Closed/Open Valve Spring Pressure for .510/.521
02-02-2005, 12:30 AM
#1
Closed/Open Valve Spring Pressure for .510/.521 I need to know more than the basics of valve spring pressure for aftermarket cams
I have a 203/208 .510/.521 with hotcam springs.( Its a stock cam but on 1.7RR) They are rated at .525 but no spring has a lift rating. It all depends on the installed height an spring pressure.
I need to know if the hotcam shims are the same as stock 94Z shims??
Also i need to know at what installed height, what spring pressure is desired for the current cam i am running(.510/.521). Closed and Open pressure.
Installed height is 1.78"( i think, thats what the book says, but not sure on what spring pressure b/c of the increased lift(1.5RR to 1.7RR))
The rockers are 1/2 turn past 0 lash. The car runs good, but falls off hard on the top end. I think it might be b/c of some valve float? I know the guys that have good setups know what they are doing( setting up springs). They just dont buy off the shelf springs and put on the ones that say good to .600 lift with a .595 cam.NOTE( For reasons that i dont know, Gm runs a .525 cam with a .525 rated spring, not sure what installed height and seat pressures)
I am looking for more detailed answers to these simple questions
What seat pressures(open/close),installed height are needed for my .510/.521 lift cam
I have a 203/208 .510/.521 with hotcam springs.( Its a stock cam but on 1.7RR) They are rated at .525 but no spring has a lift rating. It all depends on the installed height an spring pressure.
I need to know if the hotcam shims are the same as stock 94Z shims??
Also i need to know at what installed height, what spring pressure is desired for the current cam i am running(.510/.521). Closed and Open pressure.
Installed height is 1.78"( i think, thats what the book says, but not sure on what spring pressure b/c of the increased lift(1.5RR to 1.7RR))
The rockers are 1/2 turn past 0 lash. The car runs good, but falls off hard on the top end. I think it might be b/c of some valve float? I know the guys that have good setups know what they are doing( setting up springs). They just dont buy off the shelf springs and put on the ones that say good to .600 lift with a .595 cam.NOTE( For reasons that i dont know, Gm runs a .525 cam with a .525 rated spring, not sure what installed height and seat pressures)
I am looking for more detailed answers to these simple questions
What seat pressures(open/close),installed height are needed for my .510/.521 lift cam
02-02-2005, 04:28 AM
#2
The spring you need depends on how steep the ramps are as well. Sounds like you need a set of Comp 918's. You can use these springs up to their full rating of .600" lift. You said you have 1.7 rockers; that is stock, did you mean 1.8 rockers?
A stock cam like that is going to fall off on the high end; it doesn't have enough duration. High ratio rockers mostly increase the lift, not duration.
A stock cam like that is going to fall off on the high end; it doesn't have enough duration. High ratio rockers mostly increase the lift, not duration.
