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XE head question

998 views 30 replies 8 participants last post by  Brian_S 
#1 ·
What size are the standard inlet values?, also what is the largest size of inlet valve I can use and is it worth doing.

Thanx for the help
 
#5 ·
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
 
#6 ·
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.
 
#9 ·
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.
 
#10 ·
mininut said:
I assume that solid lifter would solve the noise and other problems related to the 420 - 450 cams then.

Also where on the exaust port is there a restriction??
What do you mean 420-450 cams?
It can't been duration bigger than 340-350.
The full cycle is 360 degrees.:confused:
 
#14 · (Edited)
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.
 
#15 ·
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
 
#16 ·
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.
 
#22 ·
cos the head aint coming off for a loooong time and the pistons sure as hell aint coming out to get machined. i dont have the time anymore to build the engine again. :(
these cams produce a fair amount of power and are used by a norwegian ice rally team. its gonna be up with the 215+ kit so why bother with all the hassle? i am just a lazy stoodent bum :p and for 150 quid they are a damn sight cheaper than the 215 cams anyway!
 
#23 ·
What about - I send you my pistons which are sat around doing nothing. You get them machined, crack head off and sump, undo rod bolts. Lift pistons up, remove from rod, and swap the pistons over, retaining old rings, pop back down holes. Do rod bolts up, pop head back on, and bobs yer uncle! lol

(don't forget to send you std pistons back to me!)

My engines way off needing pistons at the moment ;)

( *hard hat on for using old rings on different pistons! lol * )
 
#26 ·
hmm. would use new rings dude! and then rehone the bores (can you even do that safely with the crank etc in?)
its an idea tho, apart from i simply cant afford it mate, i am struggling to get 150 quid! plus the mot and tax are up next week & end of month :(

this way i get very nearly the same power and its a 10 minute job for 150 quid, it really does make bhp/£££ sense!
doing the 215 job would give me about 2-5bhp more and cost 5 times as much assuming you mean get even wilder cams which will cost me, or just the piston work and rings & rebuild bits would be over 150 alone and give me no gains over the standard.
this way i can also go for high comp intruders and adj pulleys for more torque at a later date.
plus theres the fact hardly anyone runs this setup so its a bit different innit
 
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