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Re: What's the point of valve lash ?
[Re: Stanton]
#836906
10/23/10 09:22 PM
10/23/10 09:22 PM
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Joined: Jan 2003
Posts: 10,035
Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,035
Frostbitefalls MN (Rocky&Bullw...
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A zero lash cam would have to much duration for best results. The valves would open too slow, and close too slow, allowing intake charge to escape or exhaust to escape too early and cut down on power. Thats why solid cams offer a bit more power than hydraulics, and roller cams are better yet. The best scenario would be instant open/instant close on the valves, but that isn't possible. Yet.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: What's the point of valve lash ?
[Re: tubtar]
#836907
10/23/10 09:26 PM
10/23/10 09:26 PM
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Joined: Jul 2010
Posts: 3,502
SOUTH JERSEY
HEMIFRED
master
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master
Joined: Jul 2010
Posts: 3,502
SOUTH JERSEY
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Valve lash is the clearance in the valve train between all the valve train parts to allow the full valve opening and also to make sure it closes all the way
home of the
Sox and Martin Hemi Duster
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Re: What's the point of valve lash ?
[Re: HEMIFRED]
#836908
10/23/10 09:30 PM
10/23/10 09:30 PM
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Joined: Jun 2007
Posts: 2,646
Plymouth Meeting, PA
bigtimeauto
Trophy Winner
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Trophy Winner
Joined: Jun 2007
Posts: 2,646
Plymouth Meeting, PA
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We run tight lash cams in the street cars and boat stuff. .010, You need some or with the engine temp change it will hang the valves open.
BB, TT5,Procharged 3300lb Street Car 4.79/154
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Re: What's the point of valve lash ?
[Re: gregsdart]
#836909
10/23/10 10:33 PM
10/23/10 10:33 PM
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Joined: May 2003
Posts: 6,571
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,571
Downtown Roebuck Ont
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Quote:
The best scenario would be instant open/instant close on the valves, but that isn't possible. Yet.
Actually it is "possible". A buddy of mine in the R+D biz says Honda has an engine with no cam that uses an ECM and solenoids or stepper motors to open/close the valves. Think of the possibilities, infinite cam timing changes on the fly so it can idle like a stocker and pull like a prostocker on the topside and everything in between. The wonders of modern technology  .
I can't even imagine the $$$$.
Kevin
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Re: What's the point of valve lash ?
[Re: Twostick]
#836910
10/23/10 11:43 PM
10/23/10 11:43 PM
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Joined: Oct 2005
Posts: 8,926
Ontario, Canada
Stanton
OP
Don't question me!
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OP
Don't question me!
Joined: Oct 2005
Posts: 8,926
Ontario, Canada
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Quote:
The best scenario would be instant open/instant close on the valves, but that isn't possible. Yet
Its possible but not desireable.
Keep in mind that the intake valve starts to open before the piston is at TDC and the exhaust valve is still open after TDC. A valve that opened instantly would spell disaster.
You could argue that that's a flaw with current technology HOWEVER, the overlap is a necessity in a normally aspirated motor as it is the exhaust flow that gets the intake charge moving. Remember, the exhaust is under pressure but the intake relies on atmosperic pressure to fill the cylinder.
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Re: What's the point of valve lash ?
[Re: gregsdart]
#836911
10/23/10 11:57 PM
10/23/10 11:57 PM
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Joined: Oct 2005
Posts: 8,926
Ontario, Canada
Stanton
OP
Don't question me!
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OP
Don't question me!
Joined: Oct 2005
Posts: 8,926
Ontario, Canada
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Quote:
A zero lash cam would have to much duration for best results.
Not true. All cam specs are based on the actual lobe, not the "after lash" measurement. Subsequently a .600" lift cam with .020" lash will only yeild .580" lift.
And more to your point, if lash is .020 then whatever the .050 duration spec is remains unchanged at the valve since the lash is already taken up before the .050 point. Only the "advertised" duration would be less at the valve after the lash adjustment.
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Re: What's the point of valve lash ?
[Re: Twostick]
#836914
10/24/10 01:07 AM
10/24/10 01:07 AM
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Joined: Oct 2007
Posts: 4,213
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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Actually it is "possible"
You'll know when that happens: all the parts break the first time.
Boffin Emeritus
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Re: What's the point of valve lash ?
[Re: polyspheric]
#836915
10/24/10 05:26 AM
10/24/10 05:26 AM
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Joined: Nov 2004
Posts: 7,274
s.w.fl
bonefish
master
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master
Joined: Nov 2004
Posts: 7,274
s.w.fl
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Quote:
Actually it is "possible"
You'll know when that happens: all the parts break the first time.
WHAT?THATS IT?THATS ALL? ARE YOU ILL?
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Re: What's the point of valve lash ?
[Re: Twostick]
#836917
10/24/10 05:36 AM
10/24/10 05:36 AM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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Quote:
Quote:
The best scenario would be instant open/instant close on the valves, but that isn't possible. Yet.
Actually it is "possible". A buddy of mine in the R+D biz says Honda has an engine with no cam that uses an ECM and solenoids or stepper motors to open/close the valves. Think of the possibilities, infinite cam timing changes on the fly so it can idle like a stocker and pull like a prostocker on the topside and everything in between. The wonders of modern technology .
I can't even imagine the $$$$.
Kevin
I've thought about that before! fully variable valve timing and lift! solenoids to open/close the valves. you could write a computer program to optimize power/torque at ANY rpm/throttle setting, or, fully shut down cylinders on the highway by just hanging the exhaust valve open so there's no power loss by a piston sucking down on a closed chamber, or pushing up on an empty one, yet not allow raw O2/gas to get sucked past the intake...
i wonder what a set-up like that would look like, and how much it would cost!
sure it sounds great, but then you'd lose that "high power lope" at idle that a radical high RPM cam gives you...it'd idle dead smooth with minimal overlap/duration at idle, yet hang them open as long as possible at higher RPMs for that top fueler scream.
**Photobucket sucks**
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Re:
[Re: HEMIFRED]
#836923
10/24/10 11:13 AM
10/24/10 11:13 AM
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Joined: Feb 2004
Posts: 6,257
acworth / N. georgia - south e...
cheapstreetdustr
master
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master
Joined: Feb 2004
Posts: 6,257
acworth / N. georgia - south e...
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i am gonna put my two cents in..
Valve lash is needed because of harmonics..
Ever struck a bell or plucked a guitar string?
same thing happens to the components in the valve train..
at high rpm everything looks like a wet noodle.
valve lash compensates for parts growing and or recoil..type effect..(equal and opposite reaction)
As to the selinoid valve operation..
its been designed and implemented for many yrs..
mosty in Diesel motors ...because they run at lower rpm..
the biggest draw back to the selinoid system is
rpm or duty cycle..the technology isnt there yet to open and close them at high rates
that is the issue with this tech that is problematic..and also why you will find them now only on diesel motors.
ive always said..use two intake valves and alternate which one opens. this would split the duty cycle in half.
that should atleast double the rpm range.
but i digress
cheapst
365" Iron J heads,,3480lbs best 1.39 60ft on SS springs.10.54,124 mph ...6.67 1/8th et.average 60fts 1.46 w/ small cam &.063 no2 pill tagged & insured
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