ò Belief 1. I believe that cam timing wasn't chosen at random on vehicles, but for an overall balance of many factors, including power and reliability
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True, but di you know that you can slightlyincrease hig end power(at a loss to low end), by advancing you cam timing a a couple degrees, adn slightly increase low end, at a loss to high end by retarding....
You may *want* a free lunch, but it's very rare to find a working perpetual motion machine. If anyone wants to call a major automotive systems engineer or even a cam design shop and get facts, I'd be willing to listen.
Okay, how about someone who has worked ina speed shop, that has worked with Callaway, adn Lunati... regardless.
Anyone I have built enough motors, adn still do regularly, to know what I am saying.. you may not want to believe, or agree with me, "because I seem to young to know anything"..
But Wayne, we are all familiar with your skeptism, adn thats cool. I can totally go with that. I am the same way with "cheap speed"..and agree there is no such thing..but this isnt what we are discussing here.
GM offered performance cam shafts as RPO options during the 60-70s.. one of 2 ot them were
Off road Specail" cams(one for SBC 327/350), the other for BBC..
Both were solid lifter(adjusting valve lash very frequently), adn both were covered under the factory warranty, as long as they were installed by a GM certified tech...
That is just one example....
ANd honda has come up with a cam set-up..its called VTEC, it has 3 cam profiles.. very effecient, --all the way to very powerfull...(same motor that got 120 hp per liter in the orignal S2000)
Regardless, designers/engineers, have to meet a certain VE(volumetric effeciency), and them make the engine runn smooth at idle, under the load of accersories, maintian a certain vacuum at various points int he rpm band, AND meet EPA/emission standards... and the fact the these motors will be used behind auto adn manaul trans..(which can make a world of difference)
When cams are replaced with aftermarket, there are some comprimises(sp?).. like vacuum, ilde, and emissions..
Second to a super/turbo charger, adn Nitrous, cams produce the most bang per buck of mods, adn if selected properly.. without much, if any difference in reliablilty.
Allt he cam does, is open and close valves.. allowing air in and out. The only time there is a bad side to this, is when you force it in(super/turbo). The motor can only take in so much air/fuel per stroke, and then you get to a point, when the cam isnt worth the money, because you aer losing vacuum at no gain...
Valve lift is the point where you could break stuff, if the cam mfg'r doesnt do their homework, as you can bend.break stems, seals, followers, keepers..etc....
Duration, is what determines the actual power band..lower duration number, the lower the power band, adn usually broader.. just the opposie fro a higher duration number, though there are variations there as well... lobe seperation, and centerline have an effect as well...
There is a lot of science that goes into this, even in a regrind.. then motors are tested, thuroughly, and when a profile works, the keep those numbers, adn run the cam...
Again, I understand your standing... adnI will not say there is no trade-off..there is, your vacuum is lower(though you shouldnt notice that ), you are burning more fuel, adn you are smiling...
As far as longevity,in such a smal cam, no...if you beat the snot out of it..to show the difference in your cam..then yes.
If you do other things to enhance the cam profile, like zero decking the block, machining the head, etc.. then all bets are off.
Teh most common problem with cam profiles, in fuel injection, is with speed density..but thats a whole other ball game....
Chase
