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Big cam 1:1 rockers OR small cam ratio rockers

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Hooty481

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Big cam 1:1 rockers or lower lift cam ratio rockers. Just saying you get the same lift which would perform. Advantages/ disadvantages... Cuss/discuss...
 
big cam needs block clearance. Lifts around .290 and above start hitting around lifter area and can hit around the rod journal. Good shaft mounted ratio rockers are expensive where the champion shaft rockers which are 1to1 are only 30 bucks. Pick your poison.
 
Hooty481 said:
Big cam 1:1 rockers or lower lift cam ratio rockers. Just saying you get the same lift which would perform. Advantages/ disadvantages... Cuss/discuss...
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Think of this tho.. the valve will see the same lift (very close) as the lobe with stock rocker ratio.. so at like .200 lift the valve sees .200... but with a 1.3 ratio rocker it sees .260.... A ratio rocker doesn't just make the total lift more..it makes it more throughout the entire lift range.
 
You also get some adjustability too cause you can spilt rockers in many ways to change things a lil to fit what ur for
 
youngengines said:
Think of this tho.. the valve will see the same lift (very close) as the lobe with stock rocker ratio.. so at like .200 lift the valve sees .200... but with a 1.3 ratio rocker it sees .260.... A ratio rocker doesn't just make the total lift more..it makes it more throughout the entire lift range.
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:) Preach it Barry. It snaps them open at a different rate. The ratio rockers will make more hp
 
Here's an example.. you set up using 1-1 rockers but the power ur looking for isn't there you can try a 1-3 set for a lil more... i have split rockers many times too... say you make good power but you think your header may be too small for your set up you can put a 1-1 on the intake and use a 1-3 on the exhaust to test what a lil more exhaust flow would do for you...idk your set up but use plain old stamped rocker (high 6k to mid 7k) any thing over 7500 in my opinion look at a set of shaft rockers... the stamped ones start doing funny things and just don't like that many rpm
 
Tell me where I'm wrong, if you could get the higher lift cam in the engine, you could grind the profile to get the exact same acceleration and deceleration rates as the 1-3 rockers.
 
Just a thought from building automotive engines with flat tappet lifters, if the ramp angle on the cam is too steep the lifter can bind into the cam and wear out the lobe. I'm not sure if that could be an issue with the bigger cam and 1:1 rockers trying to mimic the valve lift rates of the smaller cam and 1:3 lifters...
 
so is there a lot to gain with ratio rockers, on H.P.
youngengines said:
Think of this tho.. the valve will see the same lift (very close) as the lobe with stock rocker ratio.. so at like .200 lift the valve sees .200... but with a 1.3 ratio rocker it sees .260.... A ratio rocker doesn't just make the total lift more..it makes it more throughout the entire lift range.
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Ratio rockers not only add more total valve lift, but they speed up the ramp of the cam. With cams like the CM or .308 from Dyno I have seen moderate peak power gains with ratio rockers. The biggest gain I usually see is with the power curve. Ratio rockers will help make the power sooner and keep the power longer. I will say you are better off using ratio rockers on cams with duration below .250 because of the ratio speeding up the ramp may require a stiffer or dual spring. Now if you plan on using ratio rockers on high duration cams like the F275 or cams in that same profile that already have a fast ramp, you will need to greatly increase your seat pressure to stop the valve at full lift. A fast ramp cam and ratio rockers act like a catapult to a valve. It makes power but needs dual springs with 45+ seat psi.
 
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The Dyno CM is .265 lift. 26 lb springs will be ok with 1:2 ratio rockers, but might be in the low side with 1:3 because it will increase the lift to around .345. You should be ok if you don't try and turn the engine over 8000.
 
I run a 308 with 26 springs and 1.3 rockers I also run a 356 with 32 springs and 1.1 rockers
if my math is right a 308 with 1.3 is 400 at the valve and the 356 with 1.1 is 391 at the valve.
so you see its just about the same.
 
modifiedman said:
I run a 308 with 26 springs and 1.3 rockers I also run a 356 with 32 springs and 1.1 rockers
if my math is right a 308 with 1.3 is 400 at the valve and the 356 with 1.1 is 391 at the valve.
so you see its just about the same.
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But the ramp speed will be much faster with the .308 using the ratio rockers and should need more spring PSI and have a longer power curve.
 
modifiedman said:
I run a 308 with 26 springs and 1.3 rockers I also run a 356 with 32 springs and 1.1 rockers
if my math is right a 308 with 1.3 is 400 at the valve and the 356 with 1.1 is 391 at the valve.
so you see its just about the same.
Click to expand...
Which one pulls harder? Or which do u prefer
 
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