Benefits of higher ratio rockers?
Benefits of higher ratio rockers? What are the benefits and drawbacks to higher ratio rockers? Gen 1s had 1.5s. Racers are now using 2.0s. Where does it end? Why did GM go from 1.8s on LS7s back to 1.7s on L92s and LS3s?
Last edited by ramairroughneck; Jul 28, 2007 at 10:40 AM.
I have always heard the higher ratio the better, but never understood why. I think the benefits were more seen years ago with flat tappet lifters because they could run cam profiles that went easier on the lifters and could still gain a lot of lift. I could be wrong but that is my impression.
As far as a LS1 I think the main benefit would be seen at lift values above .650 or so
As far as a LS1 I think the main benefit would be seen at lift values above .650 or so
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Originally Posted by KCFormula
I have always heard the higher ratio the better, but never understood why. I think the benefits were more seen years ago with flat tappet lifters because they could run cam profiles that went easier on the lifters and could still gain a lot of lift. I could be wrong but that is my impression.
As far as a LS1 I think the main benefit would be seen at lift values above .650 or so
As far as a LS1 I think the main benefit would be seen at lift values above .650 or so
Using higher ratio rockers you can get the lift the engine wants within the duration the engine wants without killing the lifters with side loads. You may have noticed the trend to lower mass (lighter) valves, springs, retainers which allow more lift at higher rpm, which may make more power.
Of course is the down side is that pushrod and normal (centeline) loads on the lifter are higher with higher ratio rocker arms. I think we'll see more high-end rockers in the 2.0 and up range in the near future. OK, some are above that now.
Perhaps the truck L92 and the LS3 production engines don't need/want the lift offered by the 1.8s. When choosing rockers you consider not only the lift the valve wants, but the loads in the valvetrain.
As RAR and rpm and cam agressiveness increase, sometimes simultaneosly, rocker arm stiffnes and moment of inertia become more critical. So we want a stiffer, lighter, lower inertia system. Sounds difficult to do...but not impossible, nor cheap!
Jon
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From: Texas, Europe, Iraq & Afghanistan
Aren't there also physical size limits? A camshaft with too big of lift might have a lobe bigger than the journal diameters. Then, you couldn't get the camshaft inside the engine. Thus, the mechanical ratio of the rocker arm allows greater mechanical lift with a smaller physical size.
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Originally Posted by Gregory
Aren't there also physical size limits? A camshaft with too big of lift might have a lobe bigger than the journal diameters. Then, you couldn't get the camshaft inside the engine. Thus, the mechanical ratio of the rocker arm allows greater mechanical lift with a smaller physical size.
just chiming in here but I have a stock cubed LS1 with Comp 224/230 .581/.592 114LSA, with 1.85 Comp Rockers, Ported Heads, and Ported FAST 90/90. The car is a friggin dog. Could all of these modifications be a little too much for stock cubes??? I am just trying to figure out why the car has such a lack of power. I have a set of 1.7's chillin out waitin to go on the car do you guys think this will fix some power issues???
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Originally Posted by transaman98
just chiming in here but I have a stock cubed LS1 with Comp 224/230 .581/.592 114LSA, with 1.85 Comp Rockers, Ported Heads, and Ported FAST 90/90. The car is a friggin dog. Could all of these modifications be a little too much for stock cubes??? I am just trying to figure out why the car has such a lack of power. I have a set of 1.7's chillin out waitin to go on the car do you guys think this will fix some power issues???
Which heads and whats the intake port volume. Also whats your compression, which valve springs?...And what ICL is the cam installed at...Those rockers put your lift at .632 and .644 which is way to much if you didn't flycut the pistons...
Last edited by chriswtx; Jul 29, 2007 at 06:59 PM.
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Originally Posted by chriswtx
Which heads and whats the intake port volume. Also whats your compression, which valve springs?...And what ICL is the cam installed at...Those rockers put your lift at .632 and .644 which is way to much if you didn't flycut the pistons...
although the 1.85 rockets will have the valve open wider faster.
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From: Concord NC.
Originally Posted by coolmannso
now with the 90mm top you need a 175 hp nos kit too get it to suck air you got the cam kick it
WEEEEEEEE!
Originally Posted by coolmannso
now with the 90mm top you need a 175 hp nos kit too get it to suck air you got the cam kick it
haha jive. right. they are stock ported heads. I have a Nitrous Express Kit with all the fixins but i havent installed it on the car yet. how healthy of a shot you guys think would be safe on the stock shortblock???
Hey thread ****, start your own. I'm trying to learn something. 
Originally Posted by ramairroughneck
What are the benefits and drawbacks to higher ratio rockers? Gen 1s had 1.5s. Racers are now using 2.0s. Where does it end? Why did GM go from 1.8s on LS7s back to 1.7s on L92s and LS3s?
some reading on using higher ratio rockers.
http://vincihighperformance.com/LS1%...HTML#quicklift
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Originally Posted by mrr23
some reading on using higher ratio rockers.
http://vincihighperformance.com/LS1%...HTML#quicklift
http://vincihighperformance.com/LS1%...HTML#quicklift
http://www.mid-lift.com/intro-mid-lift.htm
It's not a short read, and the author, like the Crane author, thinks his is the better method. Read all of the pages. Good food for thought.
Jon
Originally Posted by Old SStroker
It's not a short read, and the author, like the Crane author, thinks his is the better method. Read all of the pages. Good food for thought.
Jon
Jon
Crane LS1 Gold Race Rockers “Too Powerful!” for Daytona!
crane cams newsletter mar 2006
Crane Gold Race® Rocker Arms Dominate Engine Masters Challenge
crane cams newsletter oct 2005
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Originally Posted by mrr23
everyone with an idea think theirs is better. it's how they can back it up is where it gets interesting.
Crane LS1 Gold Race Rockers “Too Powerful!” for Daytona!
crane cams newsletter mar 2006
Crane Gold Race® Rocker Arms Dominate Engine Masters Challenge
crane cams newsletter oct 2005
Chevy High-Performance Magazine LS1 Project Truck Gains Average 20 HP
Crane LS1 Gold Race Rockers “Too Powerful!” for Daytona!
crane cams newsletter mar 2006
Crane Gold Race® Rocker Arms Dominate Engine Masters Challenge
crane cams newsletter oct 2005
Chevy High-Performance Magazine LS1 Project Truck Gains Average 20 HP
I really don't uderstand why they mandate stock rockers in some classes. Not to say the LS engine rockers are not quite good, but unless the class requires hydraulic lifters, it's tough to use the non-adjustable stockers on a solid. Possible, but not easy with stud mounts.