Did a ton of searching and nothing obviously directly answered my question. I want to know how long the valve stem is when it is closed, from the valve spring seat to the locking groove. I read a lot about the installed height and what not, and stock is 1.75". Well k-800 lists their spring rate at 1.85", is the stem long enough for that high of an installed height? Also, k-800 springs have a lot of pressure, yet people say they run them on stock heads and do not mention different pushrods. I would think that much pressure would bend the pushrod...no? 135 at 1.75" is a good pressure right? k-800 is 165 at 1.85" so I would think 1.75 would be even more. Also it is almost at 500lbs when compressed. hmmm Need some help here...

 

the final installed height on a spring can be affected by several factors, the thickness of the retainer, the depth of a valve job, and even the thickness of the spring seat. often times you can use a +.050 lock in order to bump the installed hieght of a spring up which will almost certainly mandate the use of an nsa rocker arm due to the "shortening" of the valve tip that protrudes from the lock.

All that being said, in order to find a spring pressure at any installed hieght or any lift for that matter, all you have to do is multiply the spring rate by the lift in inches and add it to the stated spring pressure.

using a k-800 for example,
165lbs @ 1.850"
spring rate (k) = 471lbs

so if you get a height of 1.8" using +.050 locks, the math goes something like this.
471(lbs/in) x .050(in) = 23.55(lbs)
so tack that on the stated pressure at 1.85" and you end up with 188.55(lbs) on seat

the 500lbs when compressed thing... thats if you have right around 700 lift which would open up a whole new bag of snakes wrt to making sure you have clearance everywhere. now with the average lift on this board being about .550" or so on non-custom cams. using the formula from before and a 1.8" installed height you would have 447.6(lbs) over the nose. Which imho is pushing it for a hyd roller cam you're definaitly going to want a pretty stiff pushrod and rocker setup, and a really good lifter on the other end of that. it should be noted a traditional spring will probably lose 20-25lbs after initial breakin (i've seen it and others have reported the same).

imho i probably wouldn't run a k800 spring if i couldnt hit the recommended installed height. my suggestion would be to run a beehive (i know thats what everyone says). i will offer what i've seen both on the dyno and checking the springs after some time on engines. i've had back to back runs with marine big blocks and went into float with a spring similar to the k800 around 5700 rpms, with the beehives the engine ran up to 6500 rpms which was as high as the owner would agree to test. after about 100 hours in the boat doing various poker runs and getting beat on pretty hard the spring loss was minimal(my figures are at the shop or i would state them).

i hope that covers everything, and that i made no math mistakes.

 

Good post.

 

Thanks, that clears a lot up. Now one other one, the max installed height possible on a stock head is 1.8"?? if you did 10* stuff, so stock with 7* is 1.75"? Can't get above 1.75 without machining or 10*?

 

.050", .100", and .200" long valves make anything possible.

If you can't change valves, there are +.050 retainers, and +.050 locks

 

I don't think you are asking the right question. You first need to decide on the closed and open pressure you need. The fast that they give the specs for 1.85" doesn't mean you have to install them at that height, unless you want the seat pressure to be 165lbs (in the case of the specs you are quoting).

It sounds like you are planning to reuse the stock valves. This may, or may not, be appropiate. But taking the stock valves as a given, you should measure them with the stock retainers and seat and get an idea of the maximum installed height for that combo. Then, see if you can find a spring that has the correct seat (and open) pressure for that height. If you need more intalled height, the first step is a retainer or lock that gives you an additional 0.050". If that still isn't enough, you need a different spring or taller valves.

Am I making this clear? The way you have worded the question, it seems like you are trying to solve an equation with two unknowns. You need to pin down two of the three variables and solve for the other. Why the K-800 springs?

Rich

 

Just using k-800 for an example since they seemed to have high rates.

I understand how all that stuff works and installed height can be changed, but simply put; The stock (everything stock on head), max installed height for a spring is 1.75" with 7* and 1.8" with 10* right? To change that you would either need shims to lower the installed height, or longer valves to raise it, or machine work to make the valve sit in further. Correct?

What I was thinking is using stock seats, with 987's, with 7* hardware, with SA rockers. I don't plan on going past 6k.

 

You really should measure it. I still think you are approaching it wrong. FIRST you need to decide what seat and open presure you need along with the amount of lift needed.

Rich

 

don't just assume that because the angle of the lock is different that the installed hieght will vary. and as rich said you need to measure your particular engine depending on the quality of the machine work and tolorences involved you can end up with a great deal of variation on the same head depending on the time invested and the abilities of the machinist.

so a few questions are in order for you i think, what are your goals for the car why the spring change, cam? rockers? if so how agressive is the cam going to be and what rocker ratio?

 

I am just not seeing how the valve height can go greater than 1.8" if EVERYTHING ON THE HEAD IS STOCK. Means, no machining and stock valves. I can understand how it can go lower to 1.6" or something, but that is my question. I cannot go higher than 1.8" MAX with completely stock heads correct? Yes I know I need 10* stuff for another .05.

 

thats correct, you're not likely to achieve greater than 1.8" on a stock head. and if you do the tip that protrudes from the lock will likely not be sufficient for a self aligning rocker arm. the only way to go longer after that is to put in a +.100 valve or more if you need it. however just because a spring manufacturer rates a spring at 1.85 has nothing to do with where it can be installed at and run properly as long as the pressures are in line with your app.

 

That sounds about right, but you have to measure to be sure!!!!!

Rich

 

take it easy Rich or you'll bust a spring

 

OK, OK. I'll take a chill pill.

Rich

 

I know. I will, just meant "theoretically" .