I would like to learn more also, I don't know much about camshafts. I'm finding it difficult to choose cams for my rotrex K24 build.valves staying open longer would mean more potential for more energy but you are asking about duration as it is not related to lift and valve motion.
So for a given lift and head flow characteristics like an OEM honda head, under the valve motion model to keep jerk as low as possible and everything working great, duration is what it has to be.
We also do not split duration and intake and exhaust together is what makes the whole thing work.
Porsche Gt3, porsche cup engines, M3 racing engines etc etc use close to 290 duration and we only go that high on lifts beyond 600 if the valve motion can handle it.
One of the reasons behind this is harmonics but from a frequency point of view.
The truth is that you can put anything on these lobes and the engine might run and might even make some power but doing it the right way and saving tensioners on the way and not breaking chains or cam cores or engines or heads, or rollers, means that you have to follow all rules and design with honda oem valve motion is mind which is based on the geometry and nothing else.. The cams do not know what head you are using, or fuel or compression, only they tell the valves is how to open and close and the rest is HP somehow.
Let's assume at 6000 RPM, you are using a spring with 27000 cycle per minute natural frequency its around the 9th harmonic.. as RPM goes up, harmonic order goes down. At 9000 RPM, if you do not have control of these things, specs do not matter.
That is why there is a great aftermarket tensioner market because noone in their right mind will take the time to expain why to an audience full of doubters, haters and for the most part not serious about performance.
Email me at svmcams.com if you want to talk about this more, not because I want to sell you a set of cams, but to help you understand when I have time to reply.
As long as RPM is kept under 7000 rpm on normal cars, bad design habits will not show themselves as much... the higher the RPM the greater the need for precise opening and closing of the valve with velocities and accelerations all working the same way on each cylinder and minimum deflection at high rpm, all these things make a difference, a huge difference.
My gut says the motor with the ported head will make more power and the curves will separate around 4000 rpm. I bet the motor with the stock TSX head won't make power past 7800 rpm.The cams I am referring too are Drag Cartel 3.2 cams. Not huge cams. Rev limit is 8500rpm.
I did, just 11.1cr though just in case I wanted to boost it.My gut says the motor with the ported head will make more power and the curves will separate around 4000 rpm. I bet the motor with the stock TSX head won't make power past 7800 rpm.
I thought you decided to go with a built short block...?
Yeah I remember that post, but I would blame the cams not the head for that result.I did, just 11.1cr though just in case I wanted to boost it.
I saw a stock TSX block with a 4p 156 head and drag cartel 2.2 cams stop making power before 8k I believe. IIRC it was in the posted in the stock block thread a few months back.
I think too much for my own good sometimes lol
I'm using Manley H-beam rods in my motor, picking a rod was the biggest headache of the entire build for me. From everything I've researched, these rods are pretty good. When I checked 4piston's website, they seem to use these for their builds on their short blocks so that helped a lot in choosing them.Yeah I remember that post, but I would blame the cams not the head for that result.
FWIW, I'm thinking of doing the same thing with my 2.4...quality aftermarket rods and ~11.1 cr just so I don't have a broken OEM piston or rod explode on a mis-shift and bend all the expensive valves in my cnc head.
With a stock block, you will need a professionally ported head, upgraded fuel system with proper fuel, and stage 3 cams to reach ~280 hp NA. You will also need a ported RRC or a carefully chosen aftermarket intake manifold. Even then, your goal HP is unlikely on a stock short block.What I have :
K20Z1 head STOCK port with supertech nitrated valves, springs H1021D (92) + retainers
I need cams for N/A street application , looking to hit 280-300 WHP with supporting mods.
What cams would you recommend.
I know of one person with a freshly built K24a2 with 2011 TSX pistons, upgraded fuel system, k20a2 head, and prayoonto stage 3 cams who made 268-272.Were stock heads even up to 270? Man that seems high, but I haven't followed NA builds that much, let alone within the past 2 years.