[enkeivette]

Guy... YOU JUST PROVED MY POINT! Come on man, admit you were wrong. You went on the comp website searching for similar cams and you still couldnt even find one!

What you posted is a 232/234 duration .595/ .6 lift LS1 cam, and a 230/236 duration .570/ .576 lift SBC cam. The LS cam has more lift, for a roughly equivalent duration. Admittedly, a closer gap than what I usually see, but still congruent with what I said. LS cams, less duration, more lift than SBCs.

Find a SBC cam with a .6 lift cam, and the duration will be ridic. Now stop trying to prove me wrong and start discussing why there is a difference.

I'm thinking, with more valve surface area you need less lift to flow the same amount of air? Maybe thats why this 420A 4 valve motor has way less lift.

[enkeivette]

Yup, LS1 valves are smaller. 2.02 vs 1.89

It makes total sense if you think about it. As the valve lifts, it creates a cylindrical port for air to flow through. And the wider the valve, the less it needs to move (shorter the cylindrical port needs to be) to have the same surface area opening.

[enkeivette]

Originally Posted by enkeivette

Learned something, thought I'd share.

Camshaft duration is a measurement of how long the valve stays open in crankshaft degrees. And the measurement is taken from one specific lift point to that same closing point on the closing end of the ramp.



But, since duration is measured at the cam itself from the manufacturer you would think that rocker ratio is totally independent of this. Well yes, and no, and yes again.

What really matters is the lift at the valve (obviously) and if we measure the lift at the valve at a specific point (say .05 again) with a higher ratio rocker, the valve will reach that point slightly sooner and slightly later, creating a slightly longer degree arc.

Although, if we were to measure valve lift at .00000000000000000000001 (you get the point) there would be no difference in duration, as the cam begins to lift the valve when it begins to lift the valve, period. Rocker ratio cannot change this. However, we do not end the measurement at the very closing point of the ramp. Why not? Probably because there is a negligible amount of air flow at .00000000000000000000001 lift.

Is your head spinning? Mine is.

So in conclusion, yes rocker ratio can affect dynamic duration. The rule of thumb seems to be 2 degrees for every .1 ratio on the rocker arm.

In otherwords, if you had 220 degrees of duration with a 1.6 rocker on an LS1, you'd have 222 degrees with a 1.7 rocker. My cam is a 236 in, 242 ex. split duration with a 1.5 rocker and with my new 1.65 rockers, my duration will jump to 239 in. and 245 ex.

Ya, I understand the fuck out of cams bitches. Coming soon: Apollo Cams. Wheres 5.0 blow to make fun of my ego again?

[Shaolin Crane]

Originally Posted by enkeivette

Guy... YOU JUST PROVED MY POINT! Come on man, admit you were wrong. You went on the comp website searching for similar cams and you still couldnt even find one!

What you posted is a 232/234 duration .595/ .6 lift LS1 cam, and a 230/236 duration .570/ .576 lift SBC cam. The LS cam has more lift, for a roughly equivalent duration. Admittedly, a closer gap than what I usually see, but still congruent with what I said. LS cams, less duration, more lift than SBCs.

Find a SBC cam with a .6 lift cam, and the duration will be ridic. Now stop trying to prove me wrong and start discussing why there is a difference.

I'm thinking, with more valve surface area you need less lift to flow the same amount of air? Maybe thats why this 420A 4 valve motor has way less lift.

OMG are you kidding me? Look at the base circle, not the advertised lift. a cam can be whatever the fuck lift you want it to be a factory SBC rocker ratio is 1.5 vs 1.7 for factory ls1

Here is your SBC Cam at a 1.7 Ratio Vs the ADVERTISED 1.6
Lobe Lift 0.361
VALVE LIFT .614/.607
Duration at .050 231/237

It's the same fucking cam, same profile grind, same shit different motor. ENGINE stuff, not brand. The neglegible difference in the specs is because one is a 280 Profile and the LS is a 281 Profile

Come on now, i'm a cave man and even I figured out the math.

[enkeivette]

Advertised lift is all that matters!! Thats how much the valve is moving! Who gives a shit what the base lift is!

[enkeivette]

They design the cams with that fact that LS engines have different ratio rockers in mind. Duh

[fiveohwblow]

Originally Posted by enkeivette

Ya, I understand the fuck out of cams bitches. Coming soon: Apollo Cams. Wheres 5.0 blow to make fun of my ego again?

What's your obsession with me Adam? You're still offended because I don't like gm and that has what to do with this thread? I never spoke up in here until now, nor did I attack you or mention your ego. You're on some serious shit man.

[Shaolin Crane]

Originally Posted by enkeivette

Advertised lift is all that matters!! Thats how much the valve is moving! Who gives a shit what the base lift is!

Lobe lift is lobe lift is lobe lift. Not only did I prove you wrong, but I proved the SBC can is LARGER than the LS can. A rocker has absofuckinglutily nothing to do with the physical metal of the can. Rocker is simply something that aids in customizing your needs. Isky designed these profiles decades ago and EVERY OHV V8 uses them.

What don't you get, you don't pic a cam based off what was factory, you go by the parts needed and the physical lobe lift every time. I have 1.72 Rockers in the blower motor and I have 1.6 Rockers in the race motor. Does that make any difference to what the actual cam specs are? Nope.

[94cobra69ss396]

There's a lot of arguing over nothing really. Adam, your buddy can adjust the LSA to whatever he wants. So have him put it on a dyno and run it with a 114 LSA and a 110 LSA and see what difference it makes.

[Shaolin Crane]

Originally Posted by 94cobra69ss396

There's a lot of arguing over nothing really. Adam, your buddy can adjust the LSA to whatever he wants. So have him put it on a dyno and run it with a 114 LSA and a 110 LSA and see what difference it makes.

Seriously, i dont know why this has lasted so long.