Cam question...need your help!
07-05-2011, 09:08 AM
#21
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well... the standard advice is that reducing advance will push the powerband toward higher rpms. The standard advice is also that when designing a cam to optimize a given system and create desirable attributes, the focus needs to be on valve events. Messing with the advance shifts all valve events.
I think most folks will plot out the valve events with special attention to EVO, IVC, duration, split, etc. - then, when creating the camshaft specification, advance will need to be applied because the intake lobe centerline and the exhaust lobe centerline will not happen to be equidistant from TDC.
One last comment on advance... More advance opens the exhaust valve earlier and this tends to help an exhaust-restricted motor make power. However, more advance will also close the intake valve earlier. This tends to bring the peak torque lower in the rpm range. So, especially in your case (stock exhaust), I think the focus should be on valve events - not advance.
I'm using LS6 valves and shimmed PAC 1518 springs. I'd recommend taking a look at the Lunati duals. Folks seem to like those and they're reasonably priced. Link
I think most folks will plot out the valve events with special attention to EVO, IVC, duration, split, etc. - then, when creating the camshaft specification, advance will need to be applied because the intake lobe centerline and the exhaust lobe centerline will not happen to be equidistant from TDC.
One last comment on advance... More advance opens the exhaust valve earlier and this tends to help an exhaust-restricted motor make power. However, more advance will also close the intake valve earlier. This tends to bring the peak torque lower in the rpm range. So, especially in your case (stock exhaust), I think the focus should be on valve events - not advance.
I'm using LS6 valves and shimmed PAC 1518 springs. I'd recommend taking a look at the Lunati duals. Folks seem to like those and they're reasonably priced. Link
02-06-2012, 03:45 AM
#22
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Update Just a little update of this thread.
After all the good info in this thread i did some further research about valve events. Downloaded a "DCR calculator" to calculate valve events. And ordered a custom cam 216/226 (@0.050 lift) 116 LSA on comp cams good old XE Lobe.
It's a mild lobe and it's easy on the valvtrain but should be much more powerful than a LS6 cam, stealthy and emmision friendly.
Right what i looked for.
I'll install the cam as soons as temperature rises, now it's -15°C out there.
After all the good info in this thread i did some further research about valve events. Downloaded a "DCR calculator" to calculate valve events. And ordered a custom cam 216/226 (@0.050 lift) 116 LSA on comp cams good old XE Lobe.
It's a mild lobe and it's easy on the valvtrain but should be much more powerful than a LS6 cam, stealthy and emmision friendly.
Right what i looked for.
I'll install the cam as soons as temperature rises, now it's -15°C out there.
