pushrod length...

[steelcomp]

when useing the term "installed height", what is it being refered to? installed height of the valve stem tip? how can this be changed without useing either longer or shorter valves, and/or grinding the valve stem itself? im sure i am a little confused since i normally refer to installed height with the valve springs, not the actaul valve. obviously valve spring installed height would have no corilation with rocker geometry. so is it common practice to grind valve stem tips? My reference to installed height was really in reference to valve length, which is what I should have said in the first place. You use the lift dimension (among other things) to determin the spring you need, and if you have more lift that a stock spring will allow, then you need a taller spring. The added installed height usually requires a longer valve, but not alwyas, and can be accomplished in other ways. I was referring to excessivly tall springs, which automatically require longer valves, which, in turn, place the tip of the valve closer to the rocker stud, and require the rocker to sit higher, etc. etc.
in trying not to step on Steel's words here, as the push rod gets longer and the rocker sets higher the tip gets closer to the stud, and visa versa. But this is not the way to set up your push rods contrary to what Comp Cams and a lot of others say. Where the tip falls on the valve is the job of the rockers length from the fulcrum to the tip, not the pushrods length. So when you have your pushrod length determined using the method he discribed, the tip falls where the tip is going to fall using that brand(type) rocker.No stepping on my words...that's exactly what I meant. Thanks.
Installed height is the reference to the height of the valve spring in the closed position, so you are right there. There can be variations based on longer or shorter valves. There can also be variations due to the condition of the valve seats. If the seats have been cut a number of times and the valves are "sunk" into the seats further than normal this also affects the installed height, and thus where the tip of the valve is. Now with the tip of the valve being higher due to any number of these reasons, the rocker has to be positioned higher on the stud to get better geometry, thus pushing the roller tip further toward the outside of the valve tip. That happens because the valve angles toward the rocker stud decreasing the distance between the two. Did that make any sense? That's as good a description as it gets.
I think Steel was stating that not to get to concerned with the tip location on the valve and don't try to change it's location by changing the push rod length, it's ludicrous and wrong, there is one correct rod length and has nothing to do with where the tip is located on the valve. That's the job of the rocker/manufExactly. When I bought my Canfields, they had a statement in their tech. description, that their heads were designed using Crane Gold rockers, an installed spring height of 2.0", with a +.100 valve. That was good info.
I'll add this...I don't get too concerned about front to rear location of the roller on the valve tip, because that's pretty much a given, and not much you can do about it. There's a fairly wide margin of error there, but here's the key...as long as you have the correct pushrod length! It's when the pudhrod is too long or too short that the sweep of the roller is much wider, and covers a lot more of the tip of the valve...then you have far less room for error in front to rear location, and it can be a problem. When the pushrod length is correct, the sweep will be at it's minimum, and there's actually room on the tip of the valve for some dimensional or geometrical discreptancies. If the sweep is at it's min., and you still have a gross error in location, then you have issues.
I put far more focus on left to right rocker tip location, because there's something you can do about that, and there really isn't a lot of room for error. When you're seeing open pressures of today's good roller springs, you really need to have that roller centered as best as you can over the valve tip. This is one big advantage of shaft rockers over stud mount (along with many others).
Sorry if I'm rambling on here...but there is a ton of onfo about valve train that most guys don't get exposed to, and to me, it's the most critical part of setting up an engine correctly, and getting the most out of it. I'm hoping this helps.

[jungledave]

ok, stealcomp you wrote me up something a while back that i printed out and I'm pretty sure i understand what your saying but i wanted to get your input as well as others like fiat, gofast, infomatic, and anybody else who knows what they are talking about.
From my understanding to get the perfect length i want to make sure the rocker is 90 degree to the valve stem while at mid lift. To find squareness to the rocker you talked about the trunions (sp) and i'm guessing, because i don't know for sure, that those are the axle type shafts that go through the middle of the rocker and the roller tip. You talked about machining marks and if i understand you correctly i should use the center of these two as a way to align my straight edge and then compare the square end to the the valve stem?
Here's a pic i took, kinda shows what I'm doing..
http://reitanfamily.com/gallery/d/21026-1/DSCF6315.JPG
Another pic, but hard to see valve stem...
http://reitanfamily.com/gallery/d/21038-1/DSCF6319.JPG
Also stealcomp, you talked about pushrod length not having anything to do with where the trip of the rocker is.... The more i extend the adjustable push rod tool the more forward the tip seams to be moving on the rocker.. Also i noticed a few time that the rocker was alittl off to the side of the valve tip, if i release the pressure on the rocker twist it a bit so that the push rod is centered on the guide and not touching one side or the other this is corrected... but whats going to keep things from not moving all over the place, do i have too much play in my guides or maybe this tool is just a bit skinnier than it should be? Now that i think of it there were two sized push rods that could be used 3/8 and 7/16 if i recall correctly, maybe i bought the guides for the beefyer pushrods? Just throwing that out there... i could be making no sense right now Not trying to but in here but I noticed in this months, "chevy high performance magazine" that Dart makes a set of adjsutable big block gide plates. they are a two piece part with an allen screw in t he middle between the two halves but they are $200 a set

[steelcomp]

first your head explodes, then blindness set in
Steel I am impressed, 99.9% of the people out there have this completely jacked up. There is some effect from running longer or shorter rods to effect lift events (sooner or later) but it ends up changing your max lift also and I don't seen any real benefit from it, if you find the need to that just get a differant cam. Also Dart makes an adjustable guide plate because they got fed up when the stuff out being so inconsisdent.There was a discussion on another thread about this where I was being told that the way I describe (not my way, just describing one I agree with) was incorrect, and that there were benefits from what you said above. My thought was that what you're doing, is basically altering cam timing in reference to crank rotation, and if that's benefiting performance, then the cam needs to be re-ground so you're not messing with rocker geometry to get what you need. I liken that to increasing or decreasing PR length to correct roller tip location.
Haven't seen the Dart guide plates. That's cool. I hate aligning rockers.

[steelcomp]

Not trying to but in here but I noticed in this months, "chevy high performance magazine" that Dart makes a set of adjsutable big block gide plates. they are a two piece part with an allen screw in t he middle between the two halves but they are $200 a setDude...that's not butting in...that's great news (although GN mentioned it earlier)...for $200 I'm all over that!
Thanks jungledave

[GofastRacer]

I had to adjust my plates from Comp Cams. They weren't even close, but with alum aftermarket stuff, you never know what's off, and what's right. Bottom line is, the stuff has to line up, whatever it takes.
NO SHORT CUTS!!
Never used Comp stuff, the ones I used were Crower and Crane and both were as close as you could get, at least they were back in the day don't know what the quality is now though. But yeah, regardless it's all got to line up!..

[GofastRacer]

they are $200 a set
Shit that's a deal, you'll have more than that in time cutting and welding stockers!..

[Machinist]

Good write up SteelComp!
That folks is the right way(only way IMO) to setup geometry...

[HONDOG]

Dude...that's not butting in...that's great news (although GN mentioned it earlier)...for $200 I'm all over that!
Thanks jungledave
No need to spend $200. They are in the summit catalog for about $80

[gn7]

ok,
if i release the pressure on the rocker twist it a bit so that the push rod is centered on the guide and not touching one side or the other this is corrected... but whats going to keep things from not moving all over the place, do i have too much play in my guides or maybe this tool is just a bit skinnier than it should be? Now that i think of it there were two sized push rods that could be used 3/8 and 7/16 if i recall correctly, maybe i bought the guides for the beefyer pushrods? Just throwing that out there... i could be making no sense right now
Shaun, don't know why I didn't think of this earlier but all the adjust push rods that I have seen are 5/16 and your guides are most likely 3/8 so this problem should disappear when you get you pushrods. Good luck

[steelcomp]

Shaun, don't know why I didn't think of this earlier but all the adjust push rods that I have seen are 5/16 and your guides are most likely 3/8 so this problem should disappear when you get you pushrods. Good luckThat's true.
Shaun, If you have a set of old PR's, drop an int. and ex. in each hole and go through and check your rocker alignment...you don't need the new ones to do this. -OR- you can wait.
Good write up SteelComp!
That folks is the right way(only way IMO) to setup geometry...Thanks Machnist.