Thread:

Has Anybody run these rockers , Curtisbilt ?

Thanks in advance ........Eric

www.racecurtisbilt.com

It's hard to tell but if they're on individual stands, I'd pass.

Originally Posted by steelcomp

It's hard to tell but if they're on individual stands, I'd pass.

Thanks for the reply Scott , I have a friend that was looking at them , ,, What I see in the pic it looks like they are on individual stands that have a heavy link bolted between them, the adjustment is a cam type at the fulcrum ??? I dont like that but , dont know how well it works . I LIKE MY T&D's ......... E

Ps: Are the Jesels on individual stands ?

I am running a similar set on my 598, it has all of last season on it with no problems, EXCEPT, to get proper rockerarm geometry I had to weld 1/8" plate to the bottom of the stands and mill them to the proper height. Then I pinned them to the head bosses, they say that they will not rotate if just locktited, but I didn't want to chance that. There are so many variations in aftermarket BBC heads and cam base circles, you should expect this. You can't just bolt anything on and expect it to be correct. TIMINATOR

Originally Posted by alkyexpress

Thanks for the reply Scott , I have a friend that was looking at them , ,, What I see in the pic it looks like they are on individual stands that have a heavy link bolted between them, the adjustment is a cam type at the fulcrum ??? I dont like that but , dont know how well it works . I LIKE MY T&D's ......... E

Ps: Are the Jesels on individual stands ?

I run TD's on my BBC they were a touch $$$ initial, I ran the heck out of them they held lash LIKE CRAZY and when they needed to be rebuilt pins and brg's were only about $250...simple job. LOVE 'em and NO WAY the stands could rotate....


Andrew

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Originally Posted by alkyexpress

Thanks for the reply Scott , I have a friend that was looking at them , ,, What I see in the pic it looks like they are on individual stands that have a heavy link bolted between them, the adjustment is a cam type at the fulcrum ??? I dont like that but , dont know how well it works . I LIKE MY T&D's ......... E

Ps: Are the Jesels on individual stands ?

Jessel sportsman are on individual stands with a little link bar. For clarification, I'm not concerned about the individual stands rotating. What bothers me most, and is the biggest enemy of the valve train, is harmonics. I'd rather run stud mount rockers and a good girdle than individual stand shaft rockers. With individual stands, there's no distribution of harmonics. Every stand and rocker is sitting there isolated, taking all the abuse on it's own no matter how well it's bolted down. With shaft rockers, the whole benefit (IMO) is having at least one continuous rocker stand, and the others are bolted directly to it. This distributes the harmonics across the entire head instead of being isolated to each individual rocker pedestal. The same thing occurs with a good stud girdle. Harmonics are distributed and even absorbed to a degree. My guess would be that if you're contemplating a shaft system upgrade, you're turning some decent rpm and have some high spring pressure which makes the need for harmonic distribution even more. I don't think you can do much better than the Jessel, T&D or Crower in 99% of applications with conventional heads. Even some spread ports have one piece stands. Just my opinion, FWIW.

What kind of testing have you done to prove that a one piece bar is better than individual stands?

Originally Posted by steelcomp

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Jessel sportsman are on individual stands with a little link bar. For clarification, I'm not concerned about the individual stands rotating. What bothers me most, and is the biggest enemy of the valve train, is harmonics. I'd rather run stud mount rockers and a good girdle than individual stand shaft rockers. With individual stands, there's no distribution of harmonics. Every stand and rocker is sitting there isolated, taking all the abuse on it's own no matter how well it's bolted down. With shaft rockers, the whole benefit (IMO) is having at least one continuous rocker stand, and the others are bolted directly to it. This distributes the harmonics across the entire head instead of being isolated to each individual rocker pedestal. The same thing occurs with a good stud girdle. Harmonics are distributed and even absorbed to a degree. My guess would be that if you're contemplating a shaft system upgrade, you're turning some decent rpm and have some high spring pressure which makes the need for harmonic distribution even more. I don't think you can do much better than the Jessel, T&D or Crower in 99% of applications with conventional heads. Even some spread ports have one piece stands. Just my opinion, FWIW.

Even individual stands are tied together... they are bolted to the head.

Well I am going to stay with my T&Ds ,

but a friend was looking at these , So I was trying to find out if anyone is running them ,and what there opinion was.

They look like they have some kind of foot that sits on top of the valve stem , and cant tell if it rolls in the rocker or what .

Hey Joey
Have you or a customer run these on a motor, if so what was your opinion of them ? Thanks ..... E

Originally Posted by steelcomp

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Jessel sportsman are on individual stands with a little link bar. For clarification, I'm not concerned about the individual stands rotating. What bothers me most, and is the biggest enemy of the valve train, is harmonics. I'd rather run stud mount rockers and a good girdle than individual stand shaft rockers. With individual stands, there's no distribution of harmonics. Every stand and rocker is sitting there isolated, taking all the abuse on it's own no matter how well it's bolted down. With shaft rockers, the whole benefit (IMO) is having at least one continuous rocker stand, and the others are bolted directly to it. This distributes the harmonics across the entire head instead of being isolated to each individual rocker pedestal. The same thing occurs with a good stud girdle. Harmonics are distributed and even absorbed to a degree. My guess would be that if you're contemplating a shaft system upgrade, you're turning some decent rpm and have some high spring pressure which makes the need for harmonic distribution even more. I don't think you can do much better than the Jessel, T&D or Crower in 99% of applications with conventional heads. Even some spread ports have one piece stands. Just my opinion, FWIW.

I'm going to explain something here and hope that you do not take it as a personal attack. It's not. However, in the past, this hasnt worked out so well, but I'm gonna try anyway. If you research what I post, you'll see what I post is accurate and you'll have an opportunity to learn something new. If you take it as a personal attack/insult, get pissed and attack me, you lose. Regardless, hopefully others will consider the info, do their own research and maybe come away with a more informed way of looking at mechanical systems.
Harmonics is a term frequently and incorrectly used catch phrase used in dynamic systems as a quantity of some force. A harmonic is simply a numeric multiple of a resonant frequency. For example, a resonant frequency of 60 Hz (Hz is cycles per second, multiply it by 60 for cycles per minute) will have "harmonics" at 120 Hz, 180, 240 etc (in engineering refered to as "orders")... Resonant frequencies and their harmonics exist independently in ALL structures. In this discussion, we're talking about rocker arms, push rods, valves, especially springs and the other components.
Resonant frequencies and their harmonics are a function of component geometry, (for the mechanical engineers that had a vibration class, this is simply characterized by the formula of the square root of the stiffness divided by the mass). When a resonant frequency, and/or it's harmonics, is excited, like a bell being rung, it wants to vibrate continuously, drawing energy from the system, and continues to amplify, reaching destructive levels. The only vibration amplitude control for a system operating at it's resonant frequency is damping.
In practical application, a rocker arm/spring/push rod will have it's own resonant frequency. If operated at/or near it's resonant frequency, destabilizing vibration levels develop and typically can result in failures (a common reason for broken springs/bent push rods). To avoid this, you change either the mass, stiffness or damping of the system OR you can change the operating RPM to move the excitation force away from the resonance. As Joey alludes (he's one of the few who's spent time with a spintron and designing rocker arms will probably confirm) having a single shaft doesn't necessarily do anything to change either the frequency or response. The work I've done it modeling/testing the end conditions of how components connect together, I can tell you it actually has NO effect on distributing "harmonics".
Lastly, the subject is of high speed dynamics is so complex, Comp Cams hired a guy with a PHD in mechanical engineering at the same time they got thier spintron. The stuff they were doing was legendary at the time and has led to a better understanding of what goes on in a valve train at high RPM. I wrote a couple articles on the subject, but had to simplify them so much, not sure how much got across. I think there's some vids I think on YouTube of some of the spintron stuff.
The bottom line for the average racer is, if you start having unexplained valve train failures, it's quite possibly resonance related. Unfortunately about all an average builder can do is change operating RPM or to a part with different mass/stiffness, like a thicker wall , larger cross section push rod or a different spring design. Again, harmonics (or more correctly the vibration energy) isn't dissipated through connection points (rocker arm to the bar or push rod tip to rocker arm etc), but only in a change of the part itself...

Originally Posted by GROSERACING

What kind of testing have you done to prove that a one piece bar is better than individual stands?

Must be cool to have your own spintron and actually do this kind of research yourself.... I think I hate you

Originally Posted by TIMINATOR

I am running a similar set on my 598, it has all of last season on it with no problems, EXCEPT, to get proper rockerarm geometry I had to weld 1/8" plate to the bottom of the stands and mill them to the proper height. Then I pinned them to the head bosses, they say that they will not rotate if just locktited, but I didn't want to chance that. There are so many variations in aftermarket BBC heads and cam base circles, you should expect this. You can't just bolt anything on and expect it to be correct. TIMINATOR

Hey Timinator
Sorry I missed your post earlier , Are you running the Curtisbilt rockers ?
the bracket between them would lead me to believe that they would not rotate but I can understand the height issue . ........... E

Originally Posted by David 519

Must be cool to have your own spintron and actually do this kind of research yourself.... I think I hate you

Thanks David for the mechanical eng lesson ,
But have You run these Curtisbilt rockers or know someone that did ? Dammit !!! LOL,,, How you been anyway ????? .......... E

The Curtis rockers seem gimicky to me. I don't see the stirup on the valve being some how superior to a roller. I don't even have that big of a problem with a radius pad on the valve end. M/T rockers had a radius pad as have others.
Don't care for the idea that you cam the rocker fulcrum to adjust the lash. No matter how you slice it, the rocker has to move foward or back while its move up or down for the lash. May not be much, but not ALL the movement can be up or down with a eccentric in the fulcrum.
I have run Jesels, Crowers, and Areospace Components invidual stands and would run any of them over a stud and gurdle deal.

When I win the Calif lottery I am getting a set of these. Or if I get a super killer deal on a set