 inches. I'd use a different head(and have) for some bigger valves.

It is amazing what Pat achieved with those though.

Your engine would be perfect with Pat’s new 42x35 heads, Danny. Perfect.

I love this ****, even though I have no plans to build a type one of any kind, so thanks Ed for getting this going.

Danny's point about the steepness of the ramp is spot on. How you open a valve is (to me) more important than how far you lift it, especially when you factor in the volume of the intake system, the velocity of the flow through the heads, and the configuration of the exhaust system. It all works together...or not.

But the quote that really hit home was Stan's "Given that the platform is flawed, the line between "requires care and feeding" and "that wasn't a good idea" is surprisingly fine."

Yeah. I never crossed that line with a type one motor, but I've transgressed it too many times with various other pieces of machinery to be able to call myself intelligent. My learning curve probably looks like the top of a picnic table, or to quote one of my favorite old TV characters, "He's dead, Jim."

Speaking of "Jim" I believe the last word really belongs to El Guapo.

Thanks guys. I get that it's idle (lumpy idle, perhaps?) chat, but I think we can learn something nonetheless.

Regarding ramp rates, this is what I wonder. How can Danny's cam, with .585-inch lift, have a significantly more gentle profile than my .460-inch lift cam, when his effective duration is only 10 degrees more (272 vs 262)? Seems to me that with only slightly (3.8 percent) more duration but very much (27 percent) more lift, the ramps would need to be effectively steeper—accounting for the ratio rockers.

In fact, let's think about what ratio rockers do.

The pushrod end of a 1.5 ratio rocker would move on a much smaller arc than the one on a 1.1. That would seem good for your valve train, keeping the pushrod straighter as regarding the lifter plane.

But in terms of spring pressure I can't see how you gain ground. The valve springs' force by definition are being multiplied back into the lifter face, and thereby into the cam. 1.5 x instead of 1.1x would be 36 percent more force multiplication, wouldn't it?

And would that not negate the effect of having a "gentler" ramp, at least in terms of friction between the cam and the lifter face?

I can only imagine what Ed is thinking when sitting on the couch with his sweetie and watching a nice “Rom-Com”, like “Mama Mia”.

@Gordon Nichols posted:

I can only imagine what Ed is thinking when sitting on the couch with his sweetie and watching a nice “Rom-Com”, like “Mama Mia”.

Too true…..

Ed, the Webcam 86c is 0.585" of lift at the valve, duration of 272 degrees.

My 86b has lift of 0.570", and also shorter duration of 260 degrees.

These lifts are both calculated with a 1.5 rocker.

The 86c is 0.39" at the lobe, the 86b is 0.38". Ed, compare that to the actual lobe lift on cams designed to 1.1 or 1.25 rockers. You'll see that the stock and hot cams aren't that  much greater comparatively(at the cam lobe/lifter).

A stock cam is 0.333" intake and 0.313" at the exhaust. The hot cams really aren't that much more in max lift(60 thousandths or so?).

So we can see there is a real science to cam design and selection, and it is the duration and SHAPE of the ramps that are just as important(if not more) as the peak lift.

P.S.: Youse guys are VERY FUNNY!

Here's a link to Webcam's page.

http://www.webcamshafts.com/pa.../volkswagen/670.html

Click on each cam number to pull up the cam card. And be careful, there are a lot of hybrid cams that Webcam does: different intake and exhaust profiles.

I'm not going to pretend to be a camshaft guru, as camshaft design is 1/3 engineering, 1/3 observed experience, and 1/3 voodoo.

It's said that all the popular Engle "W" series cam profiles are derivations of 1950s and '60s Mopar cams. That would make sense to me, even if it's an apocryphal tale. There are newer profiles, but very few people (Johannes Persson excepted) are pouring huge amounts of time and money into designing a better VW cam. There's still so much to be gained in port and chamber design that cams are sorta' left for later.

Where there is agreement is in ratio-rockers. Modern flat 4 experts all run ratio-rocker cams. They do it because there's less motion in the valve-train (especially in the pushrods, which are the weak link) for any given lift to flex and set up a harmonic. The downside is that the force on the valve-spring pushing on the camshaft is multiplied to a greater extent. We're suffering a lot of "wiped" (flattened) cam lobes of late, but the guys in the know claim it's just cheesy metallurgy, rather than other factors - although keeping the valve-train under control with an FK4X cam (FK43-45, etc. cams have "modern" very steep ramps, which increase the amount of time the valve is at full lift, but which is hard on everything) takes a lot of spring.

Web cams have a reputation of "soft" ramps. JPM (Johannes Persson) has a cam series ("Raptor" Cams) that are 600 bucks with a set of his compatible lifters and a tube of assembly paste which are purported to be really, really nice on the valve-train. When CB lightweight lifters were $70/set, that seemed like a king's ransom, but now that those same lifters are $180, the gap is closing.

I'm not really sure what we're driving at here, other than the engine simulators that a lot of guys use before they ever start building are really, really good - assuming you know what to plug in for real flow and runner volume. There are always going to be variables that make them theoretical, but they have provided a good starting point for good builders all over the world, including Jake, Pat, and the European guys.

There's nothing new under the sun, but we figure out the immutable physical laws that have always been in play through trying (and often failing).

I've heard that story about "Mopar cam grinds" too. Probably here. I decided to believe it then, but now? Why not see if we can find out if it's really true?

First though: Ratio rockers! They are the bomb, aren't they?

I started thumbing through cam grind pages and, sure enough—consensus is the 1.4 and 1.5 rocker kits and the associated cam grinds (FK series from Engle, etc.) are what the cool kids use now. And, as Danny points out, the "big" cams used with those are very similar to stock (or like 110) cams in terms of lift. These cam profiles give much more lift but not so much duration as the previous generation's "hot street" grinds.

So I started looking around at rocker arm designs....

Turns out all the 'murcan V8s from the 1960s used 1.5 to 1.7 ratio rockers. The 194 ci L6 that came originally in my '67 Nova also used a 1.7 rocker ratio as stock.

That seems to be the correct range for a pushrod OHV engine, doesn't it?

So why did Ferdie make our engines with a 1.1:1 rocker ratio?*

And also: why would muscle-era Mopars (of all things) set the standard for hot rod VW camshafts?

I DON'T KNOW.

But I may have found a clue.

That, friends, is an early (as in, 1950s, "Red Ram" era) Chrysler Hemi rocker arm set.

Looks just a bit like

Now, I don't know what the rocker ratio was on those early hemis. I've been researching it...no one says. But just by looking I think it's closer to 1.5:1 than 1:1.

So maybe not.

But...maybe?

Because the other thing the early Hemi engines shared with the Type 1 was low compression ratios. That was a deliberate decision by Chrysler's engine boss,  who thought GM and other manufacturers were getting cheeky with their high compression engines and concomitant dependence on high octane fuel.

"He reasoned that relying on external factors like high-octane gas (the 'stimulants') would spell disaster if fuel shortages ever materialized and only low octane was available—which is what happened in the early 1970s with OPEC," according to the linked article, which also covers some of the Hemi's (and Chrysler's) post-war history. Turns out the hemi head shape was not that important after all, but the valve arrangement (as with the Four Cam engines) was.

The '50s and '60s hot cam grinds all showcased increased duration more than lift, and recommended higher compression ratios too. It's only that past 25-30 years that higher lift/less duration came into fashion. And by then stock engine compression ratios were already going up into the double digits—probably owing mainly to modern computerized spark timing and fuel delivery, and ubiquitous knock sensors.

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*Could it have been something to do with the designed length of the aluminum push rods? The expected strength of them circa 1940?

Many reasons come to mind for pushrod material choice.

The cars were cheap and not expected to last too long.

Aluminum was light, quiet, and perfectly adequate for the intended rpm range.

But, most importantly, aluminum expands at a VERY similar rate to magnesium. So, valve clearances remained pretty stable throughout the temperature range of the engine.

And yeah, I noticed that 1.5 and up rockers were used on big old American V8s. But the pushrods were almost invariably steel, and none of them saw much more than 6000rpm, unless they were racing.

@edsnova posted:

... So why did Ferdie make our engines with a 1.1:1 rocker ratio?*

@Stan Galat posted:

... we figure out the immutable physical laws that have always been in play through trying (and often failing).

I've spent a lifetime studying the work of people smarter, wiser, or more gifted than myself - because I've been given just enough spin on the ball to know what a mess I can make of things left to my own devices.

The thing is - no matter how good somebody is, a thing almost never hatches perfectly formed on the first run at it. I make fun of the Sainted German Engineers, not because I think they were nitwits, but because so many guys worship their work - as if it were scripture, with every jot and tittle emanating from the hand of the prophets as they were driven along by the Spirit of God Almighty. It's silly.

They were good at what they did, but they (like everybody else) almost never got a thing perfectly right on the first go-around. They made compromises based on the materials they had at their disposal, the design parameters, and most importantly - the things they knew at the time.

Maybe they used 1.1 ratio rockers because the rocker shaft arrangement and push-rods couldn't handle the force multiplication of something greater, and they didn't know how to make a better one. 1.1 was perfectly adequate for the low-revving, lightweight, <40 hp application. Seriously - your lawnmower is approaching that level of power, and probably runs more reliably with a lot less maintenance. It's not because the engineers at Briggs and Stratton are brainiacs (although I'm sure they're fine engineers) it's because they're also building on 150 years of accumulated knowledge.

The Sainted German Engineers of the 1930s were not. They were mostly making it up as they went along. Ditto the hotrodders of the 1950s and 60s - they were supersmart people, but they were just doing what I do - which is look at what's working for other people, think about what's happening, and try to do it the same way or better. It's important to remember that there wasn't nearly as much accumulated knowledge when they were doing it.

The laws of nature haven't changed, it's our ability to understand them that is incomplete. There's a lot going on inside an engine, and while we've arrived at some standard approaches, there's still a lot to learn... but there's less to learn than there was 50- 90 years ago.

Approaching the work of people long gone from that angle seems better than looking back on what they did as if it is a lost secret.

VW used 1:1 rockers on the 40hp and earlier engines, they changed to 1.1:1 ratio rockers on the 1300.  

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By 1932, our good Dr. Ferdinand was already a respected designer of racing cars, so knew from experience what was schnell, and what was not.

But the doodlebug was definitely not a racing car. It needed to be sturdy and reliable, but, above all else, able to be banged out as cheaply as possible. I'm guessing cost cutting had more to do with design decisions than anything else.

And then, the thing had to run on what pump gas was available in the fatherland at the time, which likely had an octane rating about the same as chicken soup.

I think Stan is probably right about not seeking brilliant design revelations in the length of VW rocker arms.

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@Sacto Mitch posted:

.By 1932, our good Dr. Ferdinand was already a respected designer of racing cars, so knew from experience what was schnell, and what was not.

Nothing interests me quite as much as visiting an aviation or racing museum, because the machines there represent the actual state of the art in their respective period (aviation especially).

I've been to enough of both to know that while Herr Doktor was a brilliant man, and the engineers of his time were smart in a way I can't imagine - the state of the racing art in his time wasn't nearly as far along as the average economy-car engine in 2023.

It's just a fact. I'd much rather look to what is working for people right now than what Gene Berg or Bob Hoover or Ferry Porsche did before there was a mountain of data to build upon.

Stan:

Next time you and Jeanie visit, we will go to the Air Force Armament Museum at Eglin Joint Services Base.

It is really interesting. Lots of great planes, weaponry and displays of engineering.

After following along on this, I thought I would post what the specs are on the Engle 120 cam that I'm running, so here you go (Pretty cool diagram, too):

Camshaft Spec Sheet

@Panhandle Bob posted:

Stan:

Next time you and Jeanie visit, we will go to the Air Force Armament Museum at Eglin Joint Services Base.

It is really interesting. Lots of great planes, weaponry and displays of engineering.

I’ve been to the National Naval Aviation Museum in Pensacola.

I went with my wife and my (then) 17-year-old daughter. They allotted me 2 -1/2 hours. I barely made it out of the biplanes. The advancements were breathtakingly rapid as they built on what they’d learned.

@Stan Galat, I have been to several aviation museums. I too think the speed of advancement in the early days was just breathtaking.

Here in Michigan, we have the Air Zoo. I went for a ride in a Ford Tri-Motor there.

Within an hour's drive from me is the Canadian Warplane Heritage Museum.

https://www.warplane.com/

They have one of the remaining flying WWII Lancasters, and I was lucky enough to win a flight in it a couple of years ago.  They also just got a Spitfire that they are planning on restoring.

We try to make it there at least once a year.

My son and his family just got back from a whirl-wind trip to Washington DC and one of their regular stops in the area is at the National Air and Space Museum out by one of the airports.  The two grandsons usually rave about the place for a week or so after returning home.