Rocker ratio airheads

[RGregor]

SS, cool down.
I thought it was very simple. The question that arose here, whether BMW specs are right or not, will not be answered by talking. How could it?
This simply takes some work: timing a 336.
Now, who could do that?
Know anyone having such a cam in his engine?
And having the skills and knowledge .....
Now, if you doubt the specs, then measure and prove they're wrong.
What's so difficult to understand about that?

[supershaft]

Originally Posted by RGregor

SS, cool down.
I thought it was very simple. The question that arose here, whether BMW specs are right or not, will not be answered by talking. How could it?
This simply takes some work: timing a 336.
Now, who could do that?
Know anyone having such a cam in his engine?
And having the skills and knowledge .....
Now, if you doubt the specs, then measure and prove they're wrong.
What's so difficult to understand about that?

Cool down? Give me a break! I am not the one going on and on with personal crap like you guys have been doing for months now. Cracking up is laughing, not steaming! Do you read my posts? I never said I doubt the specs. I said that I believe they are cam specs and the reasons why I suspect and hope they are. Meanwhile, you and others are up to your usual crap. Where do you come up with this stuff? I have told you numerous times now why I have as yet not timed my cam. Now that I want to I am going to have to get a degree wheel. Until now, I have just used the shop's working for hire or used a friends. Before I get one I want to decide what size I am going to get. I think I am going to get a monster one for now and just time them out of the frame.

[bereahorn]

While looking at Snowbum's site for something else, I ran across this section and thought it might hold some information of interest for this thread. And by the way, I'm just the messenger.

7. BMW camshafts: This is a VERY confusing subject for many folks. Besides the confusion on camshafts, there are sprocket complications. There are several stock camshafts, and some available camshafts. For the stock cams, at .080" valve clearance, the timings are as follows, keep in mind that TWO types of these are available, the 3° advanced one and the NOT advanced one. There are a number of stock camshafts, 284°, 308°, and also a 336 degree.

R50/5, R60/5, and R60/6 (to 1975): INtake opens 40 ATDC; closes 40 ABDC. EXhaust opens 40 BBC; closes 40 BTDC.
R60/6 1976 and R60/7 1977: INtake opens TDC; closes 40 ABDC. EXhaust opens 40 BBDC; closes TDC.
R60/7 1978: INtake opens 6 BTDC; closes 34 ABDC. EXhaust opens 46 BBDC; closes 6 BTDC.
R75 and R90; R100/7; R100S; R100RS 1977: INtake opens 10 BTDC; closes 50 ABDC. EXaust opens 50 BBDC; closes 10 BTDC. (This is the symmetrical cam talked about a bit farther down in this section #7)
R80/7, R100/7, R100S, R100RS (1978): INtake opens 16 BTDC; closes 44 ABDC. EXhaust opens 56 BBDC; closes 4 BTDC. (This is the advanced cam talked about a bit farther down in this section #7)
From 1978, the U.S. models (R80/7 and larger) had INtake opening 10 BTDC; closing 44 ABDC; EXhaust opening 56 BBDC; closing 4 ATDC.


note that sometimes cams are spoken about as the total degrees, and the 1978 would be 308°

see: http://www.softcom.net/users/W6rec/duane/bmw/engine.htm
also see Clymers, Haynes, the BMW books, etc.

336 degree camshafts, the so-called sport cams are the ones ending in part number -053, -412, and -393, see below and note that the last batch of the 336 cams was for the square drive oil pump, and the cams come with the oil pump parts.

NOTE #1: The 336 cam has about a .424" lift, soft ramps, and runs strongly between 5700-7700 rpm, with roughly 8000 max rpm.

NOTE #2: BMW uses .080" of valve setting clearance ( 2.0 mm) as the reference point for cam timing, and the tolerance on timing is + or - 2.5°. Also note that if you are measuring at the CAM lobe itself, that the R60/7 had a 0.2417" lift; and the later larger bore engines had 0.2634" lift. NOTE however that the rocker arm ratio on all the engines is 1.39, so for valve lift you multiply the cam lobe lift by that 1.39 factor.
Another way of saying all this is that the valve pockets in the pistons might have to be modified. The 284° camshaft has 8.62mm lift; the 308° camshaft has 9.40 mm lift, for some reference points here.

11-31-1-258-053 has small cam seal, used on /5 to R90S (to 1976 model year); and was replaced by the -337-848 cam per book, in error, says K.
11-31-1-263-412 has large cam seal, used on R60/6-R100/7 (to 1979 model year); replaced by the 337-843 for both /5 and /6.
11-31-1-336-393 used on canister ignition models, from 1979, including the R65 (?). This cam has a slot on the front face.

NOTE #3:...to further confuse the issue, there were TWO versions of the -053 and -412 camshafts. The difference is the KEYWAY for the gear. The later versions is advanced 3°, so the valve timing versus the crankshaft is changed 6°. The -393 flat nose cam is available ONLY in the advanced version.
The cams are not easily identified by appearance, and must be measured. If an old cam is installed in a 1979+ engine, the slot is retarded 3 degrees.
Here is the timing for these sport cams:
ZERO degree cam: INtake opens 32 BTDC; closes 52 ABDC. EXhaust opens 52 BBDC; closes 32 ATDC.
THREE degree cam: INtake opens 38 BTDC; closes 46 ABDC. EXhaust opens 58 BBDC; closes 26 ATDC.

NOTE #4: UNconfirmed data for the sport cams, where P=(inches):
4000 rpm, 3° cam, P= 46. For 6000 rpm P=30. For 7000 rpm, P= 25.
for the zero degree cam, add about 2 to the P figures above.

The entire camshaft story is very complex, and I am not going to put it all in this article, but, refer you to someone else's article:
http://moragafalconers.org/BMW_336_cam/
That is a link to an article that was translated and edited by David Paulus. I think that on the first page there is an error in the part number for the item 2 cam, which should be, I think, 11-31-1-263-412, and, that it is questionable that the cams won't fit the R45 and R65. One additional note: under figure @1, at C., it describes a 'suitable washer'. Try 11-34-0-026-186, as originally used on the R69S. NOT cheap! The washer is tough, made of fibre, and insulates the spring from heat, when the engine is suddenly stopped.


NOTE #5: In 1977-78 BMW made changes, that amounted to a 6° difference in timing. This was done by changing the keyway in the camshaft sprocket. Because of this, if one uses the 1978 camshaft, and then uses a 1977 sprocket (11-31-1-250-253), then the timing is retarded. Engines/bikes imported to the U.S. from roughly January 1st of 1978 HAD to have the advanced timing, to meet the 1978 emissions rules. Many just before this date did NOT. Thus some "1978" might not have the emissions camshaft.
Here is a sneaky way of determining things, an edited version of something passed on by Tom Cutter:
Remove the spark plugs and valve covers. Put bike in 5th gear and rotate the rear wheel in the forward direction until the EXHAUST valve rocker arm pushes the valve inwards and then JUST returns ALMOST all the way outwards. As you rotate the wheel (jerks work fine on the gear backlash for that purpose) and the exhaust valve starts to come back out, the intake will start to go in. This is the overlap phase. Lay a straight edge across the adjustment LOCKnuts, from the exhaust to intake rockers. Looking straight down on the rockers, and on the straight edge from above, the straight edge will change angle relative to the valve cover gasket, as you turn the rear wheel. STOP when it is parallel. At this point, if OT mark is lining up in the window, the cam is symmetrical. If it is about 3/8" below the window, it is the advanced timing cam.

[MotoKaw]

Would these tools help? -

http://www.andrewsproducts.com/ezcam/key-features

http://www.andrewsproducts.com/cam-d...esign-software

I thought this tidbit from the Smooth4W (Cam Data Analysis Program) summary was noteworthy:

"Smooth4W can also import valve lift data (not cam lift) and convert it to cam output. If you have a valve lift curve and need to generate data for manufacturing a cam lobe to produce correct finger follower valve motion for your engine, Smooth4W can do it."

Constructive thoughts?

Bob

[RGregor]

Originally Posted by supershaft

Cool down? Give me a break! I am not the one going on and on with personal crap like you guys have been doing for months now. Cracking up is laughing, not steaming! Do you read my posts? I never said I doubt the specs. I said that I believe they are cam specs and the reasons why I suspect and hope they are.

The bulletin clearly speaks of valve lift. You believe it must be cam lift. So you doubt the bulletin. This point is crucial for timing and thus the specs. So you doubt the specs.
This is very simple.

All I mean is, if you doubt it, prove it to be wrong.
Until then you shouldn't build an argumentation on your hopes, calling anyone an idiot not believing in you.
Again very simple.

So do us all a favour, time your cam and deliver data. Not hopes.

[chasbmw]

Berahorn,

The snow bum information is interesting, but since it was last revised there is a much wider choice of camshaft available, in the old days it was either the stock 308 degree cam or a 336 and that was about it unless you were unlucky enough to fit an Andrews sports cam.
Take a look at the Motoren Israel web site and you will find a much wider variety of cams.

Snow bums article has reminded me that with airheads the devil is in the detail, if you are building a pre 81 engine out of parts, unless you check the cam timing, it would be easy to end up with a bike that runs badly and you would have no idea what caused the problem.

[RGregor]

A friend has timed all airhead cams he could get hold of, measuring valve lift in 2° crank angle steps with digital gauges with a resolution of 1/100 mm. He measured lift at the retainers.
He gave the data to me for my personal use, not to publish them in a forum, but today I'll make an exception.

I took the data for the 336 and determined the angles corresponding to 2mm valve lift and 2*1,39mm lift (2mm cam lift).

The angles are

	Ex-open	Ex-close	In-open	In-close
Measurement	50	32	30	54	(2mm valve lift)
Measurement	40	24	20	42	(2mm cam lift)
BMW Spec	52	32	32	52	(2mm ????? lift)

Feel free to determine what the ?????? mean.

[chasbmw]

Thanks Rudi, you have proved your point thanks for all your usefull and pertinent info.

I will also share my info on the 320 cam when I have done the work.

[RGregor]

Originally Posted by chasbmw

Thanks Rudi, you have proved your point

There was nothing to prove.
My point was not that the BMW specs were right in any case.
I didn't know myself prior to verifying.
It simply was how to behave having little or null knowledge.

[RGregor]

Originally Posted by supershaft

Do you read my posts? ..... I have told you numerous times now why I have as yet not timed my cam.

Yes I did. Not all but many.
Re-reading the posts in the cam thread is very funny now.
http://www.advrider.com/forums/showthread.php?t=804634

Especially regarding the fact, that except PJ no one here has timed his 336. Not you, not the "crowd in the back".
Again a very good example on how some people behave.

Regaring the numerous times you told me ....

I have told you a few posts ago that until then I didn't know it, in fact I have never read the slightest hint in that direction and I would be very surprised if we found these info in any of your posts here.

So, I don't know whom you talk to and how.
But stop it, it's not me.

[supershaft]

Originally Posted by RGregor

Yes I did. Not all but many.
Re-reading the posts in the cam thread is very funny now.
http://www.advrider.com/forums/showthread.php?t=804634

Especially regarding the fact, that except PJ no one here has timed his 336. Not you, not the "crowd in the back".
Again a very good example on how some people behave.

Regaring the numerous times you told me ....

I have told you a few posts ago that until then I didn't know it, in fact I have never read the slightest hint in that direction and I would be very surprised if we found these info in any of your posts here.

So, I don't know whom you talk to and how.
But stop it, it's not me.

What are you going on about now? I never said anyone was an idiot. That was you. Stop putting words in my mouth but without putting words in my mouth you have nothing to go on about. It's pretty pathetic.

You would be very surprised to find any of [these] info here in my posts? What you ignore in my posts and what you make up that you read in my posts is never ending. My advise is to concentrate more while you are reading and then refrain from making up rude comments.

Are BMW cam specs valve specs? No one here still knows for sure yet. At least now you know what the lift check point is and that there is a difference between valve timing and cam timing with our engines and why most smart tuners stick with cam timing. Even why most timing specs regarding OHV engines that are labeled as cam specs are in fact cam specs versus valve specs. Valve specs or cam specs, at least BMW gives a lift check point with their specs so you can actually use them. Those reported variations? Are the variations the cam or the rocker arms?

[RGregor]

Originally Posted by supershaft

What are you going on about now? I never said anyone was an idiot. That was you. Stop putting words in my mouth but without putting words in my mouth you have nothing to go on about. It's pretty pathetic.

Now, if my tone was rude what especially is the following? Isn't that calling some people here idiots? Of course not directly ...

Originally Posted by supershaft

You guys are cracking me up! Only here on the idiotnet .......Damned Human Nature Rampant on the Idiotnet!

Look if you find the word idiot in my posts. Or even the implication I may regard someone being one. If you find it I'll owe you a beer.

Originally Posted by supershaft

You would be very surprised to find any of [these] info here in my posts? What you ignore in my posts and what you make up that you read in my posts is never ending. My advise is to concentrate more while you are reading and then refrain from making up rude comments.

If I ignore facts in your posts I apologise. But I think exactly this of you. Ignoring what doesn't fit your points of view.

But if yout told me numerous times why you didn't time your cam and I don't remember: can you help me and show me these posts? Of course they still are here. I don't post that much so they should be easy to find for you. Please do.

Originally Posted by supershaft

Are BMW cam specs valve specs? No one here still knows for sure yet.

If for you it is still not clear, what they are, then behave accordingly. Like it was not clear. Not like your point of view was the only one worth thinking about. That's all I wanted.

Originally Posted by supershaft

At least now you know what the lift check point is and that there is a difference between valve timing and cam timing with our engines and why most smart tuners stick with cam timing. Even why most timing specs regarding OHV engines that are labeled as cam specs are in fact cam specs versus valve specs. Valve specs or cam specs, at least BMW gives a lift check point with their specs so you can actually use them. Those reported variations? Are the variations the cam or the rocker arms?

Now to your lift point. Working with Schleicher cams I never cared about. In fact you didn't yourself with the 336. I did learn a bit about that from you, that is true.
I described how I check that the cam is mounted in the correct position to the crank. I don't need a check point for that.
And I didn't care for more.
So stays your final statement (in the cam thread) that the check point is needed for checking the grind:
Believing that you can check the grind of a complex profile by measuring four points seems to me to be a very optimistic approach.

Do you believe you tought me the difference between valve or cam specs ? Sorry, but that is ridiculous.

Those reported variation? What do you mean by that? The variations in the measurement data?

Now, obviously you regard my posts as destructive. I would appreciate an open discussion about these topics. But open discussion means that differing opinions will be respected, if there are no facts.
And sorry but, the only facts in this thread came from me.

[chasbmw]

Another useful web site:

http://www.rbracing-rsr.com/camshaft.html

[tofgasp]

Thanks for the link, the dynamic compression calculator will be very usefull to choose a cam for the big bore/short stroke I'm currently building.

[DoktorT]

Originally Posted by Max Headroom

Billy, you've missed the clues given by every engine manufacturer for generations including BMW, when they give cam specs. The usual information given is valve timing specs, along with total valve lift. The term "cam timing" refers to the drive from the crankshaft to the cam, and the relationship between the two.

The cam is primarily there to open and close valves at the pre-determined times, when it's not operating an oil pump or ignition system. This data is based on standard rocker arms, for one thing. A change to the rocker ratio is outside the parameters of factory timing specs.

All cams have specs arrived at by using a degree wheel on the crank to determine the crankshaft position when the inlet valve opens and closes, and when the exhaust valve opens and closes. NOT when the rocker arm, pushrod or cam follower moves.

The 2mm checkpoint is partly to get the cam lobes away from the opening and closing ramps, and partly to avoid valves tangling with pistons.

Valve timing has everything to do with the opening and closing of the valves relative to the crankshaft, therefore it is critical to know the correct check clearance (2mm in the case of an airhead) and the exact crank angle when the valves open and close.

Correct me if I'm wrong but it's my understanding that an increase in the rocker arm ratio would affect valve lift rather than valve timing, using the same check clearance. Any change in valve timing would be minimal..

YMMV etc

Very much spot on, and correct in every detail, despite "Damned Human Egos Rampant on the Idiotnet!"