300° BMW Motorsport cam

['76mintgrün'02]

1 hour ago, kbmb02 said:

  For those who have a #5 camshaft, is this how they are marked?

 

Yes.

 

EDIT, are you going to measure that #5 camshaft?  I've never seen specs posted for them.  All we know is that they are the BEST ones!   

Edited July 31, 2020 by '76mintgrün'02

[jireland2002]

Here you go!    

BMW sport 300 -   duration at .011" lift 300 degrees, duration at .050" lift 240 degrees,  lobe centers 110, lift at valve 10.0mm

These numbers are per an old Metric Mechanic catalog.

We have an original factory cam is stock.  I've been thinking about having a master made and producing them as we now have raw cam blanks.

[markmac]

Old Alpina catalog, large bearing 300, small bearing 300.  Sorry need to convert the PDF to an JPEG.

 

Edited July 31, 2020 by markmac

[AustrianVespaGuy]

On 7/31/2020 at 4:42 PM, jireland2002 said:

duration at .011" lift 300 degrees

Is this the 'standard' way of measuring BMW cam duration, aka duration intake valve is open at least 0.11"/0.3mm? I kinda always assumed they were measured from 0-to-0.  Or do different cam manufactures (BMW/Schrick/etc.) have different lift points from which duration is measured? Because then that would be really confusing. . . sorry always wondered about this and seems a good thread to seek clarification.

Edited August 2, 2020 by AustrianVespaGuy

[TobyB]

Given the long 'advertised' duration, I'd assumed 0.1mm.  But I never really measured anything stock too carefully.

US cam grinders measure at 0.050", thus the advertised duration is much less.

 

10mm of lift is kind of...  not all that much?

 

t

 

[kbmb02]

1 hour ago, TobyB said:

Given the long 'advertised' duration, I'd assumed 0.1mm.  But I never really measured anything stock too carefully.

US cam grinders measure at 0.050", thus the advertised duration is much less.

 

10mm of lift is kind of...  not all that much?

 

t

 

 

Yep, @TobyB (well, according to my notes and measurements, anyway).

 

Schrick cams are measured/advertised duration is at 0.1mm. It’s not easy to accurately measure at 0.004”, notwithstanding at that lift, we’re really talking about the ‘take-up’ ramp, which is not overly important to performance (as typically considered). -KB

[kbmb02]

On 7/31/2020 at 11:48 AM, '76mintgrün'02 said:

 

Yes.

 

EDIT, are you going to measure that #5 camshaft?  I've never seen specs posted for them.  All we know is that they are the BEST ones!   

 

Yes, I’ll measure numbers for the #5 camshaft. 

 

My project is to collect data and develop a grind for a carb-to-exhaust ‘matched component’ performance M10 engine build (*two cam grinds, actually - one for downdraft and one for sidedraft). -KB

[Oldtimerfahrer]

Hi,

I read in the German forum once upon a time that some guys did not want to line bore the heads to take the 300 degree cam and did the reverse... Cannot confirm that. I have a few from old heads, all had large journals. The cam was still available the last time I looked, a new 121 head would not be available though? I bought a new cam one two years ago and put it in an old head that had been line bored but I would think Schrick if I did not have a head to take the big journals.

Andrew

[Son of Marty]

On the hi lift 300' cam like the factory sport cam, I believe that the journal boring was required to allow the cam lobes to pass through the journals without gouging them. Alpina offered a hi lift 300' like the factory cam but they also offered a 300' with less lift and longer duration that didn't require boring the journals. 

[jireland2002]

I just measured the one we have.  It has the larger journals.  Lift at the cam is .310" (7.87mm).  This is just a bit more than Schrick 292 at 7.6mm. 

[Roundeie]

[kbmb02]

On 8/3/2020 at 11:47 AM, Son of Marty said:

On the hi lift 300' cam like the factory sport cam, I believe that the journal boring was required to allow the cam lobes to pass through the journals without gouging them. Alpina offered a hi lift 300' like the factory cam but they also offered a 300' with less lift and longer duration that didn't require boring the journals. 

 

Interesting. And yet, a little odd. Because, if the above is accurate (that is, if both Alpina versions were sold as a “300” (presuming 300 degrees advertised duration), but one version has “less lift and and longer duration” than the other, then one is a “300” and the other is 300 + XX). Marketing?! 

 

On a related note, I have a cam here which is supposed to be a Schrick 316°, but regardless of how I measure, none of Schrick’s specs match the actual unit (lift at lobe, lift at valve, duration).  On my build sheets, I document all cams at 0.050” lift for the sake of comparison. -KB

 

Edited August 6, 2020 by kbmb02

[Einspritz]

I would think that you really need a cam doctor readout to compare.......not just lift and duration.........you are looking for the area under the curve (and then calculating volume of air movement) for each instance of valve movement.

[kbmb02]

Edited August 6, 2020 by kbmb02

[kbmb02]

34 minutes ago, Einspritz said:

I would think that you really need a cam doctor readout to compare.......not just lift and duration.........you are looking for the area under the curve (and then calculating volume of air movement) for each instance of valve movement.

 

Yes, indeed, @Einspritz. I'm using the area under the curve to help develop a couple of cam grinds (with flow data of head / intake(s) / carb(s)). Yet, it not all about what's under the curve, as the absence of clearance ramps on a grind taught recently...

 

To clarify: I collect baseline(+) data while setting cam timing and checking V-to-P, sample below. -KB