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Now onto springs:
There are only a few really pertinent numbers for springs. They are seat pressure at a particular installed height, coil bind height and spring rate.
For example, the Crane 933 springs I am going to use on my 318 project have a seat pressure of 98 lb at 1.700" installed height and spring rate of 328 lb/in. I am going to install them at 1.600" so I have to add the spring rate times the extra compression, in this case it is 328 x 0.100 = 32.8, to the 1.700 seat pressure so now my installed seat pressure is 130.8 lb, perfect for hydraulic roller lifters. Assuming I use a 0.474 lift cam, the open pressure is 130.8 + (0.474 x 328) = 286lb open pressure, in the ballpark for hydraulic roller lifters. Coil bind is 1.08", so 1.08 + .474 + 0.060 = 1.614 which is more than my 1.600 installed height meaning this might not be the spring for the job because one can't run really close to coil bind as it will destroy the spring. In this case I will be saved because my stock rockers come in with less than 1.5 ratio, a 1.45 is more like it, real lift is 0.458 so the springs will have more than the 0.060 minimum clearance between max lift and coil bind.

If you think about it, the same spring can have many different seat pressures depending on installed height, which could explain the different ratings on the same spring.

R.

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Man... i used to know all this stuff... its been a looong time since i had my head in the cam books...

Anyways, so what you're saying is that as long as i can stay further than .060" from coil bind, i can shim the springs i have for a bit more seat pressure?

The 924-16 spring is a dual-spring. With an installed ht ov 1.900", and coil bind at 1.175", that gives me .725" to play with... minus .060", so .665"?

IF i install it at 1.800" (by my handy-dandy Comp catalog here), the 924-16 is now 137lbs... closer to the 150lbs Hughes springs seat at. That also brings the pressure at .500" lift to 311lbs. The Hughes springs are 325lbs at .500" lift. I assume this means my 'new' coil bind is .625"? Since the lift ov the Hughes cam is .518", that still gives me lots ov room.

Am i close? or is the math not so linear in all this...??? I'm just trying to understand the math now.

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