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drmini in aust
PostPosted: Fri Mar 21, 2014 12:44 pm 
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I have some near new inlet valves here that had Minisport rollers on them, all 4 had a concave radius on the end of the valve stem before I ground them flat.

I'll stick to non-rollers, thanks. :wink:

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Scoop
PostPosted: Sun Apr 20, 2014 11:14 am 
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Has anyone tryed the MED roller rockers? They look pretty good. The price seems good as well.

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MG Rocket
PostPosted: Sun Apr 20, 2014 7:35 pm 
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Chux wrote:
......they mushroom the top of the valves instead! ;-)

I'd be pretty interested to know how this could happen :(
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Chux
PostPosted: Sun Apr 20, 2014 7:55 pm 
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MG Rocket wrote:
Chux wrote:
......they mushroom the top of the valves instead! ;-)

I'd be pretty interested to know how this could happen :(



No idea, all fixed now though and hasn't happened since. Might just have been a suspect valve?

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drmini in aust
PostPosted: Sun Apr 20, 2014 8:18 pm 
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Some valve stems are stellite tipped (=hard) but most are soft.
The contact radius of roller tip rockers is a lot less than that of normal rockers. So, the valve spring load is concentrated in a smaller contact area when the rocker opens the valve. Potential for faster wear/valve stem damage.

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Mick
PostPosted: Tue Apr 22, 2014 3:49 pm 
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Yep, I had this happen to three of eight new valves a couple of years back. The rockers weren't at fault, it was the valves. Lower end Minispares ones, I guess 5/8ths of the time you get what you pay for with low end valves...

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drmini in aust
PostPosted: Wed May 07, 2014 8:32 am 
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I've been told in UK you can buy hardened steel caps to sit over the valves for the rollers to run on.
Not sure if they are for stock 7/32" valve stems, or the 6mm stem race ones...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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smac
PostPosted: Wed May 07, 2014 8:35 am 
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drmini in aust wrote:
I've been told in UK you can buy hardened steel caps to sit over the valves for the rollers to run on.
Not sure if they are for stock 7/32" valve stems, or the 6mm stem race ones...

That's gotta mess with the geometry a bit? (valve height)

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drmini in aust
PostPosted: Wed May 07, 2014 8:37 am 
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Nah you just shim the rockers up.
GR and Minis Plus both sell laser cut shims.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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Scoop
PostPosted: Wed May 07, 2014 8:28 pm 
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How does the cap stay in place? Loctite? Or is there enough of the stem before the collet?

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drmini in aust
PostPosted: Wed May 07, 2014 9:18 pm 
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It sits over the stem and clear of the collet. Same as valve shims on an Alfa etc do.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. :mrgreen:
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MiniBob
PostPosted: Thu May 15, 2014 2:45 pm 
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I found this article.

http://www.racetechmag.com/features-1/l ... stems.html

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