ChrisH Posted September 30, 2009 Report Share Posted September 30, 2009 I'm thinking about replacing the cams in my motor with something more exciting. I've been looking at some aftermarket replacements and i'm a little confused about the specs of them. I'm aware that this is a complex subject, as valve lift and timing of full lift will also affect the operation of the different cams, but i'm trying to clarify the basics. The standard cams have these values: Duration Inlet 316 Deg Exhaust 292 Deg and timing of In 55/81 Ex 47/65 A couple of values for the aftermarket cams are: Duration Inlet 250 Deg Exhaust 248 Deg and timing of In 20/50 Ex 49/19 or Duration In 245 Deg Ex 242 Deg and timing of In 21/45 Ex 45/17 So, what kinds of difference would the two lower set of cams have? From what i can see they seem to have a smaller duration that the stock cam, which i was thinking was odd. Also what affect do the timing have? Would i be right in thinking that the duration is the amount of time the valve spends open? Cheers (and blame Levo for this, making lurkers post...it's all his fault you know....!) Link to comment Share on other sites More sharing options...
Stealth Posted October 1, 2009 Report Share Posted October 1, 2009 I'm thinking about replacing the cams in my motor with something more exciting. I've been looking at some aftermarket replacements and i'm a little confused about the specs of them. I'm aware that this is a complex subject, as valve lift and timing of full lift will also affect the operation of the different cams, but i'm trying to clarify the basics. The standard cams have these values: Duration Inlet 316 Deg Exhaust 292 Deg and timing of In 55/81 Ex 47/65 A couple of values for the aftermarket cams are: Duration Inlet 250 Deg Exhaust 248 Deg and timing of In 20/50 Ex 49/19 or Duration In 245 Deg Ex 242 Deg and timing of In 21/45 Ex 45/17 So, what kinds of difference would the two lower set of cams have? From what i can see they seem to have a smaller duration that the stock cam, which i was thinking was odd. Also what affect do the timing have? Would i be right in thinking that the duration is the amount of time the valve spends open? Cheers (and blame Levo for this, making lurkers post...it's all his fault you know....!) This might help explain it... http://www.pipercams.co.uk/NewPiperWeb/red...TechAdvice.html Link to comment Share on other sites More sharing options...
ChrisH Posted October 2, 2009 Author Report Share Posted October 2, 2009 Thanks for that. Going from the figures provided then, the stock kwack cams are much hotter than the aftermarket replacements!! The only thing i can think of is that the Kwack cams don't provide as much lift as the 'hot' cams (but i can't find any numbers to back this up with) Link to comment Share on other sites More sharing options...
Mark/Foggy Posted October 2, 2009 Report Share Posted October 2, 2009 Think you'll find that the 'kit' cams are a lot more agressive. The ramp at the valve, snaps them open much quicker and gets off so that the springs can slam them shut quicker. Leads to more stress & wear, but well, you know that tuning has it's costs. Link to comment Share on other sites More sharing options...
Evilchicken0 Posted October 3, 2009 Report Share Posted October 3, 2009 You might need stiffer valve springs and it's best use slotted cam wheels to allow the tuning to be bang on. You might get some improvement just by fitting the slotted cam wheels and lining the cams up. Link to comment Share on other sites More sharing options...
Instant Gymnast Posted November 12, 2009 Report Share Posted November 12, 2009 Hi AV, it depends on the budget for the job. If money isn't a factor then kit items are the daddies, but have you thought about getting yours re profiled? They won't be as wild as race cams, more of a fast road spec. The bonus being you keep the bottom end torque and you gain a storming top end. Also because the lift and duration are mid way(roughly)between race and road, you don't have to go to the expence of new springs, retainers and possibly valves. Remember the kit cams were for racing and will have all the power at the top end and you may not get the gains you hoped for without time spent porting and polishing. Adjustable cam sprockets are another option to get the timing spot on. I could not afford them when I had my ZX7-R engine built so my engine builder pressed them on and off a couple of times and got them as near as damn it. I was really pleased and am not of suficient tallent to notice the odd horsepower I might have missed out on. Once it was above 3500 it pulled like teenage boy and with the lower gearing I had useable, available power all the way to the red line! If you want a chat with the engine builder, it was Dave Wood at DWR in Aylesbury on 01296 336750. Tell him Colin sent you. Link to comment Share on other sites More sharing options...
ChrisH Posted November 14, 2009 Author Report Share Posted November 14, 2009 Cheers Instant (col)! I was looking at Piper and Kent as they both can re-profile stock cams as well as provide something a bit more aggressive. At the moment things are on hold with the bike anyway, and unless i can find a decent full system at sensible money then i think the cams will have to wait until next winter. For sure though, it's something to consider. Link to comment Share on other sites More sharing options...
Evilchicken0 Posted November 21, 2009 Report Share Posted November 21, 2009 You'll probably find fitting raceier cams will give "more" than a system, depending on the year and the emission regs. Why not ask the cam company what you can expect ??? Link to comment Share on other sites More sharing options...
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