LSx007

iTrader: (3)

i have a 347 froged ls1 ,, tsp 5.3l and ms4 ..
looking at a set of harland sharp rocker arms gonna also run comp lifters..

now the ? is do i stick with the stock ratio 1.7 or the 1.8 ..
any differnece .. rpm power torque ? i already got the tSP harden push rods..

if i decide to go with the 1.8 ratio rockers will the pushrods differet lenght ?

anyone who can help please do im in the process of ordering them any day now .
thanks

chopper

iTrader: (18)

There is plenty to take into consideration with this...
1.8 versus 1.7 ratio rockers will change lift at the valve and duration @ .050.
More importantly it also reduces piston to valve clearance.
I don't know the specs of Your cam so lets use a number of .600 lift at the valve for reference using 1.7 ratio rockers. Take .600 divide by 1.7=.3529411.
This is the lobe lift at the cam. Then take 1.8x.3529411=.6352939. This will be the lift at the valve with 1.8 ratio rockers, rounded off it is a gain of .035 at the valve and reduces piston to valve clearance the same amount.
The reason it affects duration is due to the higher ratio rocker it will achieve .050 lift at the valve sooner on the same cam.
Is this good? Your tuner might be able to answer this, more lift and duration helps some engines and hurts others. People like Patrick G. can answer very few others can.
It is also a better practice to check push rod length with a checker and then order the correct length rather than order some and hope they will work. You might want to do some more reading before ordering any more parts. Try the stickies and ls1howto.com.
Bottom line, You must know piston to valve clearance and check for correct length pushrods. Carl.
Hope this helps

teke184

iTrader: (5)

most bigger cams these days havee too fast of a ramp rate to allow the use of higher ratio rockers.

and the MS4 would be one of those cams i am willing to bet.

so your only option is 1.7s

Old SStroker

Ask your engine designer or at least your valvetrain designer. If this engine is completely DIY, be careful with some of the information being presented above. It doesn't seem to come from folks who have sucessfully done LS eingnes/valvetrains.

Dragkid1917

iTrader: (2)

no way dnt do it with an MS4..... The most i would ever do is get the 1.75 from crane.. but even then.... idk

RE AND CHERYL

iTrader: (31)

Most cams for the LSx motors aren't recomended for rocker ratios greater than stock for street driven motors. Even a mild cam like the MTI Stealth II cam I'm running is not recomended for use with 1.8 ratio or greater RRs. They would work just fine, the problem is they would trash your valve springs due to acceleratedramp rates.

Re'

vettenuts

iTrader: (4)

There can be advantages to higher rocker ratios, but there is some luggage that comes with it. You need to make sure your valve train geometry is right on the money, you need valve springs that are up to the task. You will also be putting more load into your lifters, are they able to handle the larger loads. You also need to examine your seat and over the nose valve spring forces and you need to make sure the rocker arm is stiff enough to handle the loads and accelerations that come with this. My personal impression of the Harland Sharp rocker arm just from looking at them is they are not as stiff as the Crane or Yella Terra rocker design. If you plan on going with Harlands, I would stick with the 1.7's but you still need to verify your wipe pattern during installation, don't just bolt them in place and call it good. Once you have the wipe pattern verified, then check the pushrod length requirements. Pushrods should be the last part you order, and should be measured with the head in place with the rockers properly set up.

eallanboggs

iTrader: (1)

You can accomplish the same result of using a higher ratio rocker by going with a cam with more lift and duration that is ground for a 1.7 ratio in the first place. By using a rocker that is different than the one the cam is intended for will either increase or decrease the lift and duration depending on whether the ratio is higher of lower than intended. That being said I believe many retailer recommend against using higher ration rockers at a certain lift and duration point to avoid reliability issues, but they never seem to explain how they arrive at this threshold point. If your too close to P/V problems by adding an additional 0.035" of lift then you need to stay away from a higher ratio. Otherwise don't dismiss them out of hand if your other components are of equal quality(better springs, pushrods, lifter, etc.). There are a lot of quality higher ratio rockers available so do your homework. You can get Scorpions at 1.8 for $379. It's an easy installation with no rocker cover issues.

LSx007

iTrader: (3)

hmmmm ... i got more than enough pvc ..but if its not recomended with the ms4 then maybe i should just stick with the 1.7 ratios ...

the springs are .650 lift

anyone have any other toughts on the subject ?? power differences ?? before and after install?

chopper

iTrader: (18)

If there is misleading info. in My first post please correct Me, there will be no offense taken. I would like to know what is incorrect. Thanks, Carl.