CAMSHAFT 101

[SamSpade]

Good info ... some related questions:

How is the torque curve influenced by changing the valve clearance? Is the spec 0.30 mm the optimum for both high-rpm driving or streetability? What are the disadvantages of moving away from the spec valve clearance?

[paul burke]

Sammy, lash is dictated by the clearance ramp ground into the cam lobe. Going plus or minus .002 from the recommended clearance is about all you can get away with. Loosening clearance generally improves idle and adds to low speed throttle response. Tightening clearance usually hinders performance on stock engines. If you have ever tightened the lash on an M30 trying to eliminate the valve train noise , you know what I mean.

Paul

[olNick]

Hi,

I'm interested in this topic as I,ve just posted about broken exhaust rockers in the Gen Tech section.
All the broken exhaust rockers (broken at the pad/arm weld) had the cam riding off and striking the edge of them pad, while the intakes still had ~1.5 mm to go before riding off, and none of the broke

I am inclined to think that this is from regrinding w/o any real clue as to what they were doing.

A couple of q's for you guys as I'm trying to visualise this...

The wear pattern I saw on the intakes, as well as some stock exhaust rockers show the wear pattern with the referenced 1.5 mm "unused" area. AFAIU, reground cams end up with a smaller base circle, so this "drops" the rocker, in turn pushes the contact area further out, to the end of the pad?

What is the base circle diameter of the stock cam?
Also, I question that fiddling with the ramp will address this, and in turn the additional lift is limited by the available contact area (which looks minimal to me...)

So, if one cant go to other rockers, I would think that reground cam choice must be pretty limited.

Are the cams referenced above welded up and then ground, as that would, to me at least explain those large lifts.

BTW, Paul do you do n/a cams as well?

Anyway, I'm rambling...

nick

[Brad D.]

The wear pattern I saw on the intakes, as well as some stock exhaust rockers show the wear pattern with the referenced 1.5 mm "unused" area. AFAIU, reground cams end up with a smaller base circle, so this "drops" the rocker, in turn pushes the contact area further out, to the end of the pad?

That is correct. Many times larger eccentrics are required to set the valve lash correctly.
AFAIK Paul uses new billets for all his cams; they are not regrinds.

[paul burke]

Brad, thanks for the plug!

Nick, stock base circle (M30) is 27mm (1.063in) this varies slightly have seen 1.058in on some.

Reground cams create all sorts of valve train issues beginning with the follower as you pointed out.

I do have a number of N/A profiles for the M30.

Be back later with my take on reground cams.


Paul

[iXer]

Paul, I'd like to continue this thread slowly..

I've been thinking about how large profiles you can actually fit in the M30 head without using larger cam journals. What's the limit?

Over at bimmerpro.com I can see you have one profile that lifts 12.29 mm on the intake (0 valve lash?). It's the M30-65-401 and is that's possible without enlarged cam journals?

I know that on the M10 you have to modify and enlarge the cam journals in the head for some of the BMW Motorsport and most aggressive Schrick cams.

And on the flip-side of regrinded cams, at what point does the stock rocker shoe have problems following the cam profile? Does some of your profiles require a larger than stock base circle?
I have the steel rockers I showed you earlier in the thread, and if I ordered a cam from you it would probably be a good idea to send a couple of rockers your way to verify that there is no issue.
At least I know that they work well on the Catcams M10 example earlier.

[paul burke]

Paul, I'd like to continue this thread slowly..

I've been thinking about how large profiles you can actually fit in the M30 head without using larger cam journals. What's the limit?

I would like to go slow also as there are so many details involving lobe design things tend to get convoluted.

If the lobe is a dedicated design meant to be ground on a small base circle such as .950in. like your Cat, then lifts approaching .500 inch plus are possible in an M30 without a journal dia. change. One of the problems with higher lifts (starting at around .475in.) is that you begin to run out of valve spring room (stacking, coil bind). One way to over come the short spring install height is to use a larger off set retainer but this gives you only a little more room. The next is to install longer valves with higher keeper grooves, doing this is advantageous and allows the use of the smaller base circle camshaft while retaining proper vale train geometry.

This is as good a time as any to address reground cams, so here it goes.

Most all regrinds are copies of profiles that began life on a 1.060 base circle. Companies such as Schrick that have access to new blanks (myself included) tend to use standard base circle diameters when grinding cams as it is easier for the customer to install without jumping through hoops to retain correct geometry.

When these profiles are copied on to a used core and there is not enough lobe area to retain the 1.060 base circle, grinders typically reduce the overall lobe size. Kinda like leaving your brand new jeans in the dryer to long!

This method of regrinding proportionally reduces lobe area and greatly effects the profile resulting in improper rocker foot to lobe geometry. It is impossible to copy a profile if the lobe has been reduced in proportion to its original size!!!!!

OK Mattias your turn.

Paul

[paul burke]

I have the steel rockers I showed you earlier in the thread, and if I ordered a cam from you it would probably be a good idea to send a couple of rockers your way to verify that there is no issue.
At least I know that they work well on the Catcams M10 example earlier.

Forgot this one.

As I remember the Owens rockers have a longer pad which makes it even easier to deal with ramp timing.


Paul

[iXer]

Paul, very interesting fact about the different base circles, I never really thought much of it when it comes to cams carved from blanks.

When choosing valve springs, do you put more importance on the seat pressure or the full valve lift pressure?
Is cam/rocker wear a parameter in either measurement?
Or is the main focus on full valve lift and valve speed/acceleration? This is what matters, from what I've been told.

Do you think the valve spring pressures that cam manufacturers recommend for their cams is enough?
I find that Schrick recommends too little, at least for the M20. For the Schrick 304 it seems off, by 10-20 kg. I've seen obvious signs of float and no/little wear on the backside of the cam lobes. Not so strange that people break their rockers..

The above questions are about lobes of course, maybe some don't see it that way. I'm curious, these are things I haven't really considered much. I just got access to a Audie Tech cam measurement system. Trying to make 1+1 = 2, in viewing what you have seen in practice and what you see when you look at the numbers on the screen, is hard but very rewarding.

[paul burke]

Mattias, I adjust spring pressures (rate per inch) relative to the mass the spring has to control and the closing rate of the profile. Although more is taken into consideration, these two areas are the hardest to deal with.

It is fairly easy to control opening events, as long as the follower and valve train remain fully loaded it takes virtually no pressure to control the opening motion, however over the nose and closing events are a completely different story. This is where a well designed profile and a proper valve spring make a huge difference in power. More often its the fault of a poorly designed profile and not the amount/lack of spring pressure that causes seat and valve train issues.

Valve spring design also plays a large part in controlling valve motion. Beyond just rate, the spring diameter (coil length) the wire shape/diameter and the amount of rounds (coils) in the spring play a huge part. Springs go through many dimensional changes when cycling, besides the obvious compressing and rebounding motion the wire is also twisted resulting in an oscillating effect throughout the spring. The energy stored during this motion can send the spring into an uncontrolled state. I have slow motion video somewhere of a valve spring doing a hula dance and leaving the spring seat (head side) @ 7800 RPM and back in complete control @8100 RPM.

Over the years I have turned M10/M30 engines in excess of 9000 rpm and have never had a reason to go over 200lbs of max lift pressure (90/100lbs seat) when using the stock valve train.

Paul

[iXer]

I'm very much with you on how you reason on this, it's good to get some ideas confirmed.

By your choice of spring pressures I get a few ideas about what I've seen happen on the M10/M20/M30 engines with an upgraded cam. A higher seat pressure seems to be key, resulting in better control on the rebounding motion.

[paul burke]

By your choice of spring pressures I get a few ideas about what
I've seen happen on the M10/M20/M30 engines with an upgraded cam. A higher seat pressure seems to be key, resulting in better control on the rebounding motion.

Higher seat pressures will help with control, but there are downsides. Some cams are ground with such aggressive closings that they require more spring pressure than one would normally use. This over time will pound out the valve job, much in the same way continual valve "bounce" does when there is not enough control.

It all comes back to the cam profile and valve train mass/geometry.

When the designs are well sorted the parts will last longer.

There is a saying amongst U.S. cam grinders when conveying the benefits of a well thought out design, "Its easy on the valve train" this phrase is used quite often as a selling point when dealing with road racing and other endurance type applications.


Paul

[iXer]

Paul : I have seen talk of combatting the problem you mention of pounding out the valve job with a wider cut on the 45 degree section of the valve seat.On the intake (and exhaust for cooling purposes) I guess this is a compromise between a nice flowing seat job and longevity.

On another matter, you asked earlier : "Have you swiped the bottom of the rocker foot (in the picture) to measure lobe/foot contact area? "

Since both surfaces aren't flat, how do I go about that?
Either way, I like this wide foot - in combination with a nice oil there shouldn't be much wear at this point.


I'd like to dig deeper into what separates a N/A cam and a turbo cam. Like, what demand does the customer base have that seem to require a larger lobe separation and less lift/duration on the exhaust lobe ?

My own experience with turbo engines comes from using N/A cams as well as "turbo grinds", I much prefer N/A cams if the exhaust side of the engine is designed for it, and there is no real problem in that - in fact I think the engine feels more alive and with an extended powerband. Exhaust back pressure does become a factor and the exhaust manifold design becomes more important with more lift/duration and overlap.
Here one can clearly make a distinction between a "pulse driven" and "flow driven" system, the first clearly can benefit from how the cam operates the exhaust valve while also demanding that pulse preservation is designed into the primaries (length, gas speed) and the shape of the pulse split collector before the turbine.


This is turning into more of an interview with Paul Burke, I hope you don't mind me picking your brains - I think it's very rewarding to get an insight into what your experience has taught you. My intention is not to make your wisdom public knowledge, that's impossible anyway and we're just scratching the surface and I hope it improves your business (not that you aren't busy already).

[FirstFives Dictator]

Great thread. Paul, I'd love any thoughts on testing and verifying correct camshaft installation and timing.

[Coldswede]

I would like to pose a basic question to those in the know here.

What is the main difference between a "NA" Cam and a "Turbo" cam? I would think the "Turbo" cam is more about duration and less lift. I would also suspect the closing side of the cam is steeper to trap the charge in the cylinder.

In effect I suspect the cam shape would be more of a lop sided oval than the egg shape we all picture a cam lobe to be. Am I anywhere near correct?

[LSD3.73]

Mattias, I adjust spring pressures (rate per inch) relative to the mass the spring has to control and the closing rate of the profile. Although more is taken into consideration, these two areas are the hardest to deal with.

It is fairly easy to control opening events, as long as the follower and valve train remain fully loaded it takes virtually no pressure to control the opening motion, however over the nose and closing events are a completely different story. This is where a well designed profile and a proper valve spring make a huge difference in power. More often its the fault of a poorly designed profile and not the amount/lack of spring pressure that causes seat and valve train issues.

Valve spring design also plays a large part in controlling valve motion. Beyond just rate, the spring diameter (coil length) the wire shape/diameter and the amount of rounds (coils) in the spring play a huge part. Springs go through many dimensional changes when cycling, besides the obvious compressing and rebounding motion the wire is also twisted resulting in an oscillating effect throughout the spring. The energy stored during this motion can send the spring into an uncontrolled state. I have slow motion video somewhere of a valve spring doing a hula dance and leaving the spring seat (head side) @ 7800 RPM and back in complete control @8100 RPM.

Over the years I have turned M10/M30 engines in excess of 9000 rpm and have never had a reason to go over 200lbs of max lift pressure (90/100lbs seat) when using the stock valve train.

Paul

Sorry I know this is off topic but I havent really been able to figure out what these M30's like in terms of beign built up. You say you ran this engine up to 9k? what was done to achieve this? How was the head changed/cam used? Could this be a streetable possiblity N/A?

[SamSpade]

It's CAMSHAFT 101, so any info on removal and installation would be helpful.

I know the official way of course is using the BMW special tools 11-1-060, 00-1-490 and 11-1-061:



There's a DIY one here that uses clamps:


Any other ways, ideas and tips to do this cleanly?

[turbodan]

It's CAMSHAFT 101, so any info on removal and installation would be helpful.

Any other ways, ideas and tips to do this cleanly?

You slip the rockers off of thier lobes while rotating the cam. If you do it right you'll be able to relieve the load on the cam, at which point you remove the rocker shafts and rockers. Then the cam comes out. No special tools required.

[FirstFives Dictator]

I have the 'Iron Maiden' BMW tool

It's a little scary to use.

[SamSpade]

You slip the rockers off of thier lobes while rotating the cam. If you do it right you'll be able to relieve the load on the cam, at which point you remove the rocker shafts and rockers. Then the cam comes out. No special tools required.

I tried doing that on the M30B35 head. Wasn't possible (am I missing something?) so had to resort to some ghetto techniques undeserved for an aluminum head. Resulted in some nicks on the camshaft bearing in the head (chamfered since).

I want to be less rough and give more love putting it back in.

[turbodan]

You can definitely do it wrong. I cant tell you which rockers have to be moved and when the cam needs to be turned, I usually just take them apart like a puzzle. Maybe next time I'll take notes.

[Canuck YYC]

Took me two attempts but I managed the no-tool cam extraction. It is possible.

[M. Holtmeier]

I remember the head on our eta was easier to pull the cam out of compared to my m30. I ended up building a tool for the m30 heads.

[iXer]

It's CAMSHAFT 101, so any info on removal and installation would be helpful.

It's more about what cam is best for you, not how to wrench with the stock cam - that has been covered over and over on all BMW forums.

[lito]

hi mr burke ,pls guide me in selecting cams for my turbo m90 engine.pls view my dyno sheet at our dynodatabase.i want to improve my top end power.i want my engine to rev 7000-7500rpm range without too much loss in its torque curve ..is that possible?