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Old 01-07-2013, 02:35 PM   #31
pommie john
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Originally Posted by RGregor View Post


Back to timing: of course specs are with respect to the crank. Anything else would be pure nonsense IMO.

Back to the question, how the late 336 are timed. PJ has the numbers? PJ?????


I'm afraid it is so long since I built the engine that I have lost and forgotten the figures!
I have an old piece of paper with some figures that I have written down and these give lobe centres of 95 inlet and 106.5 exhaust, but I cannot be sure where they came from. The opening and closing points I have written down add up to 280 degrees of duration which does not really add up to a sport cam.

I can see that when I have some time, I am going to have to get out the dial gauge and degree wheel and see what's happening inside my engine.
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Old 01-07-2013, 02:51 PM   #32
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Originally Posted by supershaft View Post
I now NEED a rev limiter. Is that curve completely adjustable. So many electronic advances do not have the curve I want. Does the rev limiter cut in all at once or partially?
you can move the curve up and down the vertical lines, Its what I would describe as a 'soft limiter' like a slight miss.
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Old 01-07-2013, 04:24 PM   #33
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Originally Posted by Hookalatch View Post
I have been running my R1200GS cams 9 crank degrees advanced for 5 years and 25,000 miles. Doing so gave me more midrange power (which is what I wanted) with the possible expense of some top end. I rarely go 7,000+ rpm's anyway so I wouldn't notice.

Modern auto engines with variable valve timing, while not Airheads, advance cam timing as much as 7 degrees and retards it up to 45 degrees for a total of 52 degrees variability. Having been involved in drag racing for several decades I am very familiar with the effects of advancing, and in my case more often retarding cam timing to change power characteristics. In my experience cam timing changes of more than 3 degrees are commonly done but usually for reasons other than producing maximum peak horsepower.

Chuck
I didn't say that three degrees was maximum. I said it was the 'classic' amount. It certainly seems to be with BMW and then some from what I have heard and read.
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Old 01-07-2013, 04:27 PM   #34
supershaft
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you can move the curve up and down the vertical lines, Its what I would describe as a 'soft limiter' like a slight miss.
Great! I can't deal with on/off limiters. I could see them making me crash.
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Old 01-07-2013, 04:33 PM   #35
supershaft
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Originally Posted by pommie john View Post
I'm afraid it is so long since I built the engine that I have lost and forgotten the figures!
I have an old piece of paper with some figures that I have written down and these give lobe centres of 95 inlet and 106.5 exhaust, but I cannot be sure where they came from. The opening and closing points I have written down add up to 280 degrees of duration which does not really add up to a sport cam.

I can see that when I have some time, I am going to have to get out the dial gauge and degree wheel and see what's happening inside my engine.
+1! I am going to do it with my spare 336 and a short block if I can figure out a way to get a mid stroke derived TDC. I already have a couple of ideas. I have never had my own degree wheel! I think I am going to get a big one and not worry about timing them in the frame.
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Old 01-07-2013, 04:39 PM   #36
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Originally Posted by supershaft View Post
+1! I am going to do it with my spare 336 and a short block if I can figure out a way to get a mid stroke derived TDC. I already have a couple of ideas. I have never had my own degree wheel! I think I am going to get a big one and not worry about timing them in the frame.


I use a spark plug with the centre electrode smashed out and a bit of rod welded in there. It's maybe 40mm long and although it's not getting positive stop right at mid stroke, it has proved accurate and repeatable, so I'm happy with it.
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Old 01-07-2013, 04:49 PM   #37
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Originally Posted by pommie john View Post
I use a spark plug with the centre electrode smashed out and a bit of rod welded in there. It's maybe 40mm long and although it's not getting positive stop right at mid stroke, it has proved accurate and repeatable, so I'm happy with it.
That's exactly how I would get there too but the engine I want to use is already apart. Mid stroke isn't the important part. Getting away from TDC is! I want to leave the rocker arms out of it at least until I am a bit more familiar with how they usually time although they probably won't make that much of a difference. You never really know until you try it I guess.
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Old 01-07-2013, 07:59 PM   #38
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A lot of semantics being batted around. Of course I know valve timing is measured at the crank. But the cranks are all the same, the cam has been modified ( by moving the key slot back) to produce more advance. The question is...are the later cams advanced 1.5 degree, 3 degrees, or 6? Maybe it really doesn't matter, both cams perform, just at slightly different curves. Last time I checked you could still buy special offset keys from San Jose BMW to make a straight cam advanced or an advanced cam strait. If not, if Mercedes use the same key, they are still readily available on some of the parts sites.
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Old 01-07-2013, 09:05 PM   #39
supershaft
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Originally Posted by mattcfish View Post
A lot of semantics being batted around. Of course I know valve timing is measured at the crank. But the cranks are all the same, the cam has been modified ( by moving the key slot back) to produce more advance. The question is...are the later cams advanced 1.5 degree, 3 degrees, or 6? Maybe it really doesn't matter, both cams perform, just at slightly different curves. Last time I checked you could still buy special offset keys from San Jose BMW to make a straight cam advanced or an advanced cam strait. If not, if Mercedes use the same key, they are still readily available on some of the parts sites.
Since all we can do here is talk about it, yup, it's pretty much semantics. I think what we are saying is that advancing a cam three degrees by MOST everyone's standards is advancing the valve timing three degrees which means three degrees at the crank but none of us knows for sure about the 336. It would be strange if they are in fact advanced six degrees. It doesn't matter at all unless you are timing your cam. Well, except for keeping that intake out of your piston the more it gets advanced. I might look into timing my cam now that I have so much more midrange and bottom end with mine. I can now afford to go looking for a bit more on top but I am going to start that search with the exhaust.

Offset keys. I have bought some Mercedes keys that are suppose to work but they don't fit. The keys I have seen from San Jose were not machined correctly. Not even close! That's pretty much why I haven't timed my cam. It's running good and I don't know where to get any keys to change the timing if I wanted to.

supershaft screwed with this post 01-07-2013 at 09:23 PM
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