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?
Milling big block heads?
- Thread starter polkat
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moper
Well-Known Member
They can be cut .100 but it's really costly to get the additional milling done to the intake because you can't mill the intake flange more than about .030 before the valve cover bolt holes get really close to the mating surface. So you end up with a one-engine only fitting intake.
I had a set of BB heads cut alot but not to the point of being closed chambered. I really don't think there is enough material in the deck surface of the head.
moper
Well-Known Member
I dont think .100" will get you to closed chambers either. I think it's more like .150" and I think that would be too much...lol. Just abad idea IMO.
I pretty sure mine were cut .100 and it left about .030-.040 lip of the open chamber. And man It left me with the felling that rthe head was fragile. I ran them for a long time without a problem .
Valve train geometry would be my main concern.
A stupid thought? How about to go the other way around and to have the comustion chamber on a open head filled with a proper materia, to make it a closed chamber?
Still probably cheaper to get a alu head.
Still probably cheaper to get a alu head.
You mean like welding the open chamber area up? Geez. That would really be costly to get done RIGHT. Cast iron can be welded correctly, but it's VERY time consuming to do right. Heat, weld, cool over and over and over and over again. That's the only way.
moper
Well-Known Member
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.
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.
The heads I was talking about were Max wege ported by Dan Dvorak a old factory stock racer for years and is located in Waldo Fl. it really wasn't that big of deal on the rocker/pushrods. I used Hughes 1.6 roller rockers and had custom length push rods. Never had a valve train problem.
moper
Well-Known Member
Your 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.
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.
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.
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.
Me and Moper both have said the same thing on the push rod length. Yes you will need custom/shorter pushrods. And when you take that much off the heads I would think you would plan on Roller rockers also.
Puzackly. But Moper clearly said milling did not affect geometry but it does. It moves the arc that the rocker travels in. Clearly, that is a big effect.
tooslow
Well-Known Member
ppppppppppppp
Getting proper length pushrods after such a milling would be a no brainer. The correct length pushrod is critical and even more so on solid cams. If there wrong, then the geo. goes off. Milling the head dosent effect the geo.
....................There is no geometry difference between B/RB blocks, just a shorter/longer pushrod legnth to make up for the difference in deck height........or if u deck the block alo,same...same................kim........
1wild&crazyguy
Banned
as long as you have the proper thread engagement so many below and above the nut and rocker, otherwise you will need new pushrods.
It's push rod geometry, too much adjuster fiddles the lift.
It's push rod geometry, too much adjuster fiddles the lift.
1wild&crazyguy
Banned
put a stack of feeler gages in the shallow side of the chamber flush w/ deck, then add the stack up, thats how much milling will need to be done.
When you mill the deck into the water jacket you'll know you went too far.
1wild&crazyguy
Banned
/\ too funny.lol
lets try and get along, I see 2 threads that have few usual suspects up in arms.
lets try and get along, I see 2 threads that have few usual suspects up in arms.
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.
1wild&crazyguy
Banned
I have a lonesome 906 head that I'm porting a few ports differently for testing and the rest I'll section with a saw.
stay tuned.
moper
Well-Known Member
I rana set of 516s that I ported and had milled .100" There's a lot of meat there. But, beyond that, I wouldnt bother. As I said, you have to make everything fit after. That engine made plenty of power and was 12:1 when it was all said and done. I can sonic test them now... I'll go get a few numbers at some point and post them. I have 516s, 346s, and 906s downstairs.
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