tutorial needed

[ibleedmoparts]

Hey all
Whats the story with roller rocker arms? 1.5, 1.6., 1.7? Just wondering what the advantage/disadvantages were. I always ran stock Ma Mopar stuff but am looking to branch out long as i know the purpose and advantage

 

[MopaR&D]

The different ratios tell how much overall lift at the valve stem will be. Pretty much all rated lifts of cams are the net lift after the most common 1.5:1 rocker ratio is factored in. A higher ratio rocker will give more lift and slightly greater duration at .050" and will also increase the opening and closing speed of the valves. Example: A cam rated at .450" lift will give that much with a 1.5:1 rocker ratio, as the lift at the cam lobe is actually only .300". With a 1.6:1 rocker ratio, the lift at the valve stem goes up to .480 with the same cam (but the duration stays the same for the most part).

Roller rockers reduce the amount of friction at the valve stem by having a roller that rolls (duh) over the tip of the stem instead of just "sliding" on it like stock stamped-steel (and adjustable iron) rockers. At higher lifts the friction becomes more of an issue because the rocker has to rotate through a longer arc and thus has to slide or roll horizontally across the valve stem tip a farther distance.

 

[BJR Racing]

I agree with what your saying until the duration part, correct me if I'm wrong but if you lift the valve further open then close it at a later time doesn't the duration increase? I've found 6-8* more @ .050 depending on the ramp of the cam. I'm just asking?

 

[ramcharger]

I agree with what your saying until the duration part, correct me if I'm wrong but if you lift the valve further open then close it at a later time doesn't the duration increase? I've found 6-8* more @ .050 depending on the ramp of the cam. I'm just asking?

You betcha BJR. Increasing the rocker arm ratio will increase duration @ .050 to a point. As you already know, the amount of duration increase is dependent on the ramp profile.

 

[BJR Racing]

On another note I see V. Gaines is qualified again and a new engine program. Kudos to him! All Mopars are qualified this weekend, hey we even have Dave Connolly in one. We'll get him to a MOPAR eventually once he feels the HEMI's power. JK I'll see Dave in 2 weeks at Atlanta.

 

[ramcharger]

They're racing in Texas this weekend, right?

 

[BJR Racing]

Nope LV, then a week off and then they come here. Steven Chrisman is a uncle of a friend of mine and his son is a co- crew chief on Fast Jack Beckman's car with Johnny West. Joe and I go back to the 90's early 90's, thats Joe Sr. and I. Joe Jr is the co-crew chief. Hey 1 or 2 in's with DSR isn't such a bad deal. But it all comes with time and respect and this go's along way.
As you know it's hard to get in and easy to get out of and harder to keep.

 

[ramcharger]

Nope LV, then a week off and then they come here. Steven Chrisman is a uncle of a friend of mine and his son is a co- crew chief on Fast Jack Beckman's car with Johnny West. Joe and I go back to the 90's early 90's, thats Joe Sr. and I. Joe Jr is the co-crew chief. Hey 1 or 2 in's with DSR isn't such a bad deal. But it all comes with time and respect and this go's along way.
As you know it's hard to get in and easy to get out of and harder to keep.

Very cool!! Respect is given. I hope that I have not stepped any toes? 8) I'm a nobody but lowly bike bracket racer.

 

[ibleedmoparts]

Thanks for the info everyone, so if i was gonna upgrade to new rockers, will the manufacturer have the formula to actually calculate the lift/duration? I really appreciate the info mopekid and BJR

 

[MopaR&D]

I agree with what your saying until the duration part, correct me if I'm wrong but if you lift the valve further open then close it at a later time doesn't the duration increase? I've found 6-8* more @ .050 depending on the ramp of the cam. I'm just asking?

Yeah I agree. It's really just because the valve reaches .050" lift more quickly.