Roller rocker arms
Roller rocker arms
(OP)
Hi guys!
Can you tell me something about roller rockers? Is there any benefits between original rocker arms and roller rocker arms if stay on same arm ratio? I wondering how much influence does to the friction losses? Is there any benefits if i use lighter roller rocker?
Thank you for ideas
Radek
Can you tell me something about roller rockers? Is there any benefits between original rocker arms and roller rocker arms if stay on same arm ratio? I wondering how much influence does to the friction losses? Is there any benefits if i use lighter roller rocker?
Thank you for ideas
Radek





RE: Roller rocker arms
Again than you
RE: Roller rocker arms
RE: Roller rocker arms
I must direct my question to debunk. I talking about low stroke OHV engine.
RE: Roller rocker arms
What you should get, with rocker arms of the same ratio, is better valve guide life. If that's not a problem now, e.g. because you throw away the heads for other reasons with few miles on them, roller rockers may be a waste of money.
Mike Halloran
Pembroke Pines, FL, USA
RE: Roller rocker arms
Can you be more specific in what you mean by an OHV "roller rocker"? Do you mean a rolling element (needle) bearing at the fulcrum? A roller at the contact with the valve tip? Or both?
A needle bearing at the fulcrum does not really provide much benefit over a well designed plain bearing in terms of friction. A needle bearing does not work well with the high-frequency oscillatory motion occurring at the rocker fulcrum. There tends to be a fair amount of roller skidding (and friction) when the rocker rotation stops and reverses direction. The plain bearing has the advantage of lower mass/inertia, and also results in a stiffer installation.
A roller at the tip adds a bit of mass, but it also reduces friction and reduces side loading on the valve stem.
Regards,
Terry
RE: Roller rocker arms
Yes you're right! I talking about "roller at the tip". For clarification here is some pictures, original vs. custom. What is the influence of weight and the material and arm stiffness ?Thanks for your opinion!
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-...
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-...
RE: Roller rocker arms
... but at high rpm in a pushrod engine, everything is a spring, so the dynamics can get complicated enough that rules of thumb will not predict what's going to happen.
Let's back up a bit.
Are you trying to solve a specific problem that's been bothering your engine, or
are you just trying to go faster?
Mike Halloran
Pembroke Pines, FL, USA
RE: Roller rocker arms
Thanks
Radek
RE: Roller rocker arms
There's your answer.
I wouldn't bother unless the stock rockers are a problem.
How many have you broken so far?
Mike Halloran
Pembroke Pines, FL, USA
RE: Roller rocker arms
Thank you very much!
Radek
RE: Roller rocker arms
As for saying (guessing?) whether you'll need them- I'd want to know how much increase in valve spring force you'll need to spin it to 8,000 RPM.
RE: Roller rocker arms
The "built" versions of those engines that I'm aware of (and certainly there could be others) only spin to 7000 rpm and that's limited by the bottom end staying together. If you operate it near the critical speed of the crankshaft assembly, it's going to go boom.