Can the 346 big block heads (which I have) be safely milled to a closed chamber shape? Or would they end up too fragile? Seems to me a .100" cut (or more) would be necessary. I've read where people have done it, but many say don't try. Opinions?
You'd do better to just have a set of 516 closed chambers done up. Because by the time you're doen welding you'll have to re-do all the guides and valve job too.
Stroker, milling or pushrod length doesnt affect the geometry on a shaft rocker system. Only the valve job or rocker manufacturing does.
I beg to differ. Unless he spends big bucks on custom length pushrods, and uses adjustable valve gear, it certainly will have an effect. Without either, his engine will likely not even run, and might even cause some engine damage. Also, not to mention that the rocker arms would probably fall right off the valve tip at max lift. Even with adjustable rockers, he would run out of threads on the adjuster on the rockers or come REAL close. Rule of thumb there is only one or two threads exposed. He will need both adjustable valve gear and custom length pushrods to accomplish it correctly. Couple all that with the expense of milling everything and it's pretty senseless. Just my opinion of course.
Look man, I respect you and all, but a chimp could see that when you mill heads, the pushrods are effectively lengthened because the entire head assembly moves closer to the block. Unless he uses custom pushrods and adjustable valve gear, milling .100" off the heads will effect WHERE the rocker tips are in relation to the valve tip. I'm not gettin into a pissin match here, just statin the obvious. with .100" taken from the heads and stock pushrods and valve gear he could end up holdin the valves open on the base circle. I'm sorry, but I have top respectfully disagree here.
Maybe Comp Cams will help.
http://www.compcams.com/Pages/417/valve-train-geometry.aspx
Pushrod length DOES affect valvetrain geometry. Milling heads or blocks on an engine effectively CHANGES the pushrod length.
pppppppppppppYour opinion is all yours...lol. It's wrong, but at least it's your own...lol
Rocker geometry is the sweap of the tip of the rocker over the valve tip. There are only three things that affect that on a shaft rocker system: The length of the valve and seat placement (the valve job); The centerline of the shaft the rockr is rotating around which is fixed unless rocker support blocks are used (meaning factory saddles are milled off); Or the construction of the rocker (meaning the placement of the tip of the rocker in relation to that centerline of the shaft. The gasket surfaces do nothing to help or hinder. And pushrods are only connectors between the lifter and rocker. On a small block pushrods are more of an issue but only because the angles of the pushrod mean really short ones might make the pushrod hit the head at max lift if the pushrod goles are not enlarged. A big block is almost a straight shot. Adjustables are not required but shorter ones will be needed. (Best to get customs and measure for length. On non-shaft rockers that centerline the rocker rotates around becomes a moveable point because the pivots(i.e. Chevy rockers) are moveable on the rocker studs.
If you have adjustable rockers and you Mill your heads .100 why do you need different pushrods??? You have adjustable rockers.
I see this point mentioned all the time ?
With my Crane set-up i could go .200 I think?
Can the 346 big block heads (which I have) be safely milled to a closed chamber shape? Or would they end up too fragile? Seems to me a .100" cut (or more) would be necessary. I've read where people have done it, but many say don't try. Opinions?
Regardless of whether I'm postin in a thread or not, I'm still a suspect. lol I think it's a good idea to find out of it can be done. I mean damn, long as the intake and all is milled to match and different pushrods the right length are used, I would be interested in the outcome. I've always wondered how thick the head deck is and it certainly sounds as if we're about to find out. Course, if somebody wants to rip a old one through a band saw, that'd be cool too.