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asphaltgambler asphaltgambler is offline
Still Doin Time
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Join Date: Nov 2004
Location: Nokesville, Va.
Posts: 5,421
With performance cams the ramp acceleration is faster and the valve opening longer (time) coupled with increased total lift. You need a spring that can handle the additional stress. The spring keeps the valve train under control.

MO here is that a slightly higher spring rate ensures that the valves will be where they are supposed to be at high rpms. Stock springs are designed for stock lift, duration and rpms.

Anytime a performance cam profile is installed you know that the driver will rev it more because the engine will now make power at a higher rpm.

I'm using the Supercup grind in my 3.4 build and choose the 'race' spring set-up from John the camgrinder. This may be slight overkill but this engine should make power to @7K rpm. I don't want any valve float or valve to piston contact in case I accidently over-rev it.

His 'race' springs spec @15-20 lbs more closed and @30lbs more at lift than the stock springs. I would consider this increase modest with virtually no trade-off in frictional drag.
'07 Jeep SRT-8 - Hauls groceries and Hauls *ss
'85 Guards Red Targa - F@#king Money Pit
'95 Road King w/117ci - No time to ride, see above
'77 Sportster Pro-Street Drag Bike w/93ci - Sold to collector
'72 Yamaha CS5 200 Twin - Sold to fellow Pelicanite

Last edited by asphaltgambler; 01-23-2005 at 01:48 PM..
Old 01-23-2005, 01:24 PM
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