Double-Timing...

[go-fish]

1.6 or 1.7 roller rocker arms.

[nivvy]

Okay, for starters, what does a "1.6/1.7 roller" MEAN?  What is that a measurement of?

I guess I really need to decide if I want the power of a solid or the streetability/lower maintenance of a hydraulic.  I understand what y'all are saying, but I'm still thinking "hydraulic..."

I've got some time to think about it, though.

Thanks, Stroker.

Jeff

okay lets tak the mopar .528 cam. that lift is at 1.5 rocker ratio....... to convert to 1.6/1.7 you use this formula....

.528 / 1.5( rocker ratio) ='s .352 lobe lift.... now multiply the lobe lift .352 * 1.6(rocker ratio) is .563 lift now...
.352 * 1.7 is .598 lift...... now this i before lash setting (gross lift) subtract the cam cards lets say .028 lash setting and you have a "net lift" of .570 ........ hope that made sense...

You can reach higher lifts easilly this way to get in the better flow area of the head.... yet still retain lower duration for better streetability...


StRoKer

[ViperMan]

Ooh, so basically you're extending the left of the cam by using a different rocker.  What is different about the rocker to achieve that?  I mean there has to be an extra "hump" or something somewhere I'd guess, maybe where the pushrod sits?

The .028 lash - that's to compensate for parts expanding under heat, right?  That way you don't bent a push rod.  How do you adjust lash, anyways?  With the rocker shaft design on 440's, how do you adjust lash across the head?  Do aftermarket alum. heads even use rocker shafts?

And how much lift do you want before you start messing up things like scavenging and air/fuel ratio?  I mean, how much lift is too much lift on a streetable engine?

Jeff

[tancuda]

Ooh, so basically you're extending the left of the cam by using a different rocker.  What is different about the rocker to achieve that?

Jeff

The pivot in the rocker is offset to achieve the correct ratio (somebody correct me if I'm wrong)

And here's Hughes engine's site : http://www.hughesengines.com/

You should also find instruction about rocker ratio and valve lash, or go here : http://www.compcams.com/DefaultWide.asp

for technical details.

 

[bb71challenger]

Yes, be smart and get the 3 bolt timing chain and cam 

[nivvy]

Ooh, so basically you're extending the left of the cam by using a different rocker.  What is different about the rocker to achieve that?  I mean there has to be an extra "hump" or something somewhere I'd guess, maybe where the pushrod sits?

The .028 lash - that's to compensate for parts expanding under heat, right?  That way you don't bent a push rod.  How do you adjust lash, anyways?  With the rocker shaft design on 440's, how do you adjust lash across the head?  Do aftermarket alum. heads even use rocker shafts?

And how much lift do you want before you start messing up things like scavenging and air/fuel ratio?  I mean, how much lift is too much lift on a streetable engine?

Jeff

Rocker Install
http://www.cuda-challenger.com/cc/index.php?topic=46346.0

[The Cuda Guy]

Yes, be smart and get the 3 bolt timing chain and cam 

   I have read on here where someones one bolter came loose and messed a whole bunch of stuff up!

Don

[Moparal]

  I have read on here where someones one bolter came loose and messed a whole bunch of stuff up!

Don

That is true. I remember posting in the thread. What a mess. It took his dowel pin off the cam and then just ground everything into powder going all through out his engine as I recall

[bb71challenger]

  I have read on here where someones one bolter came loose and messed a whole bunch of stuff up!

Don

I dont know about the other poor slob but I had a one bolter loosen up on my 400 with a fresh set of 906 heads. It ruined a nice set of stainless valves 2.14/1.81's. It cost about 500 bucks by the time I bought a 3 bolt timing chain, a new engle cam and had the new set of valves seated. Not something I want to go through again. Loctite is your friend.

[ViperMan]

3-bolt - yeup, got it. 

Thanks for all the rocker info.  Can someone please tackle my question about maximum lift, etc?

I can't remember what centerline means, but I remember reading up on it before.  I'll do more homework to figure that out.

Thanks, guys.

Jeff

[Chryco Psycho]

the length of the rocker is canged to alter ratio , so if the pushrod sits closer to the rocker shaft the ratio is increased
the rockers will have a screw in them with a locknut to adjust lash , all alum heads I know of use rocker shafts , it is the strongest & most stable design
 Max lift is more to do with head flow , for example a stock Iron head will not flow more air even wioth more lift around .500 lift , but my iron heads ported are still increasing air flow @ over .650 lift
 most cam designs are limited to around .620 lift with streetable duration

[ViperMan]

I'm guessing that duration is longer for race applications than street applications, correct?  So what is a recommended "aggressive" street duration at say .580" lift?

Jeff

[Chryco Psycho]

depends what RPM you want the power at , generally I end up in the 240* - 250* @ .050 lift range for street with Mechanical cams

[ViperMan]

Alright here's another question (it's a good thing I'm hijacking my own thread!)

I'm still thinking hydraulic roller.  I want the longer life, and the lower maintenance, but the extra power from less friction.

I'm looking at Comp Cam that advertises different durations for intake and exhaust, AND different rocker ratios for intake and exhaust.

Why?

[Chryco Psycho]

generally the exhaust is poorer flowing so the exhaust has a bigger profile to compensate