CC'ing your heads (L O N G!)

CC'ing, CR'ing and BS'ing
Most folks arrive at this point not because they are building an engine but because they are repairing one. Doing a valve job on a VW engine alters the
chamber volume. Or they've dropped a valve and have had to replace one of the heads. Replacement or repair of a head alters the chamber volume and chamber volume is a factor in the compression-ratio equation. Before they can re-assemble the engine they have to measure the chamber volume and re-compute the CR to ensure the repair work has not upset the compression ratio.
Measuring chamber volume is easy to do and the procedure is all the real service manuals for the VW engine. But just to keep all the information in one place, I'll give you a quick sketch of the procedure.
Using the catheter-type syringe and a sealing disk similar to those shown in the photos, you should be able to measure the volume of a Volkswagen combustion chamber to within 2cc. That is, if you measure it a multiple number of times your results should not vary from the AVERAGE result by more than plus or minus 1cc. (As a general rule, always measure each chamber at least three times.)
Herez how: Install a spark plug in the head and torque to spec. If the valves are not perfectly fluid-tight, pop them out and put a light smear of Vaseline on their sealing surfaces. Level the head in both directions then smear a light coat of Vaseline around the periphery of the sealing disk and drop it into the chamber. If the sealing disk is 3/8" or thicker it will be heavy enough to stay in place by itself (the specific gravity of cast acrylic sheet is only 1.19). For thinner sealing disks you'll need to hold them in place while filling the chamber or add a few ounces of weight to their edges.
The disk(s) doesn't have to be perfectly round. You can saw the thing out with a jig saw, smooth the edge with a file and you've kept it to within +/- sixty thou or so, it will work perfectly well. Nor do you need five holes in the disk as shown in the factory workshop manual; you can do a quick check with just one.
Using a suitable fluid, fill the chamber and the hole through the sealing disk. Subtract the volume of the hole from the total. Do both chambers. For OHV engines I think you'll find ‘wetter' water does a better job than the traditional kerosene. This is because you need to measure the chamber several times and average the result and that means you have to remove ALL of the fluid from the chamber. With a flat-head engine it's pretty easy to simply wipe the chamber dry but with an OHV the kerosene tends to cling to all the nooks & crannies. So use water with a drop of wetting agent as your fluid. When it comes time to dry the chamber, simply dump it out, slosh it with a bit of alcohol then BLOW it dry. Alcohol is hygroscopic - - it will mix with any remaining water and once mixed with alcohol it takes only a modest blast of air to dry even the deep recess around the spark plug's insulator.
A quick check using the syringe shown in the photos will allow you to determine the volume of your combustion chambers to within 2cc (i.e., plus or minus 1cc). To compute your compression ratio use the LARGEST volume you measured as the factor in the CR equation.
That's it. If you're a shade-tree mechanic you're all done. Good luck in the contest.
CC'ing Tools & Equipment
WHY ARE WE DOING THIS?
Truth is, some of you aren't. Although this article was written to explain how to improve your engine's efficiency by adjusting it's volumetric balance, many builders are interested only in determining their compression ratio. If that's all you're here for, drop down to MEASURING CHAMBER VOLUME.
By applying modern-day standards of balancing, of both mass and volume, you can pick up as many as ten free horsepower from a bone stock VW engine. And I mean ‘free' in the sense that it will use the same amount of gas. That seeming impossibility reflects the fact the engine must first overcome any internal imbalance before it can deliver any usable power. That means an imbalance generating a loss of five horsepower costs an additional five horsepower to balance the books, resulting in a net loss of ten horsepower. This is a key factor in the importance of balancing and one most people overlook. That is, for each imbalance you eliminate you will gain approximately TWICE that amount of improvement.
Of even more importance to builders of flying Volkswagens is the fact that a properly balanced engine is more durable and the reduction in wear is even more pronounced than the improvement in fuel efficiency. That's because most of the internal imbalances appeared in the form of friction and heat, which could only be overcome by generating MORE friction and heat. The bottom line is that a 3hp imbalance could cost you up to four times that in additional wear. Eliminate the imbalances and the engine's wear-factor takes a dramatic drop.
The benefits of mass-balancing became self-evident as the normal operating speed of internal combustion engines was increased but the role of volumetric balance was not fully appreciated until computers came along. Once they had a super-computer to play with automotive engineers discovered that a lot of what we thought we knew about the process of combustion was not entirely correct, that there were transient phenomenons due to volumetric imbalances that we'd attributed to other causes. This is one of those non-intuitive kinds of things, not easily explained without a bit of background but the basic reason has to do with the process of combustion and the fact those seemingly insignificant differences in volume appear on both sides of the compression ratio equation. Turns out, relatively small variations in volumetric balance can produce some relatively large losses of power. Since that time they've taken exquisite pains to reduce those imbalances. How this is accomplished in a mass-production environment is quite interesting (at least, to me :-) but the bottom line is that we can take advantage of what they've learned by simply paying more attention to the volumetric balance of the engines we build.
Thanks to computerized equipment a modern balance shop can do mass-balancing to a fraction of a gram at a very reasonable price. But matching the volume of a pair of heads (i.e., four chambers) to a tenth of a cubic centimeter remains more art than science. In the racing world it isn't uncommon to pay a thousand dollars for a pair of full-trick heads, their volumes accurate to 0.1cc across all four chambers. The cost isn't in the tooling; it doesn't take a lot of tools for head-work. The money goes to buy the head-man's time. That fact is in our favor because time is about the only resource of which lo-buck homebuilders have a surplus. By acquiring a few tools and devoting a bit of time to your heads, you can bootstrap yourself into a better engine than you can afford to buy.
At this point a majority of non-mechanic home-builders are sitting there with a large black question-mark floating in the air over their heads. If adjusting chamber volume is more art than science, how can they hope to tackle the job themselves?
The answer is so simple it will make you smile. ANYTHING you do to reduce the magnitude of the existing imbalance will improve the efficiency and durability of your engine. The fact the pro's regularly balance to a tenth of a cubic centimeter is like running the four minute mile. But we're just a bunch of week-end joggers so let's not even think about that degree of precision. At least, for now. Instead, let's look at the basic problem.
You have four chambers. You measure them (the procedure is outlined below) and come up with four values, probably accurate to within half a cc or so. Using real numbers now... two heads measured 56.5, 58, 58, and 60cc. Rather than trying to turn you into a head-flow guru capable of achieving 0.1cc accuracy on a repeatable basis the question becomes: "Can we reduce that 3.5cc spread to something smaller?"
The answer is a decided ‘Yes!' And it really isn't all that difficult because you only have to work on THREE of the chambers. That is, you can't make a chamber any SMALLER so the largest chamber becomes your target-size. So relax. You CAN do this. And you'll end up with a better engine because of it.
Then comes the question, how much metal are we actually talking about? Just what the hell IS a ‘cubic centimeter'? The answer to both: Not much.
If you've been following the Practice Wing project you should have some high-density urethane foam on hand. Print out the ONE_CC drawing, glue it to a piece of foam then use a razor blade to make a cube the size of the printed square. That is, a cube 0.3937" on a side. No foam? Then make the cube out of wood. Or plastic. Or tool steel (if you can). The goal is to give you a tangible reference to the volume of a cubic centimeter.
Hold a cubic centimeter in your hand and three things are immediately apparent: Firstly, it isn't very large. Just a tad over 3/8" on a side. Secondly, you can appreciate the heroics it takes to achieve repeatable tenth-cc accuracy. And finally, you can see why a lot of people consider such imbalances to be insignificant. To the uninitiated, something that small has to be unimportant; something they can ignore.
Got some sixteenth-inch ply? Okay, howz about some poster board a sixteenth of an inch thick. Or a piece of .063 aluminum. Three-eighths wide, six inches long, you're looking at about one cc. Now go back and look at what we're trying to do. To balance the 56.5cc chamber we need to remove three and a half cc's of material. Just unshrouding the valves is usually good for that volume.
So how do we do all that? I'll get into that in a minute but it all begins by measuring the volume of your combustion chambers.
MEASURING CHAMBER VOLUME
If you've never cc'd your chambers, relax; it isn't difficult nor do you need a lot of equipment.
My first exposure to cc'ing heads was in the mid-1950's. I bolted a piece of plex to the freshly milled head of a Ford V-8, leveled the thing up with wedges and used a turkey baster to fill each chamber with kerosene. After doing both heads I plugged the SMALLEST volume into the compression-ratio equation and came up with a CR of about 11:1, assuming I used a sixty-thou gasket. Life was good, assuming I could swipe enough avgas for a couple of runs through the lights :-)
Determining the volume of the combustion chambers is a chore common to all engines and the basic procedure is the same for all. The procedure requires:
1. Some means of holding the head level.
2. Some means of sealing the space to be measured.
3. A method of accurately measuring the amount of fluid needed to fill the chamber.
Working with nothing more than a 1/4" drill motor and a couple of carbon steel rotary files, cleaning up the marks with a strip of sandpaper spiraled around the split end of a quarter-inch dowel, you can expect to produce a cc-job accurate to about 0.5cc across all four heads. Indeed, the usual problem when a novice does his first set of heads is going too far, opening up the smaller jugs to a volume larger than the target-jug. Which means they have to take a bit out of the big chamber, which usually leads the them chasing the volume back & forth until they get sick of it.
SAME PRINCIPLE, DIFFERENT PROCEDURE
The secret to hitting your chamber volume dead-on is exactly the same as for hand-cutting a piece of aluminum to a precise dimension in that you don't shoot for the exact dimension. You always give yourself a clean-up allowance. Cutting aluminum by hand you snip or saw the thing about forty-thou over-size then dress the edge with a file. You do much the same when cc'ing your chambers in that you use the rotary files to get close to the finished size then begin smoothing things up with abrasives, checking the volume periodically.
I mention this now because the next subject has to do with the precision of your cc'ing job and the fact balancing your chambers to a fraction of a cc might take you a couple of weeks (!) if you've never done it before, whereas balancing them to 1cc (across all four) should take only a few hours. If you don't want to spend the time then there's no need to spend the money for an accurate liquid dispenser, such as the one shown in the photos, which is graduated to 0.1cc. Turkey baster or the big syringe, you can work down to 1.0cc with fair accuracy. And there's a BIG difference in price between a surplus syringe and a certified-accurate, lab-grade burette.
All engines get their chambers cc'd, not just Volkswagens. The cc'ing of combustion chambers is illustrated and talked about in the various manuals on engine building. The three key elements mentioned above reflect the basic core knowledge for any cc'ing job. Then comes a host of details; the How-To stuff, most of which is engine-specific but some of the common factors address the accuracy of the finished job, the degree of precision, how long it takes and various convenience factors. As with most other aspects of proper engine fabrication, cc'ing your heads calls for a keen attention to detail. Most of the time.
The point is that you really don't need much to do a quick check.
Lots of after-market retailers will sell you a ‘cc kit.' It usually consists of a plastic syringe like the one shown in the pictures (see the Fly5kfiles archive) plus a plastic disk with a hole in the middle.
What's it cost? Hard to believe but some outfits want as much as thirty bucks for a cc kit.
See the syringe in the photos? It comes from a veterinary supply house. New, quantity one, you're looking at three or four dollars. But syringes have a certain shelf life and once they're past it, the supply house often flogs the stuff off as surplus, out-dated or whatever. Buy them a dozen at a time, the syringe shown cost about half a dollar.
The plastic sealing disk is any sort of flat plastic, eighth of an inch thick or more. Doesn't have to be clear. The sealing disks I use for 77mm jugs are made from a hunk of red Plexiglas I dug out of the scrap box at a plastics retailer. In a pinch I've even cast my own using polyester resin on a sheet of waxed glass. It only has to be flat on one side and just clear enough so you can chase the bubbles. Chasing the bubbles is one of those little details no one mentions :-) The bitter truth is that some bubbles don't like to be chased and you can spend the best years of your life trying to coax the thing over to the hole.
The sealing disk in the typical kit has just a single hole in the middle. Cheap, easy to make and so forth. But harder to use than one with more holes. More holes, you don't have to chase the bubbles so far but more importantly, with more holes there's a better chance you'll be working with a truly LEVEL head. And that's worth mentioning because a lot of after-market heads, especially rebuilts, the sealing surface is NOT parallel to the valve gallery gasket rail, which is what you use to sit the head on.
So you sit the head on the gasket rail (after taken the studs & valve stems into account) and use your machinist's level or framing level or whatever on the chamber-side of the head to use wedges and so forth to get everything perfectly level, end-to-end and fore & aft.
That's no guarantee the CHAMBER is level. But if your sealing disk has a pattern of holes as shown in the drawing (and in the VW factory workshop manual), as the chamber fills the level of the fluid in the various holes tells you if the chamber is level.
You subtract the volume of the holes, by the way. Figure it out ahead of time, scribe it right onto the sealing disk. You can use the same equation as for V1, just substitute hole diameter for bore and the thickness of the plastic for stroke. Then multiply that by however many holes you have and be sure to always fill the hole to precisely the same level.
Buy a cc kit, it usually comes with only one disk for each size of cylinder. Indeed, some outfits only sell you ONE disk, period, screwing you to the cash register if you want two disks or a set of a different size. Which is another example of how VW after-market retailers screw the kiddies, because to do the job properly you really should do both chambers at the same time... and that means two disks of each size.
Making disks is pretty simple, assuming you understand plastic. Drills for use with plastic looks like a needle :-) We usta call them ‘canopy bits' or ‘Plex bits.' Included angle of something like 30 degrees. If you don't have a set of bits for plastic and don't know how to sharpen a drill bit, you'll have to use a hand-drill. Even then, you're liable to crack it when the bit breaks through the other side. That's when it grabs the flutes. Plastic bit, you needle a pilot hole then flip it over, finish it from the other side. Slow speed, always. Kerosene makes a good lubricant for thicker stock.
Although the sealing disk drawing I've posted shows dimensions to thousandths of an inch that's just the math. You can cut one out with a jig saw and it'll work just fine. That's because the sealing LIP inside the combustion chamber is at least a tenth of an inch wide. So long as the disk is close to a true circle and makes good contact with that lip, it will work okay. (Too big? Then sand the edge.)
Once you understand the purpose of the sealing disk you'll see them all around you, just waiting to be cut out. See that translucent plastic over the waterproof light in the bathroom? That'll work. You can still see the bubble. Got some curvy scraps from an a blown canopy? That'll work. Just put it on a heavy plate of polished aluminum, pop it in the oven set at about 300 and let it flow out flat.
Want to keep your sealing disks nice & pretty? Got some old 5-1/4" floppy disks? Cut one open, throw away the disk, store your sealing disks in the sleeve.
To make your chamber water-tight you smear a little Vaseline on the valve seats and a light wipe around the outer-most edge of the plastic disk. Then you fill the syringe to a precise level and use it to fill the chamber. Subtract what's left in the syringe from whatever you started with, then subtract the volume of the hole(s) in the plate and that's the volume of your combustion chamber, accurate to however accurate YOU are and as precise as the divisions on your syringe. - - - - - - - - - - - - - - -
On the other hand... there's lots of lab equipment scaled to 0.1cc increments but most of it lacks the volume to fill a chamber. VW combustion chamber volume may be as small as 40cc or as large as 80cc, depending the size of your valves and the displacement of the engine. A burette large enough to hold one chamber's-worth of juice AND accurately marked to 0.1cc precision, you're talking about an expensive piece of goods. The high price of the Good Stuff comes as a shock to guys building just a single engine, often causing them to settle for half a loaf, using a turkey baster of whatever.
So use a marble or two. And a smaller but more precisely marked burette.
Got a marble? There's a free one in every can of rattle-can paint. (That's the rattle :-) Or you can buy a bag of them at the dime store. Or use steel ball bearings (but remember they rust). I like ball bearings because of their uniformity. Marbles vary by quite a bit.
So what's the volume of your marble? Half fill your burette, bring the meniscus to the line, make a note, then drop your marble into the burette. Make another note then do the match. (You may shout ‘Eureka!' if you wish :-)
By adding objects of known volume to your combustion chamber you can use a smaller dispenser marked to 0.1cc graduations. Just be sure to keep the numbers straight. (KEEP GOOD NOTES!).
When trying to achieve the smallest possible difference across all four jugs, statistics are your friend. Make all of your measurements a number of times and then average them. This helps to reduce the human error, a factor that can be deadly for the first-timer. Without experience you can't appreciate the significance of seemingly minor differences. Do everything several times, throw out the high and the low then averaging the remainder tends to reduce any errors of observation.
Work with good light. Don't be shy about using a reading glass to inspect the meniscus in the sealing plate holes and your burette. When taking a series of measures on the same chamber(s) always be sure to start with it perfectly DRY. That means you'll need an air blast to blow out the spark plug (which should be torqued to spec on a new washer).
Once the sealing disk is in place, it don't wanna leave :-) Use a dental tool or bend a tiny hook on the end of a piece of wire to lift it out using one of the holes. Pour the water out of the chambers, wipe them down with a clean towel, blow the plug dry. Before blowing them out I swap the chambers with lacquer thinner or MEK to remove any oily residue that might prevent the fluid from fully wetting the surface.
Traditionally, the liquid used for cc'ing heads was kerosene. (I donno... it just was.) Working with VW's I've heard guys advocate the use of everything from anti-freeze to ATF and big dummy that I am, I tried them all.
Hell of a mess.
Light oil of any kind is a contaminant in the shop and can be a fire hazard. And glycol, Prestone or what-have-you is poison. In the mid-70's I started using ‘wetter' water for cc'ing and found it gave more consistent results and a lot less mess. How do you make water wetter? Originally, I added a couple drops of ‘Photo Flow,' darkroom stuff that prevents water spots on your negatives. But for cc'ing heads, a couple of drops of liquid detergent per gallon of water has about the same effect. A drop or two of food coloring will make it easier to see in the burette. Try to work in a room-temperature environment. The temperature of your measuring fluid and the heads should ALWAYS be the same. (Keep the liquid in the shop with the heads. You'll need to do rough spot-checks as the works progresses. I'll have more to say about that in a minute.)
I normally use a burette similar to the one in the photos. You'll notice that it's attached to a standard that bolts to the base, which is a plywood box filled with concrete. To attach the burette to the standard, fancy name for a scrap of plywood, I twisted some welding rod around a bolt a little smaller in diameter than the burette so the resulting hair-pin-looking piece would grip the burette. To fasten it to the standard I drilled a pair of holes, poked the legs of the hair pins through the holes, bent them over and covered the bent ends with a slather of Bondo. (You can see all this in the pictures.)
The base is heavy to prevent it from tipping over and breaking the burette. It is leveled with shims or screws then the burette is OVER-filled using a pitcher and funnel. To dispense the liquid I use a length of surgical rubber tubing (drug stores carry it) fitted with the glass tip from an eye-dropper. Flow is controlled by a clamp on the rubber hose. Once the burette is over-filled I bring it to the line by releasing the clamp and returning the fluid to the pitcher or bucket. To fill the chamber I bring the fluid level to the base of the sealing disk then chase out any bubbles by tapping on the disk with my fingernail or the handle of a dental tool. Once all the bubbles are accounted for I fill the central hole a drop at a time until all of the holes are at precisely the same. Then I read the burette, hunkering up or down to eliminate any parallax.
Measuring a chamber takes me less time than it took you to read the paragraph above. Using two disks allows me to do both chambers with one set-up.
Then I do it over again.
To determine the finished volume, as when I'm down to the point of making fractional cc adjustments, I measure each chamber as many times as I think I have to. Sometimes I'll get three identical measurements in a row on both chambers. And sometimes I'll do it half a dozen times and get a different measurement each time, usually when I'm tired or whatever. (People wonder why I don't answer the phone or throw rocks at them when they arrive unannounced. Now you know :-)
That's how I do it when I'm balancing the volume of the heads, trying to achieve 1cc or better across all four. When I'm just WORKING on the heads, I generally use a syringe. It's only accurate to 2cc but it's a lot faster and when you are first opening up the heads 2cc accuracy is more than enough.
- - - - - - - - - - - - - - - - - - - - - - - - - - -
When building a big-bore engine, cc'ing your heads begins long before you get around to calculating your compression ratio. In fact, it starts when you first acquire the heads. If they're new, with valves already installed, just install a spark plug, grease them up and do a rough measure of volume. Otherwise, rough in the valves then install a plug. Level them up, select the appropriate sealing disk (if you haven't opened them up they'll be some other size) and use a baster or syringe to get some idea of their as-cast volume. It's handy to write that volume directly onto the head using a crayon or wax pencil. The heads should already have been documented and assigned a work number and a documentation package (sounds complicated; actually, each head is just a page in a notebook.) A lot of folks think that's overkill for just one engine but during the course of the work you must have some means of identifying the chambers and even one engine has four of those suckers in two identical heads. And if it's a really GOOD engine, you'll make up a set of spare heads, identical to the first set. Having a spare set of heads on-hand allows you to swap heads when necessary and do the valve work at your convenience.
When you open up your heads for bigger jugs you are trying compress the swept volume of the larger jug into the original compression space. There's no doubt the compression ratio will go UP. The big question, is how much? If the only thing that changed was the swept volume and the deck clearance was kept the same, going from 1600cc to 1834 is going to raise your CR by about one point. But that's the myth that leads to blown engines because NOTHING remains unchanged. When you open up the heads even the slightest skim cut will reduce the chamber volume. Another part of the myth is that most guys don't know what their original compression ratio was to begin with. Later model engines ran 7.5 or 7.7 (the Export crate engine from the Puebla plant is 7.7) depending on the heads but if it's been overhauled a few times you could be using heads that have been flycut. Bottom line: It isn't uncommon to see 1834's with a CR of 9:1 or more.
Opening up your heads for bigger jugs offers the opportunity to unshround the valves. Unshrouding the valves results in a profound increase in flow-rate for the same amount of lift. The procedure is covered in Bill Fisher's "How to Hot-rod Volkswagen Engines" but I'll try to insert a couple of photos to show you what I'm talking about.
To unshroud your valves you have to remove metal from the chamber. Any time you remove metal from the chamber you need to cc the chambers to make sure they all end up the same size. This is normally done several times as the work progresses.
Okay, so you're using a syringe and a sealing plate with one hole and you've never done it before and you think my talk about attention to detail is all bullshit so you squirt them just once and come up four measurements ranging from 55cc to 60cc. Now what do you do.
What you do is go back and do it again :-)
When you're satisfied that your measurements are as accurate as they're going to get, the next step is to decide on a strategy for INCREASING the volume of the small chambers to bring them closer to the volume of the largest chamber. By this time you should have some idea as to the physical size of one cubic centimeter and your measurements have told you how much each of the three smallest chambers must be opened up to match the volume of the largest. The tricky bit is WHERE to remove the metal from.
Basic starting point is unshroud the valves using rotary files. Then do a quick syringe-check. You want to STOP with the filing when you get to with 1 cc of your goal.
If unshrouding the valves does not give you enough volume then you begin ‘laying-down' the edge of the combustion chamber. Here again, start with your rotary files. Try to visualize the amount of metal you want to remove. Remove NEARLY that amount then CHECK IT. When you get to within 1cc, stop using rotary files and shift to using abrasive rolls.
The principle behind smoothing things with abrasives is to simply remove the tool marks from previous steps. That means using a tool (or abrasive) that will leave SMALLER marks. So you start with coarse sandpaper and when you've removed all of the marks of the rotary files you'll be left with the marks made by the sandpaper. So you shift to a FINER grade of sandpaper and do it all over again. I generally use 80, 120 & 220. After 220 I shift to felt hobs and polishing compound.
A key point here is that I never try to hit the target volume dead-on, I only try to get CLOSE to it and always on the high side. A second point is the need to periodically check the chamber volume as the work progresses... and to check it with an increasing degree of accuracy. That is, a syringe or turkey ba
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..............Thanks for sharing your knowledge with us Bob. I've got a new pair of 'level 3' heads on order from Aircooled.Net for my Berg 1679. The ones that the PO installed are the semi-hemi style and they run really HOT! I'm going to get the items that you've suggested for CC'ing these new heads and get to work when they arrive. When I get them done, I'll post a link to some pics.
...........If I can start blowing away those pesky V-TEC Civics, I'll be happy.............lol
Best regards
Tim Rogers
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You're kidding, right?
Come on, tell me yer kidding... or tell me where you live so I can bet on the other guy. Because you're comparing 1930's oranges to 21st century apples.
You got any idea what 'V-TEC' stands for? It means the engine employs variable valve time and electronic control. That allows you to pull as much as 200 horsepower out a two-liter engine. And do it year after year after year after year...
You want lotsa oom-pah from an air cooled engine? Then you gotta design one with LOTS of cooling fin area -- about THREE TIMES the fin area of the VW head. (Now imagine the SIZE of that sucker!) Then you gotta give it some valves that will last.
Ever been inside a Porsche engine? Ever wonder why the exhaust valves have such fat stems? Or why they have their own rocker shafts?
You can produce as much as 300hp from a normally aspirated engine based on VW components. For maybe ten seconds. If you're lucky you may even be able to do it twice. Then it's back to the pits to plug in another ten thousand dollar engine, because that's about what a good one costs. But like most gasoline-fueled engines, the VW is only about 25% efficient. So if you manage to couple 300hp to the asphalt it means you did so by producing 1200 horsepower's-worth of heat.
Want to guess where that other 900hp of heat goes? If the heads have fins the size of car doors, some of it will get coupled to the atmosphere and the thing may survive. But a lot of that heat appears in the exhaust valves, which tries to get rid of it by conduction from the stem to the guide and THEN into the head... where it better find about a dozen fins the size of a car door getting blasted with about 32 THOUSAND cubic feet of air per SECOND because that's about it needs to keep the cast aluminum from exceeding it fragmiable point(*)
But none of that happens.
The heat soaks into the heads, the valves warp, the stems gall the guides and you swap engines for the next run. Reality 101.
VTEC engine is LIQUID COOLED. You wanna pump 200 horses out of a water cooled engine the size of a shoe box, all you gotta do is increase the coolant's rate of flow... use a bigger pump or spin the one you got a little faster... and feed it into a bigger radiator... or add acouple of blowers to the one you got. (Compare the density of air to water. Assuming equal thermal transfer [which isn't correct but work with me here...] water is about 800(!) times better as a coolant than air.)
Ferdinand didn't go with air cooling because it meant there was nothing to boil, he did so because there was nothing to FREEZE. (Berlin is as far north as Winnipeg.) Truth is, air cooled engines don't like heat. Or hot weather. They're niche engines, happiest when pumping out a very modest amount of power on a relatively cool day. (
See all them dyno pulls in the magazine? Ever read the fine print? About how the output is 'adjusted for Standard Day conditions' and so on?
'Standard Day' means the barometric pressure is 29.92 and the temperature is 59.9 degrees on the Fahrenheit scale. And when it isn't, and you're doing dyno pulls, the air density and ambient temp are 'adjusted.' Which is where the magazines get all those bullshit dyno figures from :-)
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Lemme offer you a couple of tips. The first one is to never play the other man's game. Right now you're guilty of doing that twice. Once, by failing to understand the realities of trying to upgrade an antique air cooled engine to equal the performance of a modern, fuel-injected, water cooled engine having variable valve timing. And a second time because you've let someone convince you that you CAN, simply by paying them lotsa money for trick parts.
The second tip is related to the first in that, if you wanna wax an idiot in a Honda, simply convince him to play YOUR game.
Ever played bumper tag? All you gotta do is pop the balloon taped to the other guys rear bumper within a given number of minutes or miles, after so many seconds for a head-start and with a third party holding the pinks.
All set? Then fire up your bug, tighten your belts, give the dummy an evil grin... and drive off the road. Cross-country. Downhill, if you can arrange it.
Stock bug has a very nice weight distribution and superb traction. If you know how to drive, it does about as well off-pavement as on, other than going a little slower.
Honda can't even drive over a curb without trashing itself. I understand they got rid of that dinka wish-bone front suspension but no way is the thing an off-road vehicle.
A VW is. In fact, if your bug is a '68 or older it's little more than a military vehicle in civilian dress.
Stop falling for the automotive equivalent of Three-Card Monte and get the other guy to play YOUR game for a change.
-Bob Hoover
(*) fragmiable isn't a real word, I just made it up. The real word for something that breaks apart easily is 'frangible' but when applied to overheated VW heads it lacks the dramatic quality of a fragmentation grenade going off in your engine, which is closer to what really happens when you overheat a VW.
Unlike iron which remains malleable at elevated temperatures -- and retains much of its strength -- cast aluminum becomes frangible at temperatures above 450 F. Subject it to stress, it breaks apart like a sugar cube.
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snipped-for-privacy@aol.com (Veeduber) wrote:

Okay, not "lotsa oomp-pah", but a modest 150hp from a propelry build 2200cc T1? I find it interesting that you presume the iron cylinders. How about machined aluminum cylinders machined generous fins and nickel silicon carbide plated bores and not-so-giant finned heads? I truly think you would be challenged to get them hot enough to cause heat damage under normal and even spirited driving, even in the high-plains desert.
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snipped-for-privacy@xyzzy.stafford.net (jjs) wrote:

Boy did I mess up that post. Been up all night sleepless. Sorry.
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Hondas. If for no other reason than because one of them probably saved my kid's life when she was a really stupid seventeen year old who needed a second chance.

VW
to do

dollar
manage
...............I just want 90+ hp for a minute or two, occassionally. I pay close attention to oil & head temps and always back off when things are getting too hot.

other
failing to

to
having
convince
..................I just want to make it from one stop light to the next before a fwd small sedan with variable valve timing can find enough traction and useable power to blow by me. I'm about 30+ years older than most of those guys and in their more sophisticated cars and this is about all the gratification that I can handle these days. A 1700 lb. bug with superior traction and almost 100 hp is capable of that. Like I said, out on the open road, I'm a lot more sensible about how hard I drive this antique relic from the past. With the mild climate here in upstate NY, I can usually sustain 75 and sometimes even 80 mph without excessive heat build up. When it's a hot day(85?), I typically end up staying at 60 mph. My rule of thumb is to never let the head temp exceed 400 deg or the oil temp to exceed 250 deg. After almost 17k miles since it was built, this Berg engine is still running flawlessly with virtually no oil consumption. The high head temps are hopefully caused by the semi-hemi cut heads that are coming off pretty soon. I'm really sold on these machine-in 88mm cylinders. This engine has great compression and is more difficult to pull through a compression stroke by hand during valve adjustments than any type1 that I've seen during the past 30 years.
............Sorry about snipping more than half of your post Bob, but it is archived in a folder that I keep that has almost 90 posts from you to RAMVA beginning when I bought this pc last August.
Tim Rogers
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wrote:

...hmmm...17.....+ 2.... (takes off shoes to help with addition....)....that makes her offically legal in all 50 states =-)))))
...Gareth
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.............Now that you're a naturalized southerner, maybe you should be looking into how many cousins are in your family tree.
<G>
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wrote:

30+ years older than them and still street racing? That doesn't sound very responsible to me.
--
Less drivel, more Dremel.
Always carry a flagon of whiskey in case of snakebite,
  Click to see the full signature.
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*SPUTTER*!!! The Shag is talking about responsibility! This is gonna be good! Okay, Shaggie, pull up a quarter roast, a six-pack and pint of Jack and tell us. We are all ears, sittin at your feet like lonely doggies before The Buddah (Boodah, BooDay, whatever.)
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On Sat, 29 May 2004 18:10:16 -0500, snipped-for-privacy@xyzzy.stafford.net (jjs) ran around screaming and yelling:

so you *know* shaggie well enough to question his ability to be responsible?....the man has several children and a wife and provides for them pretty well...i'd say he's pretty responsible....he has worked hard to make a career for himself so he can do these things, that too would lead me to believe him to be "responsible"....tell us "O'great John" what is it about him that makes you believe he isn't "responsible"? Is it that he isn't afraid to laugh at himself? Is it because he can have a good time? Is it because he isn't afraid to be himself? tell us John, what is it that bothers you so much about a person that you don't even know? Then we can talk about you and your massive mood swings if you want.. JT
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Way too easy. Hook, line and sinker.
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On Sat, 29 May 2004 21:50:13 -0500, snipped-for-privacy@xyzzy.stafford.net (jjs) ran around screaming and yelling:

nope...you didn't go for it..<G> JT
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oops. Well just shoot me. Lock, stock and barrel?
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On Sat, 29 May 2004 23:18:02 -0500, snipped-for-privacy@xyzzy.stafford.net (jjs) ran around screaming and yelling:

nah, we like you here....<G> JT
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On Sat, 29 May 2004 18:10:16 -0500, snipped-for-privacy@xyzzy.stafford.net (jjs) wrote:

And tell you what, my son? ;-)

Is that supposed to be news to me? :-X
--
Less drivel, more Dremel.
Always carry a flagon of whiskey in case of snakebite,
  Click to see the full signature.
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-------------------------------------------------------
Dear Tim,
Sure, you can do that. But I've a hunch you can't afford it.
To establish a basis for what follows allow me to define the VW's class of service, which is to spend approximately 98% of its useful life (of about 2000 hours) producing approximately 25% of its potential peak output (Peak is about 60hp for a stock engine). The only time it's asked to produce more -- that 2% figure -- is when the engine is getting the vehicle underway from a dead stop, when it is accelerating or when it is climbing a hill.
The small size of that figure... of the 25%... surprises most people but you can confirm it for yourself from a variety of sources, the handiest being the manuals for a chassis dyno. Lightly loaded, level road, no wind, a bug only needs 12 to 15 hp to maintain 50mph.
When you demand more than that amount of output the engine doesn't explode but it does wear out faster... your TBO or Time Before Overhaul takes a hit. And not a little hit, a big one; the curve for wear in rotating components is not linear, it is eponential.
Maximum Sustainable Output is the power level at which an engine can be operated for a prolonged period (typically 100 continuous hours) (*) without break-down. For air cooled engines MSO is usually determined by how well the engine can cool itself. For a stock VW the MSO is between 55% and 75% of its peak potential output, depending on the ambient air temp & density. (Standard Day, which is kinda cool, you can use the 75% figure.)
So how long will the engine last at that level of output?
About 200 hours. Around then is when one of your exhaust valves will start to fail.
Not to worry. If the engine is properly instrumented and you're right there beside it you'll have plenty of time to shut it down before it swallows the valve and trashes itself.
So how long does it last at full throttle under load? (Hint: It's not rpm alone. It is rpm plus manifold pressure. ie, Maximum Peak Output) Typically around ten hours for a properly built engine.
Those figures are for a stock engine.
Increase the displacement of the engine, you will increase its potential power. When you take advantage of that potential it means you're going to increase the amount of waste heat the cooling system must manage.
So you build yourself a 190hp streeter... and discover it is still using 60hp heads. That's because the size of the heads is determined by the amount of space under the shrouding -- the cooling tin. And you can forget all the bullshit about 'racing' heads and and so on. The cooling equation is super simple with the amount of surface area being the key factor. You can buy after-market heads that use thicker castings but that automatically means they will have less fin area. Ditto for the marvels of aluminum jugs -- the cylinders only have to manage about 17% of the engine's waste-heat budget. The weak link is the heads and at the heads, the exhaust valves and the area around them.
Even a stock displacement engine can produce more waste heat than can be managed by the cooling system. And waste heat management is the key factor in the engine's durability at high levels of output.
So you have yourself a 190hp engine based on VW componets. Probably cost you between five and ten grand. How long it lasts will depend upon the class of service to which it is subjected; how many times you put the hammer down. But it don't take a rocket scientist to see that pumping 190 horsepower's-worth of waste heat through heads designed to handle only 40 means we're not looking a million trouble-free miles here. Or even a thousand, in some cases.
So now that you have that big, powerful engine, how were you planning to get the power to the ground? Yeah, it can be done. But not through the stock power train. Okay, mebbe once or twice. Then it's going to crack across the bottom of the differential housing. If you wanna do more than donuts in the parking lot, you gotta pay for the priviledge. And here again, the durability of the power train is going to be a reflection of its price.
You wanna talk tires? Okay, we can save that part for later. But keep your checkbook handy.
---------------------------------------------
Like I said: Sure, you can do it. The real question is how to pay the bill. And how many times you are willing to do so.
-Bob Hoover
(*) 100 continuous hours on the test-stand is five days. Seven drums of gasoline.
BT, DT and more than once.
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pay
2000
about
that 2%

stop,
you
the
only
but
And
not
without
the
its
(Standard
start to

there
the
rpm
Typically
power.
increase
60hp
of
super
they
The
around
factor in

you
of
But
horsepower's-worth of

looking a

get
the
the
durability
your
bill.
With all due respect, and only since yourself is a stickler for correctness, the original T1 1600 dp engine never exceeded 50hp DIN, the two carbed T3 put out 54 DIN. I know, SAE versus DIN, but we are talking about a German built engine so lets stick to the DIN measure ?! :0)
J.
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---------------------------------------------------
Dear PJ,
I understand what you're saying and agree. Most subscribers to this Newsgroup don't and won't.
Were I to describe the VW as anything other than 60hp most will assume I'm talking about something from 1937 and immediately lose interest. THEIR Volkswagen has 60hp... everybody knows that; even all the magazines say so.
So they think they own a 60hp bug. No problem, I've simply used that as the foundation to support my soap box. Hopefully some of them will get the real message.
-Bob Hoover
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you
of
But
horsepower's-worth of

looking a

................I guess I'm not typing very clearly. I meant to say that I'm looking for about 90 hp, maybe a little more but not much more. My cost is going to run about $1500 but that's because the PO has already put at least $4k into it almost 17k miles ago (full flow Berg oil system with remote filter, new case, machine-in 88mm cylinders, lightened flywheel, Berg heavy pulley, counter-weighted crankshaft, new rods, dynamic balancing, Berg semi-hemi cut heads, solid rocker shafts, 911 swivel foot adjusting screws, Berg oil pump, stock---camshaft-FI type exhaust-L Jetronic FI, etc., etc.). Along with the new level 3 heads, I'm planning to install a 118 grind WebCam & lifter kit. How many miles? I log about 6k miles a year during the warm weather months only. My expectation is to get at least five years of use before replacing the exhaust valves along with whatever else needs attention upon teardown and inspection. Naturally, this is a projection and is possibly unrealistic. I'm committed to handling whatever does happen and will keep this group informed along the way.
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