MX6.com - View Single Post - Maximum lift of custom cams on stock valves/retainers.

**fredio54** · 6-30-05, 16:46

I just measured the movement limits of the inlet and exhaust valves, and this is what i found :

the maximum movement till the stem seal is hit by the retainer is 11mm on the exhaust side, and 11.5 on the inlet side. at these lifts there is room for 19.75mm of spring on the exhaust side, and 20.75 on the inlet. that means that with the vr6 springs which would be needed for a lumpy cam, the lift is limited by spring binding to about 10.75 on the exhaust side.

to exceed these figures, longer valves and thinner solid lifters would be needed. these amounts of lift should be ok for up to around 220hp NA anyway, so only those who are crazy (and require no bottom end) will need more.

my measuring was done with the same dodgy s/s ruler that i measured the springs with, so once again, not entirely accurate(worse this time due to limited visibility). if you are seriously getting cams made measure it again yourself more accurately and tell me and i'll edit this, and give you credit.

for dutch (and other NA fans) enjoy,

Fred.

6-30-05, 16:46	#1 (permalink)
fredio54 Join Date: Aug 2004 Location: Auckland, New Zealand iTrader: (1)	Maximum lift of custom cams on stock valves/retainers. I just measured the movement limits of the inlet and exhaust valves, and this is what i found : the maximum movement till the stem seal is hit by the retainer is 11mm on the exhaust side, and 11.5 on the inlet side. at these lifts there is room for 19.75mm of spring on the exhaust side, and 20.75 on the inlet. that means that with the vr6 springs which would be needed for a lumpy cam, the lift is limited by spring binding to about 10.75 on the exhaust side. to exceed these figures, longer valves and thinner solid lifters would be needed. these amounts of lift should be ok for up to around 220hp NA anyway, so only those who are crazy (and require no bottom end) will need more. my measuring was done with the same dodgy s/s ruler that i measured the springs with, so once again, not entirely accurate(worse this time due to limited visibility). if you are seriously getting cams made measure it again yourself more accurately and tell me and i'll edit this, and give you credit. for dutch (and other NA fans) enjoy, Fred.