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| Camshaft Identification https://www.ausmini.com/forums/viewtopic.php?f=2&t=98008 |
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| Author: | cooperess [ Thu Nov 29, 2018 3:57 pm ] |
| Post subject: | Camshaft Identification |
Attachment: Mini Cooper 235 Camshaft (1).JPG Attachment: Mini Cooper 235 Camshaft (2).JPG Attachment: Mini Cooper 235 Camshaft (3).JPG I found this camshaft in some Mini parts I bought. Is it special and if so how special. 1/2" lobes, spider drive and 235 etched on the end.
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| Author: | 9YaTaH [ Thu Nov 29, 2018 4:41 pm ] |
| Post subject: | Re: Camshaft Identification |
Here ya go... |
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| Author: | cooperess [ Thu Nov 29, 2018 5:31 pm ] |
| Post subject: | Re: Camshaft Identification |
Thank you 9YaTah |
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| Author: | winabbey [ Fri Nov 30, 2018 3:34 pm ] |
| Post subject: | Re: Camshaft Identification |
Interesting that Waggott's list a Police Pursuit grind (stage 2), and also the 731 (stage 3) that was listed in the BMC SPO41 specification.  Neither the 731 or the standard 1275 Cooper S figures seem to line up with the cam specs in the Special Tuning documentation. Is there an obvious reason for this? |
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| Author: | pfmmini [ Sat Dec 01, 2018 10:02 pm ] |
| Post subject: | Re: Camshaft Identification |
I am pretty sure that the 731 cam, which yours matches, was a rally spec camshaft from the factory. I had one in my Cooper S many years ago and it was a good road cam. Paul M |
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| Author: | winabbey [ Sun Dec 02, 2018 5:55 am ] |
| Post subject: | Re: Camshaft Identification |
pfmmini wrote: I am pretty sure that the 731 cam, which yours matches, was a rally spec camshaft from the factory. I had one in my Cooper S many years ago and it was a good road cam. Paul M Yes, thanks, but I'm basically asking why the specification detailed on the Waggott sheet differs to BMC published figures for at least some of the cams. |
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| Author: | GR [ Sun Dec 02, 2018 6:50 am ] |
| Post subject: | Re: Camshaft Identification |
Hi Doug The reason the figures differ is that Merve took the figures at .012 and .015 where BMC took the figures at .020 the reason being that the Cooper cam has a tappet ramp of.020 to .022 tho, so you can alter the advertised duration depending where you take the reading at, the .050 thou figures are correct and so are the advertised. Graham Russell |
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| Author: | cooperess [ Sun Dec 02, 2018 7:01 am ] |
| Post subject: | Re: Camshaft Identification |
Please explain 'tappet ramp' for the uneducated. |
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| Author: | GR [ Sun Dec 02, 2018 3:58 pm ] |
| Post subject: | Re: Camshaft Identification |
HI Cooperess The tappet ramp is the ramp from the base circle (bottom of the cam) to when the valve starts to open it can be any thing from .002 to .040, the cooper "S" has a ramp of about .022 and the reason for this is that it is very easy on the valve springs, when opening and closing the valve. If you bang the valve open to quickly it sends a shock wave through the spring causing the spring to wobble (harmonics,spring jerk etc) then when it comes back down to close the valve you have to let it down gently on to the seat or it will bounce of the seat , (valve bounce) because the Cooper S did not have a lot of spring pressure they needed to be gentle on the opening and closing hence the long ramp. On one of my race cams the 308 which has fast opening and closing I run a .030 ramp the tappets are set at .028 tho. But we have learned a lot over the years opening them quickly then easing back a little to let the spring get hold of it's self then lay into it. I have just been developing some more road cams that are making race car HP by 6000 rpm to 6500 RPM, but still trying to see what spring pressures I can get away with,it really is a step forward in the development of the A series, we just keep learning more and more about these little motors with cam design and cylinder head design, we have now found a way to get huge flow with a std valve by .350 tho lift just where road cams lift their valve to.  )Graham Russell |
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| Author: | cooperess [ Sun Dec 02, 2018 4:03 pm ] |
| Post subject: | Re: Camshaft Identification |
Excellent explanation Graham. |
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| Author: | Ian_B [ Sun Dec 02, 2018 5:20 pm ] |
| Post subject: | Re: Camshaft Identification |
Is that the advantage of the new generation valve spring that have a tapered form They are not parallel as such .Very good information  Me thinks they are weaker at low lifts and stronger at high lifts and the non uniform shape suppresses unwanted stuff Vizard and Crane did the special cams that were more streetable and outperformed race cams years ago Once they go this way it seems lobes flog out. |
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