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Not all B20 cam blanks are the same ! not the ones I have 120-130

posted by  someone claiming to be Stefan on  Fri May 27 09:26 CST 2005 [RELATED]

Hello,

Today I dug up all the new B20 cams I have in my basement.
I did some comparisons:

Kent cam (well known Englisch brand), the one that failed in my B20:
The diameter of the shaft itself, between the lobes, is 23.5mm
The base circles of the lobes is 25mm total lobe height is 32mm
It has an edged shape cast on the shaft that no other B20 cam has.

An unknown origin performance cam, cast in the shaft is 'Made in UK'
This one seems to be hardchromed, very light grey color.
Diameter of the shaft is 27.3mm
Base circle diameter is 27.5mm and lobe height 35mm

Another unknown origin cam, maybe a regrind, S764 is marked on it.
After timing it , it seemed very similar to the Volvo F-grind.
Made in USA is marked on it
Diameter of the shaft 27.3mm
Base circle diameter 27.4mm , lobe height 34.7mm

A few things that come to mind :

All cores don't (at least back than) come from the same factory.
My Kent cam does probably flex a lot more because of the 3mm slimmer shaft (especially with double valve springs). This was already a problem with the stock diameter shafts when using high lift profiles.

The base circles being 2.5mm smaller in diameter makes the lobes suffer more due to higher accelerations the smaller diameter results to.

I still have to measure my KG6 cam but I fear the base circle is also smaller and the shaft slimmer. GRrrrrrrrrrr !

I compared the timing gear that was on my Kent cam with another steel item I have, the timing marks alligned, so my 8° ofset isn't caused by the cam gear.

Best Regards

Stefan





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