Update on the FE Power Cylinder Head Testing

[BigBlueIron]

Amazing stuff!

Rambling thoughts.. Obviously steel would immediately add an immense amount of strength and most likely be the ultimate solution but I believe you could make the aluminum work.

In moving the thrust relief to exhaust you already made a quite a strength improvement not only extending the amount of area for the pivot but just more material.  I don't see the hole for the center bolt being as critical as some. And it would take an even stronger rocker arm to withstand the movement your eliminating with the extra bolt. 

What about adding a rib horizontally along the cross sectional area from the adjuster along the body, kind of like a gusset for lack of term, this would help transfer energy over the offset and add vertical material along length of the barrel area at its weakest point. It looks like there is room for a larger radius on the valve side, maybe not. Just first thing that crossed my mind upon seeing the broken rocker. 

[jayb]

2" of vacuum at RPM, with a huge carb, certainly seems to indicate that the heads are wanting more! Me thinks a tunnel ram is in your future!  You didn't mention intake vacuum with the 8 barrel intake. Was it high also? I would assume it dropped some with the 8 barrel. If not much, then it seems like the heads want more than the intakes can produce. Certainly on that 4 barrel, at least. Were the 8 barrel carbs a known variable? In other words, had they been used successfully on another 8 barrel engine? If so, there has to be a reason they were so pig rich. Vacuum alone shouldn't do that, unless, combined with airflow, it started pulling fuel from places it shouldn't have.

It looks like you have temp probes in each exhaust tube. How were the exhaust temps? That could indicate any issues with intake flow problems (reversion issues with such a big cam, or just a bottleneck?), or any coil/ignition issues, if there are any.

At the risk of sounding like a doofus for missing something obvious, how does that center shaft bolt work? Is the bottom of the intake rocker slotted so that the bolt travels through the rocker, and the rocker pivots over the top of the bolt?

On the intake rocker adjuster; Is there not enough room to move the adjuster over slightly, for additional strength, and modify/machine the intake adapter for some additional pushrod clearance? Maybe there's not enough room around the port to do that?

Okay, sorry for all the questions. Thanks for the great write-up, and it seems like you're only scratching the surface with power production. This is going to get really interesting, as I think you have some real intake development in your future.

I actually didn't run the 8V at any real high engine speeds, but at the lower speeds it did look like it had a lower vacuum than the 4V intake.  The 850 center squirters had not been used before, they were a set I bought from Barry R years ago and had Drew rebuild for me.  So I was starting from scratch on the tuning with those.

Exhaust temps all tracked, but there was some variation, about 150 degrees from low to high.  However, #8 had the bent exhaust valve, and it was highest, so probably some burning was going on in that pipe.

Doug, it's all I can do to restrain myself from making a wise-ass comment about you sounding like a doofus    That center bolt in each rocker pair goes into a post in the steel bar that holds the rocker shafts, picture below.  So the top of the intake rocker has a hole for the bolt to go through when the valves are closed, and the bottom of the rocker has a slot around the post, to allow movement:




On the intake rocker adjuster, it is as far over as it can be without going into the port, while leaving 0.050" of material around the port opening at the lower corner.  In fact on a few of the pushrods I can see interference where they are just brushing the intake adapter at that lower point, so I'm pretty much out of room unless I modify the port.  I'd rather not do that, but we'll see what Joe finds with the flow testing...

[jayb]

Amazing stuff!

Rambling thoughts.. Obviously steel would immediately add an immense amount of strength and most likely be the ultimate solution but I believe you could make the aluminum work.

In moving the thrust relief to exhaust you already made a quite a strength improvement not only extending the amount of area for the pivot but just more material.  I don't see the hole for the center bolt being as critical as some. And it would take an even stronger rocker arm to withstand the movement your eliminating with the extra bolt. 

What about adding a rib horizontally along the cross sectional area from the adjuster along the body, kind of like a gusset for lack of term, this would help transfer energy over the offset and add vertical material along length of the barrel area at its weakest point. It looks like there is room for a larger radius on the valve side, maybe not. Just first thing that crossed my mind upon seeing the broken rocker.

Those are good ideas, and I'm sure I could make some significant improvements to the strength of the design.  But in the end it's still going to be an aluminum rocker, with a fatigue life.  As it was, the original design only lasted about 25,000 cycles (assuming an average of 2000 RPM and 25 minutes of running), and these need to go millions of cycles.  Not sure I can get there with aluminum.  I'll be selling this setup, and frankly I just don't want to offer up a product where I have to make excuses about durability.  This whole cylinder head package is supposed to be about reducing cost to build a high horsepower FE, and if you've got to be replacing rockers periodically that really doesn't fit with the program.

[TomP]

Maybe steel for only the intake rockers? Those are an interesting design, the picture of the lower mounting bar shows the clever way you got that other hold down bolt in there.

Very strange that huge intake and carb still has vacuum at high RPM. That cam is pretty large to peak that low. Could it be something else?

It's quite the accomplishment you have gotten this far and i'm anxious to see it all working as planned.

[jayb]

I think it might be that the cam would pick the engine up at higher speeds, but I really don't want to run this engine any higher than 7500.  Of course, I didn't get there yet, due to the valvetrain issues.  Hopefully next go around I will...

[cjshaker]

Would pairing the shafts on the outer cylinders, and adding caps under the bolts for additional clamping force, be enough to eliminate the center bolts?

I ask, because I would think the termination of the shaft immediately after the end bolts of each shaft provides a significant leverage point against the shaft and bolt. The entire load is taken up by the bolt, in a very focused point. There's enough area in the middle of the head to extend the shafts a bit and use a cap to add clamping force (even if 2 shafts were used, instead of 4). Same goes between the outer cylinders. If the shaft were one piece on the outer adjacent cylinders, a significant amount of force could be added with a center cap, transferring the load over a greater area. The only area where it would be limited to a small cap would be the outer ends. I'd mention a bridged cap in that area, but think you'd run into valve cover clearance issues then.

[Thumperbird]

Fatigue is strength's weakness!
Gotta believe those torsional loads are very high, throw some unknown dynamics in there and who knows.
One can not count on perfect grain structure in those somewhat narrow cross sections.
Regardless of how the failed surfaces look, I highly doubt this is a "fatigue" failure.
Steel!  As others have stated you can likely reduce weight impact by reducing low load area cross section.
Fun and good sport!

[Gaugster]

Werby - The tools have gotten really good.  The problem is that you have to know how to load / constrain the model and interpret the results.  That's where the experience comes in...



It's a powerful thing, but like a 427 Cobra you can drive it wrong and end up in the weeds 

I have a question or rather a concern about the weight of the steel rocker arms vs the original aluminium type. Is the FEA plot you showed intended for steel material? Noting that the aluminium versions are much more bulky in comparison to the plot. I guess I am hoping the weight increase of the steel adds more strength but isn't going to be a lot heavier. Especially at the extremities. (Then Jay will have to add even more bolts to hold down the valve-train.)

[WConley]

Yeah - That FEA image is for the proposed steel version of the intake rocker.  We massaged the design quite a bit to take advantage of the increased static / fatigue strength of the steel.

This is a pretty conservative design, so one could argue that there is still extra pork.  There are lots of unknowns with this new head design.  It's better to test with parts that stay together, and sneak up on a lower weight target if needed. 

Jay's max rpm target is pretty reasonable.  If he wanted to go 9,000 rpm I think we'd be shaving off tenths of grams everywhere!

[frnkeore]

I note that the FEA image doesn't have the c'bore, for the Torrington thrust bearings.

[XR7]

I would think that steel rockers are the direction to go. It looks like they can be strong even with a lot of material removal. I think on these Pontiac steel rockers, they had a 1" offset and the adjuster was on a 5* cant, maybe the cant would help you if you don't have any built in.                                                                                                                                                                                                                                                                                                                   It looks like they did the same as far as a bearing pocket for the side loads on these rockers, you can see the cant toward the pushrod on the adjuster end. Angled toward the pushrod.                                                                                                                                                                                                                                                                                                                                                                                                                                                                       On these rockers, they have the aluminum version next to the steel versions on the same head, you can see how much more material they remove from the steel rocker compared to the aluminum (left and right mirror cylinders, but the same).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                Here is an even bigger offset on a steel rocker for a Hemi I think.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Another steel rocker                                                                                                                                                                                                                                                                                                                         On some high RPM engines I have seen aluminum on the intake and steel on the exhaust, for cylinder pressure, but you could certainly do it the other way around or just go with steel on both.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

[plovett]

Wow!  Great stuff.  Not just the heads, but the story behind them is awesome, too.   I have no advice or even thoughts at this level other than keep it up.   Really, really cool stuff.  Thanks for sharing it with us.

pl

[machoneman]

I would think that steel rockers are the direction to go. It looks like they can be strong even with a lot of material removal. I think on these Pontiac steel rockers, they had a 1" offset and the adjuster was on a 5* cant, maybe the cant would help you if you don't have any built in.                                                                                                                                                                                                                                                                                                                   It looks like they did the same as far as a bearing pocket for the side loads on these rockers, you can see the cant toward the pushrod on the adjuster end. Angled toward the pushrod.                                                                                                                                                                                                                                                                                                                                                                                                                                                                       On these rockers, they have the aluminum version next to the steel versions on the same head, you can see how much more material they remove from the steel rocker compared to the aluminum (left and right mirror cylinders, but the same).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                Here is an even bigger offset on a steel rocker for a Hemi I think.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Another steel rocker                                                                                                                                                                                                                                                                                                                         On some high RPM engines I have seen aluminum on the intake and steel on the exhaust, for cylinder pressure, but you could certainly do it the other way around or just go with steel on both.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Cool pics of all kinds of high performance rockers!

Long ago, IIRC it was Jim Butcher who ran the very last Top Fuel dragster with a BBC engine. Not that competitive with the 426 Hemi-based entries but as the story goes, the engine kept losing exhaust rockers as the forces in a blown nitro engine were pretty fantasic for the stud mount arm. No one at the time made a really strong steel rocker to prevent said breakage as no one else ran a BBC on heavy loads of nitro and high 6-71 blower pressures. Today, a custom-designed rocker would not be such a deal breaker as back then, a supplier needed a ton of orders to justify even a small production run.

[preaction]

Awesome work Jay, it doesnt seem all that long ago you were posting pics of the heads being poured at the foundry.

[jayb]

Thor, thanks a bunch for those pictures, I had not seen those rockers before.  Angling the adjuster was an idea that I had already considered (seen it on some aircraft engines), but it would require an additional machining fixture to get that angle drilled and tapped, so I had gone with the normal straight adjusters on the first rockers.  I was keeping the angled adjuster idea in my back pocket for potential use if there were problems, but at least up to 7000 RPM there doesn't appear to be an issue.

One thing I like about the rockers you pictured is that the roller tip is narrower than what I've been using.  I already have a bunch of those roller tips from my SOHC rocker production, so I used those, but going to a narrower one would help with the weight of the steel rocker.  I'll probably end up going that route.