The term "Stage 5" tells you nothing about the cam's profile. The numbers Terry and others have identified as the measures of Ryan's cam profile are really what describes the cam's characteristics
Learn about profile, opening and closing angles, duration, overlap and valve lift. These are all meaningful terms that allow you to compare two or more camshaft profiles and determine which engine characteristics you will get. Generally speaking, the larger the opening duration, the longer the overlap (the cam rotation angle over which both inlet and exhaust valves are open) and the greater the valve lift, then the more fuel you can get in and out of an engine, and the higher power you can get from a naturally aspirated engine, but you need higher revs to get the power, as you recognise. At low revs all these "bigger" actions of valves work against good engine performance characteristics (smooth idle, low speed torque). Hence "lumpy" idle and no power to speak of. EFI helps a bit here. The discussion about Variable Valve Lift (VVL) and Variable Valve Timing (VVT) is the "new tech" way to get an engine to perform like a kitten at low revs, yet have the power of a "lumpy" cam at high revs. These technologies just alter valve lift and valve opening duration (timing) by mechanically altering the camshaft profile as revs rise. ----- Original Message ----- From: "Ryan Ottens" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, 21 March 2002 0:00 AM Subject: Re: cam specs > > thanks all for your help, especially andrew, mark and terry. > im under the impression that this isnt really a cam to suit what im after. > within a week i will have twin 45mm webers, ive already got a ported head > with bigger valves ready to go on too. now just need a lumpy arse cam. > some say stage 5 cam is too much. but chris has one which is prolly > equivilent in his car and says its still streetable. so i guess why not get > something rediculous. not really fussed if theres no power under 3500-4000 > and i know im prolly gonna get some hge fuel bill too. > but would say a stage 4 be more practicle? > > thanks again > > >From: andrew smith <[EMAIL PROTECTED]> > >Reply-To: [EMAIL PROTECTED] > >To: [EMAIL PROTECTED] > >Subject: Re: cam specs > >Date: Wed, 20 Mar 2002 20:36:08 +0800 > > > >Ryan, > >The cam you have is fairly mild as far as lumpy cams are concerned.The > >figures > >he has given you are advertised figures which means they are the opening > >and > >closing points for the valves.The duration at 50 thou opening is 216 deg > >which > >is what some cam grinders give for all there specs.The other durations he > >has > >given are opening and closing durations.Lets start with the inlet which > >opens > >at 26deg btdc and closes at 68deg abdc then add 180 deg which gives 274deg > >duration.To work out the lobe centre line we halve 274 to get 137 which we > >add > >to the inlet opening of 26btdc which we really take off to get 111deg atdc > >centre line(peak lift) for the inlet.We then do the same for the exhaust > >which > >opens at 70deg bbdc and close 26deg atdc then add 180deg to get 276 deg > >duration.To get the centre line we take half of the duration(138) from 26 > >atdc > >to get 112deg btdc centre line for the exhaust.To work out the lobe > >seperation > >we then add together both the centre lines 111 and 112 to get 223 then half > >that to get 111.5 deg lobe sep.All this info comes in handy when dialling > >in > >cams. Grape Ape Drag Racing have a look at this site for some cam info.Go > >to > >the camaro build up then valve train and then scroll down. > >There also some good stuff under technical articles on the site directory. > > > >Ryan Ottens wrote: > > > > > hey list, > > > i just bought a lumpy cam for $30 the other day. > > > now i finally got the specs back of it today. > > > but got no fricken idea on what most of them mean. > > > all i know is the degree of the cam vaguely. > > > this is what ive got > > > > > > timing - > > > open: 7026 > > > close: 2668 > > > > > > duration - > > > Inlet: 274 (the degree of the cam?) > > > Exhaust: 276 > > > > > > at 50thou 216 (wtf?) > > > > > > anyways this is what ive been told. > > > could someone please say 'decifer' this language and tell me what it > >means, > > > and also like how lumpy is it etc etc. > > > > > > thanks again, > > > ryan > > > > > > _________________________________________________________________ > > > Send and receive Hotmail on your mobile device: http://mobile.msn.com > > > > > > > > > > _________________________________________________________________ > Chat with friends online, try MSN Messenger: http://messenger.msn.com > > --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/[email protected]/ ---------------------------------------------------------------------
