XE head question
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Increase the lift rather than the duration if you want to get more air in. That way you retain driveability.
To can pick up a bit more power if you advance the inlet cam a tad this helps with the scavenging which should increase the mid range power a bit, might over scavenge at high rpm's though.
Chris
To can pick up a bit more power if you advance the inlet cam a tad this helps with the scavenging which should increase the mid range power a bit, might over scavenge at high rpm's though.
Chris
increasing the lift on it's own is a surefire way to kill the lifters on the XE - the profile already has a fairly agressive acceleration and the lift already requires piston pockets - many users of wilder cams with standard pistons report excessive tappet noise afterwards.
Also, increasing inlet valve size in the XE should be one of the last things you do - and only on an engine built to take advantage of the extra flow above 6k rpm
concentrate on the head - there's plenty of potential in there - but there's no major restriction in one area that will give a large gain -it's more a case of paying attention to detail and small gains all adding up - the exhaust tract though is especially restrictive - and would show power gains if you had a well matched manifold - don't ever match the exhaust ports to the manifold though if you intend to build a well tuned NA lump - reversion is discouraged by having a good step in diameter.
Also, increasing inlet valve size in the XE should be one of the last things you do - and only on an engine built to take advantage of the extra flow above 6k rpm
concentrate on the head - there's plenty of potential in there - but there's no major restriction in one area that will give a large gain -it's more a case of paying attention to detail and small gains all adding up - the exhaust tract though is especially restrictive - and would show power gains if you had a well matched manifold - don't ever match the exhaust ports to the manifold though if you intend to build a well tuned NA lump - reversion is discouraged by having a good step in diameter.
he wants to know about heads Matt, not anal polyps 
the exh. ports are always generally badly mismatched to the valve seat - all the heads I've seen always have a ridge on the plug side of the port, just below the seat, and another lump on the small radius of the tract.. in general though the ports can be opened out a little too, as the seat is generous and can stand a little opening out.
the exh. ports are always generally badly mismatched to the valve seat - all the heads I've seen always have a ridge on the plug side of the port, just below the seat, and another lump on the small radius of the tract.. in general though the ports can be opened out a little too, as the seat is generous and can stand a little opening out.
420 and 450 in my simple mind are lift figures in thous and not duration. Duration is how long the valve is open for, this is lift, how far down the valve is pressed in thous.
The 420 and 450 that QED do have the same duration as the standard XE cams and just open more, based on what I'm told.
The 420 and 450 that QED do have the same duration as the standard XE cams and just open more, based on what I'm told.
Cams spin at half the rate of the crank.
Duration is expressed in crank degrees. You can get 330 degree cams for drag motors and so on.
I would imagine the 420 and 450 are indeed lift figures.
Cams very intresting things, lobe seperation angles, lift, duration, base circles, ramp, flank, nose and all sorts of other terms.
The port castings usually have a step in them due to the way they are cast, bits of sand that form it fall away and leave a sharp turn at the short turn radius.
Chris
Duration is expressed in crank degrees. You can get 330 degree cams for drag motors and so on.
I would imagine the 420 and 450 are indeed lift figures.
Cams very intresting things, lobe seperation angles, lift, duration, base circles, ramp, flank, nose and all sorts of other terms.
The port castings usually have a step in them due to the way they are cast, bits of sand that form it fall away and leave a sharp turn at the short turn radius.
Chris
duration is what makes power really. having the valve open for longer gives a better power increase than having it open for the standard duration but wider. they usually go together of course, more lift and longer duration.
big lift does tend to batter lifters a bit, as well as the springs.
big lift does tend to batter lifters a bit, as well as the springs.
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