Pro comp cylinder head question

[pw_Tony]

Installed Height is a spring spec, not a valve length spec.
When you buy a set of springs, they are designed to be installed at a certain height. This is the proper height of the spring that will give the correct amount of seat pressure, and is controlled by the length of the valve stem. If the valve is longer than the rated installed height of the spring, there will not be enough seat pressure and your valves won't seal to the seats, causing major compression and valve float issues. If the valve is shorter than the rated installed height of the spring, the spring will apply too much seat pressure to the valve, which will cause the valve to beat the shit out of the seats. It can also cause a flat tappet cam to go flat by making it harder for the cam lobe to open the valve. On a roller cam, too much seat pressure can ruin the roller axles on the lifter, and cause a hydraulic lifter to blead down.
Other issues with having too short of a valve stem will be incorrect valve train geometry and excessive coil bind.
I'm pretty sure you find out your installed height of the valve with retainers first. You can't find out your installed height just from the springs, you need the valves and locks first. Then adjust the spring you're going to use accordingly

[Jetaholic]

I'm pretty sure you find out your installed height of the valve with retainers first. You can't find out your installed height just from the springs, you need the valves and locks first. Then adjust the spring you're going to use accordingly
You're misunderstanding me.
Not to get into a pissing match but...
When the valve is on the seat, the valve spring is slightly compressed so that it can hold the valve up and on its seat so that it can seal itself against the seat. The more you compress this spring the more seat pressure you will have.
A cam manufacturer always recommends a certain spring to be used with a cam. That spring is rated to provide X lbs of seat pressure at a certain height. Take for example the cam card for my cam. The spring is rated to give 135lbs of seat pressure at an installed height of 1.875". This means that with the valve up against its seat, the distance from the bottom of the spring to the top of the retainer is 1.875". The distance from the bottom of the spring cup to the top of the retainer controls this, and this is where the length of the valve stem comes in.
Installed height refers to the recommended height of the spring itself, not the valve.

[pw_Tony]

Exactly, so you get the valves, and find out what springs you need. What kind of cam do you have that needs 135lbs of seat pressure? Is it a solid?

[Jetaholic]

Exactly, so you get the valves, and find out what springs you need. What kind of cam do you have that needs 135lbs of seat pressure? Is it a solid?
No it's a hydraulic flat.
135 lbs seat pressure/395 open pressure
The ramp rates of the lobes are more aggressive, necessitating the need for a stiffer spring. You have to run anti pump up lifters with them because of their stiffness. It's an Isky cam, p/n 396282...it's what they recommend on their cam card and it's what they send when you buy the cam as a kit. They also provide the lifters as well.
Again...that's not how it works. You don't match the springs to the valves, it's the other way around. The cam manufacturer dictates the springs you use with their cam profile based on required seat pressure, spring rate, open pressure, etc etc. Most cam manufacturers will not warranty a cam if you use any spring other than what they recommend you use with their particular cam. You then purchase valves that give you the recommended installed height with that particular spring. The cam manufacturer determines the springs you use, which will dictate your valve stem retainer height.

[fc-pilot]

Again...that's not how it works. You don't match the springs to the valves, it's the other way around. The cam manufacturer dictates the springs you use with their cam profile based on required seat pressure, spring rate, open pressure, etc etc. Most cam manufacturers will not warranty a cam if you use any spring other than what they recommend you use with their particular cam. You then purchase valves that give you the recommended installed height with that particular spring. The cam manufacturer determines the springs you use, not your valve stem length.
Alright, I am not going to say anyone is wrong or right but I will share how I do it. I get the heads and install the recommended valves (as to not screw up the geometry). From there I purchase springs that will work with the cam that I plan on running. I then measure up the installed height with a standard lock and retainer that I have a few spares of. If I need to increase the installed height I then purchase locks and retainers that will give me the measurement that I need. If I have too tall of an installed height I can either buy locks and retainers that will bring it down, or shim the spring up to get the right height.
As a side note I don't think I have ever installed the recommended springs. I find a spring that fits the criteria that I want and go with it. I am a big fan of PSI springs and have more sets of those around the shop than the rest of the brands put together. I am not trying to slam anybody’s stuff, that is just what I have used with success.
Paul

[pw_Tony]

Alright, I am not going to say anyone is wrong or right but I will share how I do it. I get the heads and install the recommended valves (as to not screw up the geometry). From there I purchase springs that will work with the cam that I plan on running. I then measure up the installed height with a standard lock and retainer that I have a few spares of. If I need to increase the installed height I then purchase locks and retainers that will give me the measurement that I need. If I have too tall of an installed height I can either buy locks and retainers that will bring it down, or shim the spring up to get the right height.
As a side note I don't think I have ever installed the recommended springs. I find a spring that fits the criteria that I want and go with it. I am a big fan of PSI springs and have more sets of those around the shop than the rest of the brands put together. I am not trying to slam anybody’s stuff, that is just what I have used with success.
Paul
Exactly springs after height

[Jetaholic]

Exactly springs after height
I see where you're coming from now.
You are correct...the actual length of the valve stem should be selected for proper valve train geometry. If the retainer height of the valve is too long (or you could say the valve tip is too short), you can shim the bottom of the spring to get the correct spring installed height.
However, if the retainer height of the valve is too short, you'll have to go with valves that have the same stem length, but with a shorter tip.

[steelcomp]

Sorry guys, Jetaholic is right. If you're running a big roller with .800 lift, you're not going to run a standard length valve, no matter what the geometry is. This is why there's a choice of valve lengths in teh standard legth (whatever that is) + .100, +.200, or whatever. The added length is to accomodate taller installed height springs which may be required depending on the cam. The geometry issues are definately a factor, and one of the reasons you step up to a performance head. Canfields (and most other performance alum heads) are designed using a .100 long valve. This way when you need a spring with 2" installed height, which is likely if you're stepping up to aluminum heads, you won't have those geometry issues as mentioned.
Originally, on the drawing board, the length of the valve was worked out with everything else in consideration to get the right geometry, but it alone was not the deciding factor. In this case, valve length is dictated by installed height of the spring. Period. If you have to run a long valve and it's causing geometry problems, it's time for better heads. Adjusting installed height with offset retainers isn't really the way to go, but it works in a pinch. Another way is to cut the spring pads, but you have to be careful about getting into water on some hedads. Taking off .050 isn't usually a problem, and a better solution than offset retainers. Offset retainers often cause retainer to rocker interfearance. The valve tip needs to extend far enough above the retainer to allow for full rocker articulation. It might be OK with a 1.4"-1.5" dia. spring, but get into the bigger springs and you're usually going to have problems.
Just my .02

[IMPATIENT 1]

Springs are comp 924-16 installed ht 1.880 Thank you mike
i think you'll find they end up installing at 2.0-2.1 if you use the valve length they tell you too been there, done that. i threw the boxes away for what valves i ran. both ex and in where manley ss. used comp spring comps, comp retainers/locks/lash caps.
they way i set mine up, i can clear a .800 lift cam pretty easily with the length they wanted me to run.

[IMPATIENT 1]

here's a link to some more stuff on the heads:
http://www.superflowheads.com/bbchev.html
same heads, just sold under another name