reground cams

[tyson 320i/323i]

i am looking to buy a new cam but dont want to shell out almost $500 for a new cam when a regrind is half that price. could someone here help me out

[tommi_e21]

what actually is a reground car exactly???? surely grinding crap off will make it have less lift or do they weld material on and then grind it down???? time for wikipedia me thinks

[Millar]

I believe they take some away, then add some on, then re-profile it

[PeteK]

They don't add any extra metal when they regrind. They grind the zero lift area down and this effectively gives more lobe to play with. Then you can grind the lobe into a new profile. You have to adjust the valve clearance though to take up the gap created by the grinding.

An example is the difference between a high performance Schrick and some other performance cams (like Top End Performance). The Schrick 316 won't fit through the bearing journals because the lobe is too tall. The Top End cam has the same lift and duration, but fits through the bearings. This is because it has a smaller overall lobe. You need to take up the valve clearance with lash caps though.

In the drawing below, you can see the original lift would be B-A and the new lift would be B-X which would be bigger.



There's a limit to how much you can grind off though before you start going through the hardned zone. That's why re-ground cams tend to have more duration and overlap, but not the same big lift as a new cam.

I know Korman used to sell a reground cam with 300 degrees duration and 9.5 mm lift for about $200 vs the Schrick 292 (10 mm lift) for about $500. Korman's stage 2 M10 (apparently) produces 10 more hp if you use the Schrick 292. $30/hp!

I bought a Top End 316 cam (11.5 mm lift) for my M10 for $369. I've not built the engine yet though, so I've got no idea about how it compares to the Schrick.

Cheers

[tyson 320i/323i]

thanks the breakdown of how its done. would really like to know how it works out for you on your rebuild. im most likely gonna go with the top end performance regrind, probably the 284 regrind