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Old 12-26-2012, 11:05 AM   #31
supershaft
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Quote:
Originally Posted by Voltaire View Post
I've been reading this thread as my R90 racebike has a copy of the 336 cam made by a local reputable cam company.
It goes well for a bike with a motor that cost $250 that although has been pulled apart, new rings/bearings fitted, guides relined and a few minor mods is still running the original 1973 pistons and valves..... had a good season on it, 20 odd races and only one DNF.
I don't know what power it turns out or what the compression ratio is .....hey SS is there any room under your rock.....

I did a build thread on it ..... http://advrider.com/forums/showthread.php?t=790873
At least we are in good company. I called a German piston manufacturer direct once to find out what CR one of their pistons was since they were advertising the same piston having the same CR for two differently shaped combustion chambers. On the phone in perfect English they told me they were guessing the CR since they didn't have the wherewithall to actually measure all the different models. I have told this story many times over but now is a good time to tell it again.

It seems a lot of us need to get more cam knowledge since everyone I mentioned and then some are all getting very different results from a 336 than what Moorespeed reports. It would be great if what he reports added up with what we have experienced but . . . .
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Old 12-26-2012, 11:10 AM   #32
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Quote:
Originally Posted by chasbmw View Post
This is what started it. "just about everything Moorespeed has said about the 336 newly produced or otherwise sounded like he made it up to me based on my experience with them and other inmates experience with them as well. Can't see why .........
That isn't personal other than mentioning sources. That comment is about what Moorespeed said he experienced with 336 CAMS versus what some of us here have said we experienced with 336 CAMS and a direct response to a comment RG made.

supershaft screwed with this post 12-26-2012 at 11:16 AM
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Old 12-26-2012, 11:17 AM   #33
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Quote:
Originally Posted by Rob Farmer View Post
I'm probably showing my ignoroance of cam design here but since the cam followers are off set from the centre of the cams wouldn't the followers spin anyway? I'm not sure why you'd need a taper on the cam face. I've just had a look on three used cams I have laying about and all three have a larger worn contact area marked on the exhaust valves than the inlets but all four lobes on all of them have wear marks supporting the cam followers spinning.
Yeah, that's what I thought, offset lifters create spin, that's why they're offset....right? Same with the rocker on the top of the valve. You want it a little offset to make the valve spin.

I think my cam had the "butterfly". looked like a stock 308 except for the 247, 336 stamped on the nose and the square pump drive. I'm using the later style cam made for bean cans.
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Old 12-26-2012, 11:28 AM   #34
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Quote:
Originally Posted by mattcfish View Post
Yeah, that's what I thought, offset lifters create spin, that's why they're offset....right? Same with the rocker on the top of the valve. You want it a little offset to make the valve spin.

I think my cam had the "butterfly". looked like a stock 308 except for the 247, 336 stamped on the nose and the square pump drive. I'm using the later style cam made for bean cans.
Apparently they need a little help since all those cams Rob was looking at have a slightly higher on one side cam lobe? So far every cam I have looked at does. Whatever works.
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Old 12-26-2012, 01:42 PM   #35
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Any way to tell on an assembled motor? Will the pushrods spin? Put my cam in over 2 years ago. The used 336 had at least 30,000 on it.
Probably a good one I would imagine. The bearing was completely warn out and had to be replaced. I'm guessing it was at least 10 years old. The ware paterns on the lobes were all the same.
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Old 12-26-2012, 02:21 PM   #36
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Monitor valve lash. That's how I caught a lifter wearing into my 308. I think the push rods do spin.
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Old 12-26-2012, 02:37 PM   #37
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Originally Posted by supershaft View Post
I think the push rods do spin.
Yes they do. The lifters rotate and the rods, too.

But I believe they will always do, even with no taper.
I had used a regrind cam once, it had no taper but, the lifters had been spinning. You could clearly see this on the side (the tube) of the lifters.

Combining convex lifters with a cam with no taper IMHO will result in a point-wise (not line-wise) contact between lifter and cam and thus too much stress for the material.

Tomorrow I'll measure the 336.
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Old 12-26-2012, 03:06 PM   #38
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Originally Posted by RGregor View Post
Yes they do. The lifters rotate and the rods, too.

But I believe they will always do, even with no taper.
I had used a regrind cam once, it had no taper but, the lifters had been spinning. You could clearly see this on the side (the tube) of the lifters.

Combining convex lifters with a cam with no taper IMHO will result in a point-wise (not line-wise) contact between lifter and cam and thus too much stress for the material.

Tomorrow I'll measure the 336.
Oh, so the lifters are tapered? Always thought they were flat. Now everything makes since.
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Old 12-26-2012, 06:56 PM   #39
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The lifter faces have a very mild radius to ensure rotation. You can monitor rotation of the pushrods by drawing a line on the pushrods and runnng the motor with the valve cover off. It's kind of fun to watch, and you also get to watch the the oil delivery.
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Old 12-26-2012, 08:37 PM   #40
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Quote:
Originally Posted by mattcfish View Post
Any way to tell on an assembled motor? Will the pushrods spin? Put my cam in over 2 years ago. The used 336 had at least 30,000 on it.
Probably a good one I would imagine. The bearing was completely warn out and had to be replaced. I'm guessing it was at least 10 years old. The ware paterns on the lobes were all the same.
I don't know for sure, but I've always assumed that the "wavy", "undulating" contact pattern on the cam lobe is a sign that the lobe has the proper taper ground on it and that the lifter is rotating. (???) And is visible when the oil pan is removed.

Or so it was explained to me many years ago. Am I correct?

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Old 12-26-2012, 09:30 PM   #41
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Originally Posted by bmwrench View Post
The lifter faces have a very mild radius to ensure rotation. You can monitor rotation of the pushrods by drawing a line on the pushrods and runnng the motor with the valve cover off. It's kind of fun to watch, and you also get to watch the the oil delivery.
Soooo...

If they aren't really a flat tappet, maybe we don't need much ZDDP in our oil?

Have I just turned this thread into a cam and oil argument ?
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Old 12-26-2012, 10:14 PM   #42
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Originally Posted by mattcfish View Post
Oh, so the lifters are tapered? Always thought they were flat. Now everything makes since.
Take two lifters and press them together with the "flat" side. Then you'll see it's not flat.
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Old 12-27-2012, 04:44 AM   #43
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Originally Posted by Rob Farmer View Post
I'm probably showing my ignoroance of cam design here but since the cam followers are off set from the centre of the cams wouldn't the followers spin anyway? I'm not sure why you'd need a taper on the cam face. I've just had a look on three used cams I have laying about and all three have a larger worn contact area marked on the exhaust valves than the inlets but all four lobes on all of them have wear marks supporting the cam followers spinning.

In Ludwig Apfelbeck's book "Wege zum Hochleistungsviertaktmotor" (ways to the high performance four stroke engine) I found the following:
Page 76, concerning flat base lifters: "If the lifter has a small offset to the lobe it will rotate continuously and its surface will wear evenly"
(Wenn er aussermittig zum Nocken angeordnet ist, dreht er sich dauernd, und seine Laufflaeche nuetzt sich gleichmaessig ab).

Page 78: In some low-performance engines lifters may have a large offset to the middle of the lobe so that they slide less and perform more of a rolling motion. The lobe has to have a minimal taper then and the lifter has to be slightly convex. Therewith higher durability is reached. For racing engines this arrangement is not to be considered.
(Nockenstoessel werden bei manchen Gebrauchsmotoren sehr weit aus der Nockenmitte versetzt, damit sie mehr abrollen und weniger gleiten. Dic Nockenlaufbahn wird dann minimal konisch und die Stoesselgleitflaeche schwach ballig ausgefuehrt. Damit wird eine laengere Lebensdauer erreicht. Fuer Rennmotoren kommt diese Ausfuehrung nicht in Frage).
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Old 12-27-2012, 07:42 AM   #44
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Jog my memory-- it's been 25 years since I've been into a VW engine. Are VW (aircooled) engines designed with non-rotating, non-offset, non-convex lifters and cams? I don't recall much of an issue with worn cams and lifters (but then, those parts were replaceable at pocket-change prices) and oil had beaucoup ZDDP back then.

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Old 12-27-2012, 02:41 PM   #45
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Originally Posted by BOETJE View Post
I still have a copy of Ludwig Apfelbeck's book "Wege zum Hochleistungsviertaktmotor" , but it is falling appart. Can you still get new copy's in Germany ?
At least good ones.

Edit: you can get new ones.
http://www.amazon.de/gp/offer-listin...&condition=new

RGregor screwed with this post 12-28-2012 at 05:14 AM
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