Are Stud Rockers inherently a flawed design?

[xr4x4ti]

This an offshoot of my other thread discussing what I should do to safely rev my engine to 7500rpm.

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=54936

As a seasoned mechanical engineer I have never quite understood why stud mounted rockers are the go to method for positioning a valve rocker. The idea of having your pivot point for the rocker floating out in the breeze on a 7/16 pole that is relatively long and not preloaded just seams like a bad idea.

The current darling of the V8 world is the GM LSx family of engines and they went back to a pedestal mounted rocker with a short 5/16 bolt holding them on and they can rev to the moon without much modification.

Without going to a full shaft rocker setup, it seems to me you would want to just have a base that gets shimmed under each valve with a single 7/16 bolt that goes through the rocker and directly into the head. This bolt could then be torqued to preload the whole assembly.

Something like the Yella Terra system seams far superior.



Why isn't that concept more popular?

If the base underneath the rocker is 50% larger in diameter, it would be 5x stiffer in bending.

Unlike a shaft rocker setup it would add very little cost over a regular stud mounted rocker.

Thoughts?

[lefty o]

stud mounted rockers exist for 1 reason $$$$, cheap to produce, and adequate in most cases.

[PackardV8]

When starting down that road, why stop with the pedestal? Would anyone here choose the eight individual pedestals held down with 7/16" bolts over a true single continuous shaft system? Your thoughts on the +/- of each?

jack vines

[Zmechanic]

When starting down that road, why stop with the pedestal? Would anyone here choose the eight individual pedestals held down with 7/16" bolts over a true single continuous shaft system? Your thoughts on the +/- of each?

jack vines

In a perfect world, but that only works in a wedge head with inline valves.

The whole point is to get the pivot point of the rocker as rigid as possible, be it stand mount, pedestal mount, or otherwise.

Now as for what's necessary? Well, there are sprint motors out there now turning 7200rpm+ with 350lb open loads on 3/8" studs with 1.5:1 rockers. It's far from ideal, and done purposefully as one of the efforts to try to limit them. However there are lots of race engines turning far beyond that still using stud rockers and girdles.

If you can, bump up to 7/16" studs. If you think that's not enough, price it out with studs and girdles. You'll probably be within striking distance of a set of shaft rockers. Feature creep yourself until you can't stand to pay anymore, at least that's what I do. Haha.

[86_regal]

stud mounted rockers exist for 1 reason $$$$, cheap to produce, and adequate in most cases.

THIS.

Engineering and design of any system is always constrained by compromise and trade offs.

[ProPower engines]

When starting down that road, why stop with the pedestal? Would anyone here choose the eight individual pedestals held down with 7/16" bolts over a true single continuous shaft system? Your thoughts on the +/- of each?

jack vines

In a perfect world, but that only works in a wedge head with inline valves.

The whole point is to get the pivot point of the rocker as rigid as possible, be it stand mount, pedestal mount, or otherwise.

Now as for what's necessary? Well, there are sprint motors out there now turning 7200rpm+ with 350lb open loads on 3/8" studs with 1.5:1 rockers. It's far from ideal, and done purposefully as one of the efforts to try to limit them. However there are lots of race engines turning far beyond that still using stud rockers and girdles.

If you can, bump up to 7/16" studs. If you think that's not enough, price it out with studs and girdles. You'll probably be within striking distance of a set of shaft rockers. Feature creep yourself until you can't stand to pay anymore, at least that's what I do. Haha.

If I have a choice when using stud mounted rockers I will always go with the 7/16" stud!
Todays manufacturing systems have afforded us the same cost for either a 3/8 stud rocker system or a 7/16" mounting system,
In checking some stud deflection between the 3.8 and 7/16 stud the 3/8 flexed an average of .025 to .035 compared to the larger stud that did not show but .003 flex.

3/8 stud rockers have been an issue since the 70's where a stud girdle was used to keep the studs from flexing and breaking but material and manufacturing techniques have improved 10 fold since then to where the studs and rockers are the same cost for 3/8 or 7/16 making the stud system cheaper then a shaft system.

Yella Terra came up with a good idea but like all shaft mount rocker systems they are twice the money over a stud mounted rocker system and with the availability off set intake rockers most guys go that way rather then the shaft system because of cost. Chevys have the most R+D done for rockers but where a Mopar guy has has the same options there is more cost just because of the engine or head manufacture.
It seems there is alot of ford aftermarket heads use sm blk GM valve train stuff like valves and rockers to keep costs down anyway but the stock head stuff gets specific in alot of cases.

I have used alot of the Crower shaft rocker systems and a few Yella Terra systems but they are by far at least twice the cost of a good stud rocker system. I prefer the Crower shaft rockers over the Yella Terra on sm blks because they have a stronger full length mounting base where the YT and others use individual shafts and 2 bolts through pedestals.
JMO

[midnightbluS10]

Looking over pics of the GM Performance Vortec 4.3L I bought in 2012, it uses the same pedestal type setup and same style of rockers that they use on LS engines, only in 1.5 ratio instead of 1.6:1.

I also noticed that they now use the plastic lifter trays to position the lifters rather than the spider holdown and dogbones from previous years. Not sure when they went to that but it surprised me seeing it in the pics I have. I realize this doesn't really apply to the topic at hand, I just recalled it because LS lifters are so similar.

I often wonder if I could use the LS ratio rockers as an upgrade but haven't really looked into it.

[Walter R. Malik]

They are absolutely great for the job they were originally intended to perform.

[GARY C]

This an offshoot of my other thread discussing what I should do to safely rev my engine to 7500rpm.

https://www.speed-talk.com/forum/viewtopic.php?f=1&t=54936

As a seasoned mechanical engineer I have never quite understood why stud mounted rockers are the go to method for positioning a valve rocker. The idea of having your pivot point for the rocker floating out in the breeze on a 7/16 pole that is relatively long and not preloaded just seams like a bad idea.

The current darling of the V8 world is the GM LSx family of engines and they went back to a pedestal mounted rocker with a short 5/16 bolt holding them on and they can rev to the moon without much modification.

Without going to a full shaft rocker setup, it seems to me you would want to just have a base that gets shimmed under each valve with a single 7/16 bolt that goes through the rocker and directly into the head. This bolt could then be torqued to preload the whole assembly.

Something like the Yella Terra system seams far superior.



Why isn't that concept more popular?

If the base underneath the rocker is 50% larger in diameter, it would be 5x stiffer in bending.

Unlike a shaft rocker setup it would add very little cost over a regular stud mounted rocker.

Thoughts?

If it's set up right the rocker is down on the solid shoulder of the stud not up in the air.

[peejay]

EVERYTHING is an inherently flawed design. The trick is to choose which flaws you are willing to tolerate.

[Geoff2]

The Chrysler Poly head had angled valves.............& had shaft mounted rockers.

[cjperformance]

The Chrysler Poly head had angled valves.............& had shaft mounted rockers.

Only angled in one plane if i remember correctly ?

[peejay]

The Boss 429 had canted valves and shaft mounted rockers. Sixteen shafts!

[PackardV8]

The Chrysler Poly head had angled valves.............& had shaft mounted rockers.

The Boss 429 had canted valves and shaft mounted rockers. Sixteen shafts!

As do millions of production GM LS engines.

[Newold1]

BBC's have always had angled and inclined valve setups and for over 50 years that have been doing just fine with 7/16" studs and stamped ball socket rockers in tons of applications with incredible longevity when run under 5500-6500rpms. When they needed to go to 7500rpms simple stud mount roller trunnion rockers and stud girdles have kept many together inexpensively in countless high performance and racing applications.

When valve lifts, rpms and spring pressures get excessive then the shaft system is the accepted and most reliable way to go. It's just that simple!