TUNING The 8v Camshaft Thread..

[bored_Welsh_lad]

This information has been taken from Club.Broke.Status website, i do not know enough about cams to answer any questions that this information does not answer...

A Brief Introduction into Camshafts.

Below are a few pieces of referece material to help visualize things that are discussed later on......
Here we have a photo description of EVERY part of a camshaft/lobe:



to help visualize the 4 stroke combustion process, refer to this:
EXHAUST SIDEINTAKE SIDE

Stock camshafts are designed by the manufacturer to have a smooth idle and give optimum fuel economy with excellent drivability from idle to a modest redline. While this is ideal for “normal” cars, it is a hindrance when building an engine for all-out performance. Replacing your stock camshaft with a more aggressively-ground camshaft is the first step in letting your head move air more efficiently. Greater volumetric efficiency produces horsepower and torque.

Camshafts are sold by their Advertised Duration number. This number represents the actual seat-to-seat duration (as expressed in crankshaft degrees) taken at a .1mm checking height. When choosing a camshaft, the advertised duration will give you an idea as to where the power band will be. Generally speaking, a higher duration number translates into your usable power band being pushed further up the rpm range.

The Lobe Separation Angle (LSA) of the camshaft lobe is where the peak lift occurs in crankshaft degrees either BTDC or ATDC. The LSA is the result of your lobe centerlines added together, then divided by two. Some camshafts are ground with identical lobe centers (e.g. 110° + 110° / 2 = 110°) while others have mismatched lobe centers (e.g. 109.5° + 110.5° = 110°). Although both cams share the same 110° Lobe center, their performance will be much different. The LSA will be a determining factor in what your valve overlap will be in relation to the duration you decide to go with. High-duration camshafts with wide LSAs (e.g. between 106°-110°) are ideal for upper rpm power and produce a lumpy idle. Narrower LSAs (e.g. 111°-115°) accentuate low-end torque and provide a smoother idle.

Lift is the total amount of valve movement created by the camshaft. Increased valve lift increases the total amount of power made over the entire rpm band. Watercooled VW/Audi heads use cam followers between the lobe and the valve stem. This means that the total lift provided from the camshaft lobe is the same lift that the valve will see.

It is important to remember that “bigger is better” does not apply here and that over-camming a head is a rookie mistake. Make sure you do your homework before investing. A camshaft well-matched to the head’s flow characteristics will deliver maximum torque and power across the desired power band. A cam that is ill-matched to the engine’s spec or the application (e.g. commuter vs. rally vs. drag) may make a vehicle slower if not simply unpleasant to drive.

CALCULATING DURATIONS

Let us review the four strokes again and add some timing events to calculate the total valve duration. For illustrative purposes, we can discuss a good street cam with a 268 degree duration and 108 degree lobe centers. (The lobe center angle is the angle in camshaft degrees between full intake cam lift and full exhaust cam lift). As we discussed above, at the end of the fourth stroke both valves are open and the next stroke is the intake stroke. Referring to the engine .gif up top, we see that the intake valve began to open at 26 degrees BTDC. The piston moves down the cylinder after the crankshaft passes TDC, and the valve reaches full lift at 108 degrees ATDC (lobe center). Note also that the intake valve is still open when the piston reaches BDC. We can start to add things up now. The crankshaft has rotated 180 degrees from TDC to BDC on the first stroke and the intake valve opened 26 degrees BTDC, so the total crankshaft rotation so far is 26 + 180 = 206 degrees. We started with a 268 degree camshaft so that tells us when the intake valve will close: 268 - 206 = 62 degrees ABDC. Note that even though the second stroke is the compression stroke, we see that it starts while the intake valve is still open!

VW Owners Opinions on Camshafts


--A total valve lift of .432" is the generally accepted lift ceiling on camshafts for heads with OEM single valve springs. (Generally, but not limited to, all OBDII heads) It is strongly suggested upgrading to an HD dual valve spring set-up mainly due to the strength of the spring cannot handle sustained high rpms without incurring valve float. Coil bind is also an issue, and occurs as soon as .440".

--It is of my own personal opinion that camshafts with lifts higher than .432", but up to .449", can be used as long as normal driving conditions are adhered to. Damage to the engine will inevitably occur if driven beyond the OEM single valve spring's ability. I personally would never suggest anyone run their engine in this manner. Coil bind (coils touching) occurs as soon as a .440" lift and I have a OEM valve srping to prove this. Don't ever go cheap; ALWAYS replace/upgrade the first time around.

--Earlier heads come factory with a dual spring setup. These dual springs can safely handle a high lift camshaft. Keep in mind that these are not considered a heavy duty dual spring setup and may cause issues on really aggressive camshafts. Upgrading to a heavy duty spring set is strongly reccomended for engines that frequently see sustained high rpms. (I.E auto cross, drag racing, hill climb, ect)

--It is also strongly recommended that new cam followers (aka lifters) be used when installing a new camshaft. Flat tappet cams sometimes have taper across the face of the lobe. The tappet will have a slight convex radius to match this taper. When camshafts break-in the taper over the nose and the radius of the lifter is slightly worn in. If you run a lifter with a reduced (worn) radius against a new lobe with correct taper, the edge of the lobe will have concentrated loading. This high load can cause the camshaft material to break down rapidly causing a failure.

Common Camshaft Myths

Myth #1: As stated in ads..."Techtonics 266* (aka 270*). I don't know where or who started this marketing scheme, but I just want to clarify this. These are actually two slightly different cam profiles...the 270* having more duration and lift. They do share the same center lines. Power delivery is virtually the same between the two.

Myth #2: "You cannot run a cam bigger than a 260* within a single valve spring head." Duration has nothing to do with the amount of lift a valve spring can handle. I believe this myth was adopted because one of the more famous camshafts, the Techtonics 260*, has a.432" lift. (which has been the understood lift celing for OEM single valve spring heads).
There are a handful of camshafts available on the market that offer larger-than-260* durations.

Myth #3: Camshaft break-in procedures: "You gotta drive 500 miles to break it in." Proper break-in for a new camshaft is 20 minutes at a varying 1900-2100rpms

Myth #4: "You cant run high duration camshafts with a turbo/supercharger." Acutally, you can. Knowing the specs of the camshaft is vital, though. Remember, while some valve overlap is good with forced induction, too much, and you blow all your boost out the back of the car. Pay close attention to the lobe centers of the cam and the overlap of the intake/exhaust valves. There are quite a few 268*-272* duration cams on the market that do very well in forced induction applications.
Little know fact...the Neuspeed 268* is actually their upgrade cam for their supercharger. (you won't find that wirtten on their site, though.) Why? 113* lobe center!

[bored_Welsh_lad]

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The following contains camshaft options available for the MKIII/MKIV 2.0 Liter.

I will try to give the most info I can regarding overall grind specifications, but please be aware, not all manufactures display their grind specs. In these instances, they will be noted as 'Unkown'. For the time being, I will only be adding HYDRAULIC camshafts. In all instances, intake precedes exhaust in the descriptions.

Camshafts that require valvetrain upgrades will be preceded by an asterisc (*).

OBDI camshaft measured @ .050"
Advertised Duration: Unknown
Duration @ .050": 211*/212*
Valve Lift: .400"
Lift @ TDC: Unknown
Centerlines: 113.2* / 113.8*
Lobe Center: 113.5*
Valve Timing: -7.7/38.7 - 39.8/-7.8
Valve Overlap: -15.5*

OBDII camshaft measured @ .050"
Advertised Duration: Unknown
Duration @ .050": 210*/210*
Valve Lift: .417"
Lift @ TDC: Unknown
Centerlines: 110.8* / 109.2*
Lobe Center: 110*
Valve Timing: -5.8/35.8 - 34.2/-4.2
Valve Overlap: -10*[/quote]

VW diesel cam specs

ALH camshaft measured @ 1mm
Duration @ 1mm: 189*/189*
Valve Lift: .337”/.337”
Centerlines: 110.5*/113.5*
Lobe Center: 112*
Valve Timing: @ 1mm -16/25 – 28/-19
Valve Overlap: @ 1mm -35*

SDI camshaft measured @ 1mm
Duration @ 1mm: 194*/210*
Valve Lift: N/A
Centerlines: 108*/115*
Lobe Center: 111.5*
Valve Timing: @ 1mm -11/25 – 40/-10
Valve Overlap: @ 1mm -21*

AAZ camshaft measured @ 1mm
Duration @ 1mm: 194*/199*
Valve Lift: .337”/.332”
Centerlines: 103*/106*
Lobe Center: 104.5*
Valve Timing: @ 1mm -6/20 – 25.5/-6.5
Valve Overlap: @ 1mm -12.5*




--------------------------------------------------------------------------------------------

Aftermarket Cams

Schrick

*260 camshaft measured @ .004”
Advertised Duration: 260*/260*
Duration @ .004 260*/260*
Valve Lift: .433” / .433”
Lift @ TDC: .023"/.027"
Centerlines: 116*/116*
Lobe Center: 116*
Valve Timing: 14/66 – 66/14
Valve Overlap: 28*

268 camshaft measured @ .004”
Advertised Duration: 268*/268*
Duration @ .004 268*/268*
Valve Lift: .441” / .441”
Lift @ TDC: .047"/.047"
Centerlines: 113*/113*
Lobe Center: 113*
Valve Timing: 21/67 – 67/21
Valve Overlap: 42*

*272/268 camshaft measured @ .004”
Advertised Duration: 272*/268*
Duration @ .004 272*/268*
Valve Lift: .449” / .449”
Lift @ TDC: Unknown
Centerlines: 110*/112*
Lobe Center: 111*
Valve Timing: 26/66 – 66/22
Valve Overlap: 48*

*272/272 camshaft measured @ .004”
Advertised Duration: 272*/272*
Duration @ .004 272*/272*
Valve Lift: .449” / .449”
Lift @ TDC: .063"/.067"
Centerlines: 111*/111*
Lobe Center: 111*
Valve Timing: 26/66 – 66/26
Valve Overlap: 52*

* 268/276 (G60) camshaft measured @ .004”
Advertised Duration: 268*/276*
Duration @ .004 268*/276*
Valve Lift: .441” / .452”
Lift @ TDC: .051"/.071"
Centerlines: 112*/112*
Lobe Center: 112*
Valve Timing: 22/66 - 070/26
Valve Overlap: 48*

*276 camshaft measured @ .004”
Advertised Duration: 276*/276*
Duration @ .004 276*/276*
Valve Lift: .453” / .453”
Lift @ TDC: .083"/.083"
Centerlines: 110*/110*
Lobe Center: 110*
Valve Timing: 28/68 – 68/28
Valve Overlap: 56*

*288 camshaft measured @ .004”
Advertised Duration: 288*/288*
Duration @ .004 288*/288*
Valve Lift: .461” / .461”
Lift @ TDC: .134"/.134"
Centerlines: 109*/109*
Lobe Center: 109*
Valve Timing: 34/74 - 74/34
Valve Overlap: 68*[/


Cat Cam
258 camshaft measured @ ..050 / 1mm
Advertised Duration: 258*
Duration @ ..050”* 224*/224*
Duration @ 1mm: 230*/230*
Valve Lift: .419”/.419”
Lift @ TDC: .067”/.065”
Centerlines: 109*/109*
Lobe Center: 109*
Valve Timing: @ .050" 3/41 – 41/3
Valve Timing: @ 1mm 6/44 – 44/6
Valve Overlap: @ .050” 6*
Valve Overlap: @ 1mm 12*

* 261 camshaft measured @ ..050 / 1mm
Advertised Duration: 261*
Duration @ ..050”* 220*/220*
Duration @ 1mm: 226*/6*22
Valve Lift: .456”/.456”
Lift @ TDC: .047”/.047”
Centerlines: 110*/110*
Lobe Center: 110*
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


* 262 camshaft measured @ ..050 / 1mm
Advertised Duration: 262*
Duration @ ..050”* 226*/226*
Duration @ 1mm: 231*/231**
Valve Lift: .441”/.441”
Lift @ TDC: .049’/.053”
Centerlines: 113*/113*
Lobe Center: 113*
Valve Timing: @ .050": 0/46-46/0
Valve Timing: @ 1mm: 2/49-49/2
Valve Overlap: @ .050”: 0*
Valve Overlap: @ 1mm: 4*


266/267 camshaft measured @ ..050 / 1mm
Advertised Duration: 266* / 267*
Duration @ ..050”*
Duration @ 1mm: 228*/228*
Valve Lift: .429” / .429”
Lift @ TDC: .057”/.055”
Centerlines: 110*/110*
Lobe Center: 110*
Valve Timing: @ .050": Unknown
Valve Timing: @ 1mm: 4/44 – 44/4
Valve Overlap: @ .050”: Unknown
Valve Overlap: @ 1mm: 8*


273 camshaft measured @ ..050 / 1mm
Advertised Duration: 273*
Duration @ ..050”: 230*/230*
Duration @ 1mm: 236*/236*
Valve Lift: .431*/431*
Lift @ TDC: .067”/.067”
Centerlines: 110*/110*
Lobe Center: 110*
Valve Timing: @ .050": 3/47 – 47/3
Valve Timing: @ 1mm: 6/50 - 50/6
Valve Overlap: @ .050”: 6*
Valve Overlap: @ 1mm: 12*


273 camshaft measured @ ..050 / 1mm
Advertised Duration: 273*
Duration @ ..050”: 230*/230*
Duration @ 1mm: 236*/236*
Valve Lift: .431*/.431”
Lift @ TDC: .078”/.077”
Centerlines: 112*/112*
Lobe Center: 112*
Valve Timing: @ .050": 5/45 – 45/5
Valve Timing: @ 1mm: 8/48 – 48/8
Valve Overlap: @ .050”: 10*
Valve Overlap: @ 1mm: 16*

* 275 camshaft measured @ ..050 / 1mm
Advertised Duration:
Duration @ ..050”*
Duration @ 1mm:
Valve Lift:
Lift @ TDC:
Centerlines:
Lobe Center:
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


* 279/278 camshaft measured @ ..050 / 1mm
Advertised Duration:
Duration @ ..050”*
Duration @ 1mm:
Valve Lift:
Lift @ TDC:
Centerlines:
Lobe Center:
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


* 279 camshaft measured @ ..050 / 1mm
Advertised Duration:
Duration @ ..050”*
Duration @ 1mm:
Valve Lift:
Lift @ TDC:
Centerlines:
Lobe Center:
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


* 283 camshaft measured @ ..050 / 1mm
Advertised Duration:
Duration @ ..050”*
Duration @ 1mm:
Valve Lift:
Lift @ TDC:
Centerlines:
Lobe Center:
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


* 283 camshaft measured @ ..050 / 1mm
Advertised Duration:
Duration @ ..050”*
Duration @ 1mm:
Valve Lift:
Lift @ TDC:
Centerlines:
Lobe Center:
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


* 283 camshaft measured @ ..050 / 1mm
Advertised Duration:
Duration @ ..050”*
Duration @ 1mm:
Valve Lift:
Lift @ TDC:
Centerlines:
Lobe Center:
Valve Timing: @ .050"
Valve Timing: @ 1mm
Valve Overlap: @ .050”
Valve Overlap: @ 1mm


Piper
*264 camshaft measured @ .004”
Advertised Duration: 256*/260*
Duration @ .004 260*/264*
Valve Lift: .417” / .428”
Lift @ TDC: Unknown
Centerlines: Unknown
Lobe Center: 110*
Valve Timing: 18/58– 62/22
Valve Overlap: 40*

[bored_Welsh_lad]

What Does It All Mean?


Here are the general terms and definitons associated with the parts within your head.


FLAT TAPPET CAMS are cams designed for use with either hydraulic or solid lifters (but not both) with a bottom surface which is nearly flat. I say nearly flat because these lifters are actually slightly convex in shape. When the convex surface of the lifter matches with the slightly angled surface of the cam lobe (the portion of the camshaft that creates valve train movement) the lifter will rotate in its bore. If the lifter doesn't rotate for any reason the cam and lifter will wear out very quickly.

HYDRAULIC CAMS use lifters that utilize the engine's oiling system to automatically adjust the valve lash (clearance) to zero. They are the only type of lifters used on VW heads 1985<present.

MECHANICAL/SOLID CAMS use a solid (lifter) which requires regular valve adjustment. Some performance shops prefer solid lifters, even for street use, because they can adjust the way a cam will perform to a limited extent by changing the amount of lash (clearance) in the valve train. Decreasing the lash increases the duration and lift, increasing the lash decreases the duration and lift. VW used these up till 1984 when they switched to a hydraulic lifter head.

DURATION is the length of time that the valve is held open by the cam. This is measured by the degrees that the crankshaft rotates. More degrees of duration will make the engine operate in a higher rpm range. There are two ways of rating duration:

**ADVERTISED DURATION was originally the S.A.E. (Society of Automotive Engineers) standard as measured from .006" of valve lift. Over the years this has been altered by most performance cam makers to make their cams look hotter, or different, than the specs of their competitors. Valve lift points as low as .002" are sometimes used and this can add up to thirty degrees to the advertised figure. Even when the cams being compared are all measured the same way the figures can still be misleading if you don't know what the cams were designed for. Cams designed for quiet street operation will show higher .006" duration numbers than performance cams of the same rpm range.

**DURATION MEASURED FROM .040” (1mm), or .050" of cam lift is the best for comparison of specs because most of the variations in cam design are reduced and the valves are open enough to start getting some flow past them. Most cam makers give accurate ratings and good comparisons are possible between cams of the same type (hydraulic or solid or roller).

LIFT is usually measured as gross (total) valve lift. This works for hydraulic lifter cams but is misleading for solid lifter cams because you must subtract the valve clearance to get the net (real) valve lift.

LOBE AREA is obtained by measuring the lift at each degree of rotation and adding them all together. This will tell you very quickly how much difference (if any) there is between two cams with the same lift and duration. This is rarely supplied by cam makers.

CENTERLINES are the degrees the crankshaft turns from top dead center to the center of the top of the cam lobe (nose of the cam). If you add the centers of both cam lobes together and divide by two you will have the lobe center separation.

LOBE SEPARATION ANGLE is the degrees the cam turns from the center of the exhaust lobe to the center of the intake lobe on the same cylinder. Wide centerlines (113*) give minimal valve overlap, while on narrow centerlines (108*), more ovelap is available.

VALVE LASH is the amount of clearance required at the valve tip with mechanical/solid lifters cams.

VALVE TIMING is the opening and closing points of the valves measured in relation to the degrees of crankshaft rotation. These specs are often given by both the advertised and the .040"/.050" methods. These points can be advanced or retarded (as a group) after installation with an adjustable cam gear.

ASYMMETRICAL CAM LOBES are designed with the closing side of the lobe different in shape than the opening side. This difference is only visible in some overhead cams. When both sides are the same they are SYMMETRICAL.

ASYMETRICAL CAM DURATIONS are split duration samshafts where the intake side is of a different duration than the exhaust side. Forced Induction-specific cams utilize this aymetric design to allow for more duration, yet keep a wide enough centerline as to keep valve overlap to a minumum.

BASE CIRCLE, or the heel, is the round portion of the cam lobe. This is where the lifter rides while the valve is closed. VW hydraulic camshafts have a 1.34" base circle, where a mechanical./solid lifter cam has a larger 1.5".

BILLETS and CORES are the blank shafts that the camshafts are made from. CAST CORES and PROFERAL IRON BILLETS are used for most flat tappet camshafts. STEEL BILLETS are used for roller tappet camshafts.

CAM LOBES are the parts of the camshaft that create the valve movement.

CAM PROFILE or CAM GRIND is the actual shape of the cam lobe.

CLEARANCE RAMPS are the portion of the cam lobe between the base circle and where the valve starts to open. They slowly take up any slack in the valve train and reduce the shock created by the sudden movement of the lifter.

FLANKS are the sides of the cam lobe that cause the movement that raises and lowers the valve. They are also called the OPENING and CLOSING RAMPS.

NOSE of the cam lobe is the portion of the lobe with the highest lift.

RATE OF LIFT refers to the speed that the valve opens and closes. Cams with a higher rate of lift have more lobe area to provide performance gains.

VALVE OVERLAP is the term used when the piston is at top dead center and both the intake and exhaust valves are off their seats the same amount. With a single pattern cam this would mean that the camshaft was timed straight up. Advancing or retarding the camshaft will open one of the valves more at top dead center and reduce the valve to piston clearance.

VALVE FLOAT happens when the speed of the engine is too great for the valve springs to handle. The valves will stay open and/or "bounce" on their seats. The clearance in the valve train created by valve float will also cause hydraulic lifters to "pumpup" as they try to eliminate the valve clearance.

PUMP-UP happens in stock hydraulic lifters at high rpm. They simply can't handle the volume of oil and the extra operating speeds so they expand, or pumpup, causing the valves to stay off their seats slightly even while the lifter is on the base circle of the cam.

VALVE LASH is the amount of clearance, measured at the valve, in the valve train when using a mechanical/solid camshaft.

VALVE TRAIN reffers to the parts leading from the cam lobe to the valve.

[Adam]

Your on one! Nicely done

[bored_Welsh_lad]

just trying to find out the standard camshaft duration on an 8v because i dont think its anywhere near 270 and stumbled across this lot...

[gtigolfthree]

That'll keep you from being bored.  Interesting read though. 

[bored_Welsh_lad]

lol.. it didnt take long to find that lot.. from reading it though it the aba to have a 217/215 (inlet/exh) at .050 or if you read..

OBDII camshaft measured @ .050"
Advertised Duration: Unknown
Duration @ .050": 210*/210*
Valve Lift: .417"
Lift @ TDC: Unknown
Centerlines: 110.8* / 109.2*
Lobe Center: 110*
Valve Timing: -5.8/35.8 - 34.2/-4.2
Valve Overlap: -10*

then its 210...

from reading this..

DVERTISED DURATION was originally the S.A.E. (Society of Automotive Engineers) standard as measured from .006" of valve lift. Over the years this has been altered by most performance cam makers to make their cams look hotter, or different, than the specs of their competitors. Valve lift points as low as .002" are sometimes used and this can add up to thirty degrees to the advertised figure. Even when the cams being compared are all measured the same way the figures can still be misleading if you don't know what the cams were designed for. Cams designed for quiet street operation will show higher .006" duration numbers than performance cams of the same rpm range.

even if you add the max 30 degrees  for .002'' lift you still only get240 or for the top figs 247.. which is still nowhere near what was quoted in the other cam thread, which i believe was something like 270..

Also.. why would so many manufactorers be creating cams that have a lower cam profile than the standard cam yet still see gains in power???

[axewielder]

ive got some figures at home will post up when found

[bored_Welsh_lad]

Good info, I still think the standard cam is more than 210 degrees.

Thats what i explained above.. cam duration quoted at 0.006'' lift.. right near the top of the lobe.. but people quote the actual duration from 0.050'' so lower down the side of the lobe as ther is less chance of error and its easier to compare cams at this point...

hense what i quoted above.. refering to ACTUAL duration and ADVERTISED duration.. ADVERTISED is taken right near the top of the lobe, where as ACTUAL is further down the lobe and hense a smaller number..

That information goes on to say...that some companies take it as low as 0.002 .. which would provide a figure of up to 30 degrees more...

So therefore.. even if VW were working from the 0.002 point.. there cam would only be a 240 degree cam..does that make sense???

[danny_p]

iirc  stock cam is 234 deg