There, finally found an article with some real dyno numbers.
Gains were minimal at best and only at higher RPM.
http://www.circletrack.com/techartic...son/index.html
Still looking for something legit with Jesel testing, all I find is the same cut/paste propaganda over and over again.
No hard numbers

 

If you are going to rev over 6800, if you have a solid roller cam, or if you heads require an offset type rocker then go with shaftmounts. Otherwise, get 7/16 studs, pro magnum rockers and a stud girdle.

 

+1.

 

I vote for aluminum rockers and 7/16" studs. There has been more than one engine builder that has told me to use the aluminum rocker arms. Depending on the intended rpms you might want to consider a "rev kit".

You notice in the article they did not take the Pro Mags up in the rpm range to try and match the shaft rockers. They used the aluminum.

 

James: look at the scale of that graph. The gain is on the order of 2hp (~0.5%).

Rich

 

That's right, like I said ...

 

To throw in my .2

I think for 90% of engines out there stud mount rockers are fine.. Now if your running a solid roller and reving to the moon shaft mounts can be more of a benifit to the top end by adding more longevity and stability to the valve train, than horsepower gains.. But they you have to figure in the extra cost of the shaft mount and also the added cost of machining the heads for fit. And then they get expensive real fast..

 

doh.

 

jesel sums it up the best, its not always about power adding but preventing power loss due to lack of valvetrain control under situations. the only power addition would be from less friction due to the single plane axis of the design and lack of valve tip scrubbing, this would become more apparent with more radical valvetrain components and spring pressures. all that dyno test shows is that a boat anchor stocker motor doesnt need them with the crap parts its got at such a low rpm and weak valvetrain. almost all race motors use shafts of some kind, theres a reason for it, reliability and control, retaining the power not gaining a bunch. only gains you would see that people are talking about like the 20hp etc. would be from a valvetrain under a loss of control being cured by switching to the shafts and fixing the problem of valve control up top.

1. More Power - Reduced valvetrain friction equals more power, regardless of valve lift or rocker ratio. Shaft rockers are more stable at high rpm ensuring accurate valve timing events. Shaft rockers are mounted to the head using a steel stand that positions the roller directly over the valve tip while the stud rocker is aligned by the stud location and a .080-inch-wall tubular pushrod and guide plate – which one would you rather have in your engine? In many cases the valve, stud and pushrod guide are not actually in line, as found with most small block Chevy intake rockers. This misalignment was generally compensated for in the stamped pivot ball rockers, but became a serious liability to the stud mounted roller rocker as it had no way to correct the misalignment with their single plane trunions.

2. Increased Reliability - Because the longer pivot length rocker does not side-load the valve as much, shaft rockers are easier on valve guides, valve seats and valve tips – fewer comebacks for the engine builder. Shaft rockers simply rotate to take up valve lash – stud rockers slide up and down the stud taking up the valve lash before they open the valve. Example: If your valves are lashed at .030-inch, your stud rocker is sliding up and down the stud every time the valve opens. Just imagine this slide-hammer effect at 7,000rpm! And when valve float occurs, the entire weight of the rocker is loaded onto the valve tip until the system resets.

3. User Friendly - Lashing the valves with stud rockers and the attending stud girdle is a pain in the neck. First, you loosen the stud girdle, lash the valves, and then re-tighten the stud girdle. If the studs are the least bit out of alignment, tightening the stud girdle changes the valve lash. Shaft rockers hold lash much longer and are easier to lash properly. On some vehicles like 5.0 Mustang racecars, the valve covers are very difficult to remove between rounds, so having a vehicle that can go the entire race weekend without adjusting the valves is a big deal. Most racers have found they can remove shaft rockers from their stand to change a valve spring and return them without adjusting the lash again.

4. Additional Benefits - Shaft rockers also offer other features such as; they are more adaptable to constantly changing cylinder heads, they enable pushrod offsets to clear wider ports, and have assorted pivot lengths to accommodate a wide range of ratios, 1.5 thru 2.25!



90% of oem type parts built motors only need stud mount rockers, once you need offset rockers for proper pushrod and port alignment, theres only one true choice for reliability IMO.

 

you dont need to machine a head to fit them, they bolt in using the stud mount holes and use a mounting bar thats adjustable from side to side, then the shaft rockers bolt to the stand.

 

Not true in all cases. T&D does require machining of the guide bosses... not sure about the top-shelf Jesel units. The only setup I know that's truly bolt-on -no machining required- is the Jesel SS.

 

yea, i can see that. its all dependent on what heads are used the stud boss height, and valve lengths. most people have to shim though not remove material, its all in the combination of parts.

 

Any setup I've ever dealt with had to have the rocker arm bosses machined down flat for the shafts to mount on.. But That was on stock casing I'm sure aftermarket heads are more user friendly..

 

Sometimes the point seems to get lost around here.

Point being; unless you know of someone using the same rocker setup, with the same cylinder heads, valve lengths, etc., who didn't need to machine the heads to make them work... great. Otherwise, expect that you may need to have machine work performed. I think that's important point to ponder for anyone hoping to bolt a set on with the heads in the car.