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    Thread: High Lift Cams on VTEC springs?

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      High Lift Cams on VTEC springs?

      Hey guys I was just researching high lift cams and I thought is it possible to run them on VTEC valve springs? I think it could work because VTEC has high lift lobes built-in and these springs might be designed for that?

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      High lift cams for which car? There are a lot of other factors you will have to look into before deciding on valve springs. A "mild cam" for street use can be run on stock valve springs provided you keep rpms at sane levels ( stock rpm limit ).

      A wild cam ( lots of overlap and higher lift ) will tend to produce power at higher rpms and you might have to increase your rev limit to make use of the power that the cam can produce. Depending on the engine, you might need more supporting mods as well.

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      Quote Originally Posted by harrie View Post
      High lift cams for which car? There are a lot of other factors you will have to look into before deciding on valve springs. A "mild cam" for street use can be run on stock valve springs provided you keep rpms at sane levels ( stock rpm limit ).

      A wild cam ( lots of overlap and higher lift ) will tend to produce power at higher rpms and you might have to increase your rev limit to make use of the power that the cam can produce. Depending on the engine, you might need more supporting mods as well.
      Any car in general. My question was whether VTEC valve springs from the city may be reliable day in and day out considering that the VTEC cam has high lift lobes built in too.

      For argument's sake, suppose we have a P&P head, well designed custom exhaust and a custom intake system in place, does a high lift cam now seem prudent provided the redline stays the same?

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      Stock springs will do provided the lift of your new cam doesn't cause the valve springs to bind.
      On the esteems though we are limited by the rocker arm design. Cant go for wilder cams because of the rocker arm clearances.

      For a NA build with wild cams, you would ideally need a head that can flow good enough number and still maintain a high port velocity ( often overlooked ), high enough compression to take advantage of the overlaps and extra lift the cam provides for, an intake system that works at the top end of the RPM range ( tuned length or ITBs ), short ratio gearbox which will help keep the engine spinning at the higher end.

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      you still haven't classified the high lift cam comes under the wild category or the mild category. And judging by the way "VTEC just kicked in yo", isn't a high lift cam just supposed to bump up power keeping the curve the same or in other words displace the curve higher up the scale?

      and does it screw up the smooth idle of the stock cam?

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      Quote Originally Posted by MSW View Post
      isn't a high lift cam just supposed to bump up power keeping the curve the same or in other words displace the curve higher up the scale?
      We classify cams as mild / wild / really wild (??) based on the overlaps.
      In layman's terms maybe we could call a cam producing power at 4-5k as mild, 7-8k as wild, 9k+ in the really wild category (??)

      More overlap = more charge dilution at lower RPMs, but better scavenging and hence better VEs at higher RPMs
      More overlap also screws up the idle because of very low vacuum, but you can still get it to idle reasonably well with a stand alone ECU.

      So a wild cam will kind of maintain VEs at higher RPMs, so you rev more and make power ( Power = f(torque * rpm) )

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      Quote Originally Posted by harrie View Post
      In layman's terms maybe we could call a cam producing power at 4-5k as mild, 7-8k as wild, 9k+ in the really wild category (??)
      so that would mean the mild cams are the best bet for mo' powa while still maintaining everyday drivability. But would it need any other parts like rocker arms or stuff, or just the cam is enough?

      PS: POST 100!!!!!

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      Yup, in a very broad sense. Dont think that cams will add power. Its wrong to assume so, though you do get more power.

      Cams will increase your VE in a particular RPM range.

      More VE = More Airflow ( Make sure intake and head can flow that much without restrictions )
      More Airflow = More Fuel can be injected ( Tune the stock ECU or Use a aftermarket ECU )
      More Airflow = More Airflow out of the engine ( Make sure your exhaust supports the cam as well )

      How much power the cam makes for you depends on how well all the above parameters are optimised.

      For most cars you dont have to replace rocker arms, but will have to redo tappet clearances.

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      Ha ha, basically you want the "VTEC to kick in even at lower RPMs yo". So how is it gonna be? Instead of the low lift cam lobe in a VTEC engine for lower RPMs, its gonna be a mild lift, but the VTEC hi lift lobe will still kick in at higher RPMs?
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      Quote Originally Posted by rageshgr View Post
      Ha ha, basically you want the "VTEC to kick in even at lower RPMs yo". So how is it gonna be? Instead of the low lift cam lobe in a VTEC engine for lower RPMs, its gonna be a mild lift, but the VTEC hi lift lobe will still kick in at higher RPMs?
      Not this, but the VTEC high lift lobe for a regular non VTEC cam. So that the "VTEC kicked in at all RPM yo" scenario plays out.

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