SHAFT MOUNTED ROCKER ARMS

Back in the '80s I used allen head bolts on the original TFS BBF heads. There were no stud kits.

Is there any special reason why the stands for the A460's are not machined as one piece? Just curious.

Doug Rahn wrote:Is there any special reason why the stands for the A460's are not machined as one piece? Just curious.

the intake side is,^^pic's.

cool40 wrote:

Doug Rahn wrote:Is there any special reason why the stands for the A460's are not machined as one piece? Just curious.

the intake side is,^^pic's.

I guess I should have stated my question more clearly. Why are the exhaust stands separate from the intake? Surely with the precise CNC machines available today the multiple angles could be accomplished in one piece.

Mr. Gulfstream,

It's a physics problem. With the exhaust ports of an A-460 head towards your belt buckle,,,

The intake rocker stud pad/boss is leaning to the RIGHT. This is it's cant angle of 5* off of the vertical axis. When the head grows due to the coefficient of linear expansion, the intake rocker stud boss grows upwards and to the right in the direction of the cant and incline angles.

The exhaust rocker stud pad/boss is leaning to the LEFT. This is it's cant angle of 5* off of the vetical axis. When the head grows due to the coefficient of linear expansion, the exhaust rocker stud boss grows upwards and to the left, in the direction of the cant and incline angles. Furthermore, due to the additional heat of the exhaust port's bowl, and proximity of the rocker stud pad/boss, it grows at a faster rate than the intake stud pad/boss.

So when the aluminum head heats up, the rocker stud bosses are growing in two different and opposing directions. If we made an entirely one piece stand out of steel, I believe we would create binding forces, that will cause stress and maybe even cracks. IMO we have to design these A-460 stands, sort of like the old SR71 Blackbird. Compensation and adjustments need to be made, in order to allow for the directions that the head grows when it heats up.

I mentioned to Lem the other day, that while this new shaft mounted rocker arm set-up may not be perfect, it is a far cry better than the old set-ups that we had from any of the manufacturers, where we used 16 individual stands. I have the older 16 individual stand set-up on Krisse Lawyer's TFS A-460 headed engine, so I'm speaking from experience.

Charlie

Thanks Charlie, that makes sense. Then it would be prudent not to Tig weld the exhaust stands to the intake?

Doug Rahn wrote:Thanks Charlie, that makes sense. Then it would prudent not to Tig weld the exhaust stands to the intake?

I'd weld it.

Honestly it's debatible and I'm not "leaning" one way or another. I think what we are trying to do here is provide an additional means of holding the exhaust rocker stand down to the head. As Lem mentioned Sunday, there is a helluva lot of lifting force on the exhaust rocker stand. One way TFS has compensated for this problem is to make to exhaust rocker stud bolt hole go much deeper into the head than previously. It's like 1.250" - 1.300" deep on these new BBF3X heads, and I mentioned earlier that we need to use longer ARP 12 pt. stand hold down bolts whenever we can. Also, as anyone understands, a lot of shims under the stands is not good, because you lose threads of engagement.

On Krisse's old style 16 individual stand deal, we tig welded them together when we first built that engine about 3 years ago, however now I have a bunch of cracked welds. One of the problems there, is the different rates (coefficient of linear expansion) between steel and aluminum. Another reason we welded them was to prevent the stands from possibly rotating around with just a single hold down bolt. Now with this new W.W. Engineering set-up, and the intake bar/stand running the full length of the head,,,,,and the exhaust stands butting up against it, there ain't no way it's going to rotate.

So earlier in this thread, I mentioned another option, was to use the right hand exhaust shaft hold down bolt (5/16") to go completely through the steel stand and into the rocker stud pad. At least now with the new heads, we've got room to drill and tap the rocker stud pad. Of course then that stand would be dedicated to that same location every time.

So go whichever way you want to go, furthermore shaft mounted rockers are not for everybody, many people are running just fine using stud mounted rockers and the Jomar stud girdle. As of now, I feel that we've taken two big steps forward in terms of progress. One on the part of TFS to give us these squared up rocker stud bosses and the much deeper rocker stud holes. The other on the part of W.W. to give us these new one piece A-460 rocker arm stands.

Charlie

"On Krisse's old style 16 individual stand deal, we tig welded them together when we first built that engine about 3 years ago, however now I have a bunch of cracked welds."
------------------------------------------------------------------------------------------------------------------------
Thats the virtue of the bar stock stands being all but butted......not having a 'longish' mild steel bridge that under stress will be more likely to crack.

Great discussion and info here guys, Thanks!

I've been thinking about what y'all are saying, and sometimes me thinking can be dangerous, LOL! But when they expand in different directions, which really does makes sense, what is the effect when they are all locked together with a stud girdle?

Doug Rahn wrote:I've been thinking about what y'all are saying, and sometimes me thinking can be dangerous, LOL! But when they expand in different directions, which really does makes sense, what is the effect when they are all locked together with a stud girdle?

The effect is........it's much stronger. The up side in this case is much greater than the downside [if any] .

there is always some play with the thread clearance . (bolt to tap thread) after welding stands , bring engine up to temp and loosen rockers stands and retighten on a hot head . might have to fire up the engine a few times , but expansion/stress could be less done that way for welded or even the one pc. intake stand . Kind of like the hot hone

DanH wrote:there is always some play with the thread clearance . (bolt to tap thread) after welding stands , bring engine up to temp and loosen rockers stands and retighten on a hot head . might have to fire up the engine a few times , but expansion/stress could be less done that way for welded or even the one pc. intake stand . Kind of like the hot hone

Probably a good idea to preheat the stands on the heads prior to welding and cool them down slowly.

Lem Evans wrote:

"On Krisse's old style 16 individual stand deal, we tig welded them together when we first built that engine about 3 years ago, however now I have a bunch of cracked welds."
------------------------------------------------------------------------------------------------------------------------
Thats the virtue of the bar stock stands being all but butted......not having a 'longish' mild steel bridge that under stress will be more likely to crack.

Do you really think the broken welds were due to the difference in expansion direction or could it possibly have something to do with the loading and unloading, flex forces exerted upon them...?

Great information in this post. Thank you Charlie.
When would someone consider switching from stud/rockers to shaft/rockers ?
Would it depend upon the usage ( drag, pulling, road race,street), rpm, HP/torque levels, preference or a combination of all the above?

Thanks,
John

rmcomprandy wrote:

Lem Evans wrote:

"On Krisse's old style 16 individual stand deal, we tig welded them together when we first built that engine about 3 years ago, however now I have a bunch of cracked welds."
------------------------------------------------------------------------------------------------------------------------
Thats the virtue of the bar stock stands being all but butted......not having a 'longish' mild steel bridge that under stress will be more likely to crack.

Do you really think the broken welds were due to the difference in expansion direction or could it possibly have something to do with the loading and unloading, flex forces exerted upon them...?

Probably done cold..... Embrittlement.

"could it possibly have something to do with the loading and unloading, flex forces exerted upon them...?"
---------------------------------------------------------------------------------------------------------------------------------
That's pretty much what I think.

Lem Evans wrote: "could it possibly have something to do with the loading and unloading, flex forces exerted upon them...?"
---------------------------------------------------------------------------------------------------------------------------------
That's pretty much what I think.

Whats Steel is used?

1. Dave, I'll check with Wilfred. I'm pretty sure he does a heat treat after all the machining operations.

2. Randy, you and Lem make a really good point. I'm sure that the loads and the flexing have had a large contribution to the cracked tig welds. I've also had some long discussions with engineers that think because of the cant angles in the bosses being in different directions, we are asking a totally one piece stand to do a conflicting job, with the coefficent of linear expansion being at different rates between steel and alum..

3. John, I think you've pretty much answered your own question. The switch would depend on usage, (such as truck pullers having pulls that last for 18-20 seconds), and of course rpm, valve train weight, and all those other factors.

Charlie

Thank you Charlie. The one thing I didn't realize that would be a contributing factor was valve train weight.

Thanks again,
John

Charlie,

I'm refering to preheat and post heat on welds done on the head to secure the Exhaust stand if its Seperate.

Stress relief of the parts done prior to this is irreleviant to the welding.

lets say a guy had some A460 heads with the stud boss unfinished or even welded some up,then remachined them down flat,like a prifiler or C460.the stands could then be flat and one piece.the ex stand has no cant on it,only the intake,where the stand and head go together.the intake stand could also be machined flat on bottom and reused.maybe even machine the "cant"on the bottom of the ex stand so the welding would'nt cause the two to work against each other.thats a long shot aint it!

So does that mean we no longer have to mill (shorten) the heads studs and in some case the nuts as well for the A460 stuff?

Ace

cool40 wrote: lets say a guy had some A460 heads with the stud boss unfinished or even welded some up,then remachined them down flat,like a prifiler or C460.the stands could then be flat and one piece.the ex stand has no cant on it,only the intake,where the stand and head go together.the intake stand could also be machined flat on bottom and reused.maybe even machine the "cant"on the bottom of the ex stand so the welding would'nt cause the two to work against each other.thats a long shot aint it!

I dont see how that would change that actual angle of the valves...which the rockers would have to be aligned with...soooo.