(4th preface) 9/1/08
stock intake has 195 duration and .354" lift
euro cam has 207 duration and .378" lift
exhaust cam has 215 duration and .402" lift
the exhaust cam phased correctly should yeild a bigger intake charge than the euro cam, if the intake system and exhaust flows enough to not cause a restriction.
this will make a cams set pretty close to the TT street set without spending $380
read this and look at the pics, these are pics @ 112*lsa not 110* lsa
this quote of myself (I like quoting myself ) pretty much sums up everything
because I'm lazy and need to go out and swap my ignition distributor, I'm pasting this pm re-hash for all
weeblebiker (2:17 AM 6-7-2007): hehe
k, first, what's your red line?
second, have you looked at the pics and understand how I'm orienting and referencing the cams?
remeber looking at the pics, the cams are spinning counterclockwise advance is counterclockwise, retard is clockwise
rotating the gear 3.6*counter clockwise (which is rotating the cam clockwise or retarding) puts the cam in phase with the intake cam. the stock cam set has a lobe separation of 107* I origenally was shooting for a lobe separation of 112* 3.6* +(112-107)= 8.6* counterclockwise
or 14.4* (tooth seperation angle) - 8.6*= 5.8* clockwise and found this pulled up to my redline 7500 rev limit.
on further research, I found most cam sets of this duration put the lobe separation @ 110*
rotating the cam gear 3.6*+3*= 6.6* counterclockwise. the diameter is 34mm at the gear; 0.2967mm=1* which is shaving 2mm or 1/2 off the key. this should be pretty damn near best for street and stock rev limit, (but will increase overlap and may effect emissions). for you, cutting a new keyway, all you need to do is take this angle offset and add multiples of 14.4* to put the keyway where you want.
and yes decking it will slightly retard the timing, might but not much. to be noticable
weeblebiker (2:20 AM 6-7-2007): as for the new timing mark, set the cam on the counter with the lobes closest to the gear straight up, count 3 teeth up the bottom left and mark the tooth, just like the intake cam your looking at next to it, remeber the intake cam is the reference. when your done the lobe center on the new cam should be slightly clockwise of the intake lobe center
5/31/07 here's pics
don't read this. check 7 replies down for the simple version
Well ok read this for a brief history of the thoughts on this mod
check the links also,
please exuse some of the posts, I was usually writing these in the middle of the night when I was up with my then few week old son
(origenal first post beginning)
Bear with me here,
I'm thinking the old 6* or 7.2* retarded legend was in crank degrees, not cam degrees which corisponds quit nicely to the 3.6* cam degree advance to put the exhaust cam mod in phase with the stock intake.
as discussed in the thread
the exhaust cam has a larger duration 215* verses 195 for the stock cam(I know what that really means now ). 180* is the piston moving from tdc to btc or half a stroke. the mod cam in the stock phase position would make the intake valves open a little sooner in the exhaust stroke which isn't really good. but retard the cam and too much and it leaves the valves open longer during the compression stroke which isn't really good either.
I learned a lot from this graph this morning
according to the TT site
the stock phase angle is 107*
for a refresher of the only seemingly legit info on this mod checky here
which says to put the mod cam at 106* phase angle, which is crank 1* retarded verses stock, or .5 cam degrees
the exhaust cam mod advanced 3.6 cam degrees or 7.2 crank degrees would have a phase angle of 107and be in the same position as the stock cam. (this looks right by my eyeball)
to decrease the valve overlap to a reasonable amount and not have the intake valve open too long during compression stroke,phase angle of 106* has been suggested. you would move the cam 6 crank degrees, (sound familier?) or 3.1 cam degrees
since the cam gear has 14.4 degrees per tooth, somebody thought 6 crank degrees was cam degrees and was about half a tooth and lead back to 7.2* only as cam degrees (again a familier number from up above?) leading to the "half a tooth off thing everybody states", although entirely wrong.
so I think,
to get the cam mod entirely right,
I will advance the cam 3.1 cam degrees (as close as I can) by rotating the cam gear 3.1* counter clockwise. this also make 106* phase angle.
to "Install them with a 106 degree peak opening point on both symetrically", I'll advance both cams .5 crank degrees or .25 cam degrees with the timing gear. which makes sense cause you want the overlap centerd over TDC.
does decking the head advance or retard timing?
Modified by weeblebiker at 6:08 PM 3-19-2006
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Modified by weeblebiker at 6:59 PM 9-16-2008
Modified by weeblebiker at 3:43 PM 1-17-2009
Modified by weeblebiker at 4:15 PM 1-17-2009