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grumpyvette · 12-05-2008, 04:49 PM

HEY GRUMPYVETTE?
How much lift can these springs handle? I've read two different things from different sources....One says they can handle .490 another says they can handle .550....What's the real deal? See links below...I appreciate any help rendered.

http://www.motorpartscentral.com/Pro...ctModelId=7726

http://www.trifive.com/forums/showth...ghlight=RV943X

you might want to keep in mind theres differances in the way max lift is being measured in some cases.
example
heres a chart and springs IVE USED

http://www.racingsprings.com/PDF/beehive.pdf

lets look at the last spring on the chart, #PAC 1520

its installed height is 1.880

coil bind is at 1.210
subtract 1.210 from 1,880 and you get .670, yet,its max lift is listed at .650, ok,
but any engine builder will tell you you really need a minimum of .050 clearance, before reaching coil bind, so the real max lift at this point is not .650 but .620 lift, AHHHH!
but thats ONLY if the valve train allows you that .620 clearance, if the valve guides,piston to valve,retainer to valve guide, or valve seals, rocker slot clearance or a dozen or more other factors are taken into account and clearances meassured, youll be lucky in the real world to see that .620 lift clearance, you might have only .590 quite easily, and require either more machine work, or differant retainers, valve keepers etc. to get even that .620 let alone the .650 listed, and yes you can get that .650 but it might require a few tweaks, machine work, and a differant installed height, etc.
I think what they are saying is , that if you just pull the old springs and install the new ones .490 is usually what youll see, do some machine work and check clearances carefully and in theory you get the larger figure.

12-05-2008, 04:49 PM	#1
grumpyvette retired mech engineer Join Date: Sep 2007 Location: florida Posts: 159 Name :	valve spring clearance HEY GRUMPYVETTE? How much lift can these springs handle? I've read two different things from different sources....One says they can handle .490 another says they can handle .550....What's the real deal? See links below...I appreciate any help rendered. http://www.motorpartscentral.com/Pro...ctModelId=7726 http://www.trifive.com/forums/showth...ghlight=RV943X you might want to keep in mind theres differances in the way max lift is being measured in some cases. example heres a chart and springs IVE USED http://www.racingsprings.com/PDF/beehive.pdf lets look at the last spring on the chart, #PAC 1520 its installed height is 1.880 coil bind is at 1.210 subtract 1.210 from 1,880 and you get .670, yet,its max lift is listed at .650, ok, but any engine builder will tell you you really need a minimum of .050 clearance, before reaching coil bind, so the real max lift at this point is not .650 but .620 lift, AHHHH! but thats ONLY if the valve train allows you that .620 clearance, if the valve guides,piston to valve,retainer to valve guide, or valve seals, rocker slot clearance or a dozen or more other factors are taken into account and clearances meassured, youll be lucky in the real world to see that .620 lift clearance, you might have only .590 quite easily, and require either more machine work, or differant retainers, valve keepers etc. to get even that .620 let alone the .650 listed, and yes you can get that .650 but it might require a few tweaks, machine work, and a differant installed height, etc. I think what they are saying is , that if you just pull the old springs and install the new ones .490 is usually what youll see, do some machine work and check clearances carefully and in theory you get the larger figure.