valve spring pressures
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Logistics Pro
Joined: Aug 2010
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From: Chillicothe
valve spring pressures
So I am looking through my Chilton manual, and I'm trying to figure out the difference between roller cam springs and flat tappet springs. The flat tappets are listed 200psi @ 1.20 inch height, and the rollers are 196-212psi @ 1.36 for intake and 190-210 @ 1.2 for exhaust. Are they the same springs just measured at different heights?
On top of that installed height for the flat tappet 351 and roller 302 are the same @ 1.75-1.8" int and 1.58-1.64" exh....but the flat tappet 302 is 1.68" into and 1.59" exh
Im just trying figure out if they all have e7 heads from the factory why would the installed height be be the same for the roller 302 and 351 flat tappet but different for the 302 flat tappet? Would it stand to reason they used roller springs on the lightning?
On top of that installed height for the flat tappet 351 and roller 302 are the same @ 1.75-1.8" int and 1.58-1.64" exh....but the flat tappet 302 is 1.68" into and 1.59" exh
Im just trying figure out if they all have e7 heads from the factory why would the installed height be be the same for the roller 302 and 351 flat tappet but different for the 302 flat tappet? Would it stand to reason they used roller springs on the lightning?
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
Roller springs are stiffer to control the greater weight of the roller lifters. Using the same spring on a flat tappet 351 would make sense as their longer pushrods are heavier than the shorter 302 rods. And the Lightning's more aggressive cam would call for stiffer springs as well for higher rpm operation
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Logistics Pro
Joined: Aug 2010
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From: Chillicothe
Cool, because I am probably going to go with a factory replacement lightning cam for my 351. The camshaft and lifters for a factory replacement are $120 cheaper than the Crane 444232 with lifters. And I'm not racing this thing its just a driver so I don't see the need for a fancy aftermarket camshaft.
And that means no pricey aftermarket springs stockers will do.
Thanks for the reply!
And that means no pricey aftermarket springs stockers will do.
Thanks for the reply!
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