shoebox

I am not using anything for reference besides my eyballs and feeble brain. If the rocker sits in the same place in either case, what difference will it make how far away it is from the stud boss? Maybe I am missing something, but I just don't see the relevance.

If you look at the diagram I posted earlier, the rocker is "held" in a vertical plane by the pushrod and valve stem. The stud keeps the fulcrum of the rocker in a fixed position relatve to the pushrod and valve stem. If you were to alter only the length of the stud, the rocker would still sit in the same position relative to pushrod and valve stem.

So if the stud base is a little closer to the rocker (as with guideplates) or is a little farther (as without guideplates), what does it really affect? The only thing I can think of would be bending forces on the upper portion of the stud. If the rocker was closer to the base of the stud (as with guideplates), I would think it would resist bending forces even more (stronger).

I'm not a professional engineer. No arguement, just describing the way I see it.

94formulabz

Could you please copy those sections for those of us without the books? Although it would be nice to machine them down to keep the stud in the original location and with the intended amount of thread engagement to the head, i don't think that is critical.

As long as you have enough thread on the stud you are just going to turn the polylock down additional rotations till the rocker has been pushed down to same location as without the guideplates. You have one degree of freedom with the rocker, vertical movement. Since the pushrod and valvestem are in the exact same locations how could you possibly achieve zero lash by adjusting the rocker without it being in the same position.

I definitly don't see how you are effecting geometry in the lashed position. stud location, yes. thread engagement of the stud to the head, yes. but rocker geometry no, you are just holding the rocker furthur down on the stud via additional threading of the locknut the thickness of the guideplate.


-brent

arnie

If you have you ever assembled a top end of an engine, you'd understand where 'Shoe' is coming from. Books are great, but not as effective in gaining experience as actually doing it. The issue here is rocker to stud nut and/or stud radius interference. Either there is interference, or there isn't.

ACE1252

I'm no engine expert, but I think Shoe is right. From what I understand, the roller rocker does not "bottom out" on the stud. This means that when the engine is on, the valve and the pushrod are pushing rocker against the locknut on the stud. This is where you compensate for the additional thickness of the guide plate. Since you are not physically bottoming out the rocker on a non-guide plate valve train, when you add them there is enough stud to allow for you turn the nut a couple of additional turns to "compensate" for the additional thickness of the guide plate. Right?

GA93FORMULA

I know where Shoe is coming from Arnie. I build all of my own engines, plus the engines and rearends of my friends, their friends, family, etc.. I also do my own cylinder head porting and chassis fabrication. Valvetrains are of special interest to me (and others) and I have personally spent countless hours assembling and modifying small blocks. Books written by automotive engineers who specialize (and teach) race engine building are out there for those who want to increase their knowledge of the advanced technical issues regarding valvetrains, cams, etc.. Yeah, experience is a great teacher, but I would rather not make unnecessary mistakes due to lack of knowledge. I have learned in the past that learning solely by experience can get quite expensive (i.e. bent pushrods, broken springs & rocker studs, , and grenaded blocks). Since I am just a poor southern boy, I cant afford to be throwing away my hard earned money needlessly!!! I never said that an LT1 would not run without machining for guideplates. Machining is recommended for proper geometry and proper rocker trunion clearance. Those fellows who feel engineers like J. Lingenfelter and David Vizard are just full of **** should by all means ignore their advice (feel free to assemble your heads/valvetrain any way you desire).

llafro

Put it this way. I have guideplates without any modifications to the mounting points on the heads. It is not a problem. There have to be hundreds of people here that have the same setup with no problems. As with any setup, you have to check with a pushrod length checker that the geometry is correct. The only thing you would change if it weren't would be the length of the pushrod.

That said, there are some applications where installation of guideplates would cause things to be out of whack. One example is the factory roller rockers on a stock LT4. In that case, the rockers are supposed to be torqued down against the studs. Another example would be Ford's pedastal-mounted rockers as used on some 302 engines.

BRAD

arnie

The height of the stud has NOTHING....NADDA...to do with the rocker to stem geometry. Barring interference, the stud does not locate the height of the pivot point. That is determined by the height of the valve stem, and the length of the push rod. This coming from a person that has 'harped' on correct valvetrain geometry here, in the past. Those of us that have mocked up engine assemblies can readily see this. To each his/her own, and be satisfied with the choice/decision. I can leave this thread knowing I tried. FWIW, I have little problem with engineering. It's how it is conveyed in print, where I have the problem.