J
jpward
Guest
Adjustable Cam gears on standard head benifits?
Yes or no?
Yes or no?
boucherie
New Member
ive got a set of adjustable pulleys that i was going to wait and fit on the spare engine, but if theres genuine gains to be made on the standard cams then how much do the adjustments need to be on the pulleys?
has anyone actually done this and if so what problems did they encounter?
has anyone actually done this and if so what problems did they encounter?
J
jpward
Guest
From what i have found out Paul;
It is better to retard the cam than ignition to reduce Det
More cam over lap as in more time when exhaust is closing and inlet vales open promotes scavenging but loses mid-range, too much will see over-scavenging and a loss of some of the mixture
Less over lap improves mid-range, too much will see bottom end disapear
The graph above expresses the change of engine characteristic when shifting intake valve timing by sliding adjust pulley. If intake valve timing is advanced (ex; 120‹to 110‹), engine output at low RPM will be gained. On the other hand, if intake valve timing is delayed (ex; 110‹to 120‹), engine output at high RPM will be gained.
So really it would seam a good idea to have them as your optimum points of open and close, change with different mods like 3" exhaust and inlet time spent on dialing them in on the other hand could be vary between those wanting to screw every last hp out or just a little by those wanting a better timed engine like me with a standard flow head.
It is better to retard the cam than ignition to reduce Det
More cam over lap as in more time when exhaust is closing and inlet vales open promotes scavenging but loses mid-range, too much will see over-scavenging and a loss of some of the mixture
Less over lap improves mid-range, too much will see bottom end disapear
The graph above expresses the change of engine characteristic when shifting intake valve timing by sliding adjust pulley. If intake valve timing is advanced (ex; 120‹to 110‹), engine output at low RPM will be gained. On the other hand, if intake valve timing is delayed (ex; 110‹to 120‹), engine output at high RPM will be gained.
So really it would seam a good idea to have them as your optimum points of open and close, change with different mods like 3" exhaust and inlet time spent on dialing them in on the other hand could be vary between those wanting to screw every last hp out or just a little by those wanting a better timed engine like me with a standard flow head.
P
pulsarboby
Guest
it depends on what cams you are installing, as to what adjustments need to be made ian;-) cams have different duration and degree as you well know, which will govern the setting to be made.boucherie said:
also it depends on whether you have had headwork done or a skim to the block face, all these factors have to be taken into the equasion.
a lot of people buy them as they look good, even though you cant see them:der: and others will buy them because they think there weight saving:der:
and others buy them because they have either had the block or head skimmed, which is good as you can bring the un-tensioned side of the chain taught, which will allow you to set timing back to zero degrees tdc
but im not voting as its a silly question really:lol:
Good reading bud.jpward said:From what i have found out Paul;
It is better to retard the cam than ignition to reduce Det
More cam over lap as in more time when exhaust is closing and inlet vales open promotes scavenging but loses mid-range, too much will see over-scavenging and a loss of some of the mixture
Less over lap improves mid-range, too much will see bottom end disapear
The graph above expresses the change of engine characteristic when shifting intake valve timing by sliding adjust pulley. If intake valve timing is advanced (ex; 120‹to 110‹), engine output at low RPM will be gained. On the other hand, if intake valve timing is delayed (ex; 110‹to 120‹), engine output at high RPM will be gained.
So really it would seam a good idea to have them as your optimum points of open and close, change with different mods like 3" exhaust and inlet time spent on dialing them in on the other hand could be vary between those wanting to screw every last hp out or just a little by those wanting a better timed engine like me with a standard flow head.
Like you, i'd go for them on the standard(ish) set up, to get the very most out of it.
gtirx2
Member
Bit off topic here but i have been reading about when you skim your head you should fit adjustable cam gears as the timing will be slightly out.Well my head has been skimmed to its limit and when it went on the rolling road it had a bit of a dip between 5000-5500rpm and i was wondering if this maybe the cause?
But my main question here is how would skimming the head affect the cam timing on standard cams/gears,would it be advancing the exhaust and inlet cams to open earlyer or retarding them?Also how many degrees would it put the cams out by skimming the max 0.2mm off the head?has anyone fitted adjustable cam gears on standard cams because they have skimmed the head and if so how far out where they?
But my main question here is how would skimming the head affect the cam timing on standard cams/gears,would it be advancing the exhaust and inlet cams to open earlyer or retarding them?Also how many degrees would it put the cams out by skimming the max 0.2mm off the head?has anyone fitted adjustable cam gears on standard cams because they have skimmed the head and if so how far out where they?