?

 

I believe that the benefits of pedestal mount rockers over stud mount units are typically seen when high (500# plus) spring pressures, high RPM (7500 +), and extreme ratios (1:8 or 1:9) are involved. A rocker arm is nothing more than a lever that transfers and multiplies the motion that is begun by the camshaft. Making that lever more efficient and more stable will pay dividends when the engine is operated at levels exceeding the ability of the stud-mounted rocker systems to maintain their integrity. I guess it comes down to how you plan to use the engine, how much money you want to spend, and how much it's worth to pull off the valve covers to show off your valve train components.

 

Well, Smokey said that anything you can do to increase valvetrain stability is worth HP.

 

A shaft mount rocker has the advantage of stiffness. The stiffer the parts the less deflection in the system. You normally find this as an advantage in setups were the cam lobe is very agressive. I.E. Solid Roller lobes.

Any deflection in the system, thru weak studs, weak rocker arms, weak pushrod will cause the valve not to open as much as the lobe wants it to open, basically keeping it away from the optimum lift curve that the lobe wants. So the stiffer the system the more the valve opens.

So the shaft mount rocker helps take the deflection out of the system by removing the rocker stud.

One reason why high rocker ratios are only found on shaft mounts is because the shaft mounts can handle the increased loads that the rocker ratio puts on the system. A 500lbs spring pressure on a 1.5:1 rocker is 750 lbs on the pushrod end while with a 2.0:1 rocker has 1000 lbs on the pushrod end. It might increase the lift on the valve side of the equation but it also increases the spring pressure on the pushrod side of the system at the same rate.

Hope that helps,

Bret

 

A power secrete most people over look is pushrod technology. I will tell ya this for fact if you can get a big enought diam pushrod that will not deflect and isn't to heavy in return will in fact net you power gains. I know this because I seen it produce results well worth the money for the pushrods on the dyno.

 

Yep, stiff pushrods are very important; the higher the loads the more important. Pushrod loads don't just come from high valve spring pressures. The acceleration of the valve train plays a big part.

Remember F=Ma. Cams with fast accelerations combined with high rpm and high spring pressures lead to some exotic pushrods in high end engines like Cup and Pro Stock. Double tapered shapes, large (1/2 in) diameters and some exotic metals are all used.

There are speciality pushrod manufacturers whose names are not household words to many of us but certainly are to the high-end engine guys.

 

Trend pushrods!

 

About 20 years ago I recall that some company was experimenting with Carbon Fiber pushrods, trying to get light weight and great stiffness.

Anyone know what ever happened with that?

 

Them, too.

 

I ahve always had good luck with Smith Bro's rods. It has been a while. They still build a good one?

Last setup up was 3/8s rod with 720 open Pressure. they worked great...better then the Crane golds that exploded LOL

 

Yep. They got out of the cough drop business and stick pretty much to pushrods.

 

Experience with a sense of humor. That's cool.

 

Question: How do you tell if an engineer is an extrovert?

Answer: He looks at your shoes instead of his own when he talks with you.

Not original, but often true.

 

Fits my engineer friends all too well.

Rich Krause

 

LOL! Here the the Seattle area we have FAR to many Engineers

Oldstroker when was the last time one came in and told us just to fix XXX problem because that is what the book said is wrong?

Many get WAY to confused when you finaly do agree to there terms(just fix what 'I' tell you so you do not rip me off) and then ask them if they would like find the fault that caused the problem to begin with

As many here know Experiance can not be learned in any book

Those who believe it can will be lost until they discover the truth.

One of the best Engineers I ever met never told me he 'was' one