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mark '87 930's Avatar
 
Join Date: Feb 2006
Location: Toronto, Ontario
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sc cam grind? How can you tell by looking measuring?

I wanted to confirm a set of SC cams I received today. How can I tell?
I ask simply because I thought the lobs themselves would be slightly taller (1/10 of an inch roughly) according to the specs I've seen on valve lift figures on drcamshafts.com (.368"/.339" =stock vs .450"/.395"=sc grind). I did a quick measurement and the SC cams I received at vs my stock ones I pulled out ofthe car and my stock ones have 'taller' lobes? I made sure I had the and lowest point on the lobes and measured (with calipers). Wouldn't that give me less valve lift?


How can I tell?
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1987 930
1956 Chevy 3100
2009 Subaru Forester
2003 KX250 X2(I like my toys!!)
Old 01-12-2010, 02:49 PM
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Any part numbers or markings? I had DR regrind mine, and the ends came back stamped "SC" where before they were "930"

Are the ones you bought reground from another profile? IIRC, when the cams are reground, they have to reduce the size of the base circle, so while the lobes may look shorter, the relative lift between the base circle and top of the lobe is actually greater.
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Old 01-12-2010, 03:29 PM
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Quote:
Originally Posted by jwasbury View Post
Any part numbers or markings? I had DR regrind mine, and the ends came back stamped "SC" where before they were "930"

Are the ones you bought reground from another profile? IIRC, when the cams are reground, they have to reduce the size of the base circle, so while the lobes may look shorter, the relative lift between the base circle and top of the lobe is actually greater.
Think about how you set your valve lash, on the low end of the base circle where zero lift exists. If that base has been ground down, and you set your lash as normal, then you will end up with more lift when the lobe comes around. From a completely uninformed laymans view, I think you would have to know the difference from the center of the cam shaft to the tip of the top lobe and bottom base circle to figure out what the lift is. Better yet, send the whole sheebang off to a cam dude and have him spin it.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 01-12-2010, 04:59 PM
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I'm such a tool. Of course, the SC stamp on the end of the cam gives it away (still have th e930 stamp on the other side).

Of course, Mark's logic makes perfect sense. I could actually see the difference in the base circle relative to the cam itself (comparing two of the same lobes on stock and SC grind cam)

Thanks all, nothing to see here.. move along.
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1987 930
1956 Chevy 3100
2009 Subaru Forester
2003 KX250 X2(I like my toys!!)
Old 01-12-2010, 05:05 PM
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