10-31-2007, 10:38 PM
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Richard Jemison
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Join Date: Apr 2005
Location: Pensacola, Fl. U.S.A.
Posts: 1,443
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Re-Grinding cam cores
 Quote:
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Hey Richard, real quick, if I you were to make your street cam regrinds for a V6, does it matter which camshafts get sent to you - 2.5,3.0,S...?
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It does matter. Two reasons for it.
First is working material to build from. The cam that I show in the website as a regrind is doable on any "normal 2.5" and 3.0 cams. If you have a cam from one of the "164L" series with 9.6mm lift(not all have) there is a bit better intake lobe that can go on it or the "S" as there is a little more material there to work with.
Second is the cam lobe centers, and more importantly lobe separation. With regrinding, lobe centers cannot be changed much if at all, generally not at all. As you know published LCs for 2.5 & non "S" are supposed to be the same, but they are not. Supposedly 2.5/3.0 164 are supposed to be 102/108, & the "S" is supposededly 110.5/108.5. The difference in lobe separation in these cams is 105 and 109.5. What cam you use determines the lobe separation angle and with more upper lobe duration the "S" timing would be better, but not set in the engine to the existing timing marks.
Why Alfa did not use better lobe positions is a result of emission issues.
The "S" intake lobe is only a bit more lift and minor duration increases over the "normal" cams, exhaust is the same. The Intake lobe center is retarded 4.25 degrees on the cam, and the exhaust advanced .25 degree at the cam, compared to the "normal". This movement to increase the length of the power stroke. If you stick the cams in a non "S" head aligning them to the mark on the 3rd journal you will not have optimum timing. You should degree in any set of cams. But without knowing what you have have you can`t set them correctly. In reality in an "S" head advancing the cams 4 degrees will give a better positioning for valve timing to get a bit more power.(to the detriment of emmissions)
Regrinding a set of cams will cost about 2/3 of a custom full or built to specification base circle race or performance cam. (about $450.00 pair for 6 cyl 12 V. regrinds, $700.00 for custom built)
To know what you are getting you must know the full profile of the cam lobes.
Aftermarket regrinds are generally junk. Both profiles on the cam lobes must match intake & exhaust flow characteristics of the motor. If you can`t get the full data on the cams don`t buy them. There is full profiles on my site of "normal" V6 and "S" cams to compare any grind against... There is a link to WebCam as well. Just send your cams there.
It`s past my bedtime!
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Richard Jemison
RJR Racing
http://scuderiagiallo.com
"you don`t have to listen, but you won`t win the argument"!
"Nothing that I might suggest will be legal in California"
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