entropy
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posted August 26, 2009 02:45 AM
 Edited By: entropy on 28 Aug 2009 18:07
lash w/head on the bench vs head on the motor, hmmm...
a couple nights ago i set valve lash w/head on the bench.
tonight i checked lash with head on the motor (motor on bench)
nearly every valve tightened up by about .001".
I have no idea why torquing the head on should tighten lash a lil bit.
any thoughts?????
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Y2KZX12R
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posted August 26, 2009 03:42 AM
Interesting.
Must be some kind of distortion of the cylinder heads cam tunnels under torque???
I guess you would need to measure rotating torque of the cams without the springs, buckets, valves etc. in the head. and then torque it down and remeasure the rotating torque to see if there is some tunnel distortion.
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entropy
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posted August 26, 2009 03:57 AM
I have torqued the cam caps over the cams (no valves) w/head on the bench and they spun freely. I have not tried the same thing with head bolted on the motor.
This is a brand new head, only been ported by you and seasts by Andy.
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Y2KZX12R
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posted August 26, 2009 04:37 AM
quote:
I have torqued the cam caps over the cams (no valves) w/head on the bench and they spun freely.
That's good, most builders skip this step or don't know to check the cams for straightness and excessive drag in the head. Bent cams can cost HP from drag and create excessive heat at the cam journals. And ALL weld up cams NEED to be checked in V blocks with a .0001" dial indicator!!!
It would be a good experiment to check the cam rotating torque with the head bolted on the block vs the bench.
Good observation Karl !!!
A little trick you can also do AFTER straightening the cams to within .001" is use dykem on the journals in the head and spin the cam so you can see any high spots. VERY lightly emery the high spots down. Then clean thoroughly and apply moly paste on the cam journals (not lobes) and spin ONE CAM at a time in the assembled head. Spin it about 50 times and the moly paste will embed in the journals in the head at any points of contact. Shush, don't tell anyone else!!!
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entropy
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posted August 26, 2009 04:43 AM
Thanks to TChin's advice (he knows how to stimulate the economy with my money), i have a full collection of shims in .001" increments and do strive for all int=.008, all exh = .011
I had that with head on the bench, but was flumoxed when i checked lash after mounting the head: WTF a buncha 7's and 10's, none of then went up in gap.
I thought temp, but the temp last night and the night the before last was very similar
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NOX
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posted August 26, 2009 06:17 AM
Karl, I had the same issue when I put my motor back together after lapping the valves, and resetting the lash.......
Stock original cams.....
They got about .001 tighter on the motor........
Good thread.
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entropy
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posted August 26, 2009 06:42 AM
quote:
Karl, I had the same issue when I put my motor back together after lapping the valves, and resetting the lash.......
Stock original cams.....
They got about .001 tighter on the motor........
Good thread.
hey Heath!
weird huh?
In June when I did the head on the bench, then checked lash with head on motor, i got the same issue, but i didn't track it carefully; i just thought i had done a shitty job on the bench
Glad we are seeing the same thing.
No damn idea why, but that's OK 
Karl
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ZRXDean
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posted August 26, 2009 07:21 AM
The 7-10 numbers are what I shoot for, is the 8-11 a KHI spec for the ZX12? Tighter lash = cheap lift & duration
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Shane661
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posted August 26, 2009 07:25 AM
Edited By: Shane661 on 26 Aug 2009 15:29
Could environmental temps affect this, as opposed to installation of the head?
EDIT: Nevermind...I guess you have considered this. Just seems very odd that all measurements would be affected equally, if it were due to distortion from the tightening process.
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entropy
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posted August 26, 2009 08:04 AM
quote:
The 7-10 numbers are what I shoot for, is the 8-11 a KHI spec for the ZX12? Tighter lash = cheap lift & duration
spec for 12 is int=6-9, exh =9-12
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tcchin
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posted August 26, 2009 08:34 AM
I have not seen this phenomenon on the GSX-R motors... Maybe it's a Kawasaki "feature". But .001" is a lot of deformation, especially since the cam tunnels are not in the head bolt load paths.
I blame those slutty Barbies!
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entropy
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posted August 26, 2009 09:46 AM
quote:
I have not seen this phenomenon on the GSX-R motors... Maybe it's a Kawasaki "feature". But .001" is a lot of deformation, especially since the cam tunnels are not in the head bolt load paths.
I blame those slutty Barbies!
Those dirty babies have been know to mess up my measurements in the past.
Tim may be onto something.
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WRECKSHOP
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posted August 26, 2009 09:55 AM
Wow, did not know that tighter lash gives you a little bit more lift and duration ?
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NOX
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posted August 26, 2009 01:49 PM
quote:
The 7-10 numbers are what I shoot for, is the 8-11 a KHI spec for the ZX12? Tighter lash = cheap lift & duration
I know nothing about this..........
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NOX
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posted August 26, 2009 01:50 PM
Also, mine could have been temp in the garage, as I set the lash on the bench on one day, then put it on, about 36 hours later......, in March...., I remember having to have a heater on at times.......
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Stuart Racing
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posted August 26, 2009 02:09 PM
I`ve heard some have built a plate with different bolt patterns for heads to actually torque a cyl. head to...To try to duplicate torquing to the motor and get precise valve lash.....
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krexken
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posted August 26, 2009 03:16 PM
.001! Come on!
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Johnnycheese
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posted August 26, 2009 03:23 PM
I always set the head .001 looser on the bench I thought because of oil.
but then again I was told to do this back in the 70's
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ZRXDean
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posted August 26, 2009 03:56 PM
quote:
.001! Come on!
This is Karl we're talking about here, don't act surprised.
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dougmeyer
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posted August 26, 2009 06:29 PM
This is new to me. Sometimes I have to change one or two, but I have never found a "consistent" change.
NOX- think about that for a while. What happens sooner and lasts longer when you have less lash?
D.
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tcchin
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posted August 26, 2009 06:46 PM
I think Doug's talking about the Barbies again...
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entropy
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posted August 26, 2009 08:10 PM
quote:
I think Doug's talking about the Barbies again...
score!!!
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NOX
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posted August 27, 2009 04:10 PM
quote:
This is new to me. Sometimes I have to change one or two, but I have never found a "consistent" change.
NOX- think about that for a while. What happens sooner and lasts longer when you have less lash?
D.
I know nothing...............LOL
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WRECKSHOP
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posted August 27, 2009 06:36 PM
Come on want you all elaborate on this subject matter and let the secrets out of the bag !!!!
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KZScott
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posted August 27, 2009 06:53 PM
think about the cam spinning, and hitting the bucket making it move. now picture the cam 1/4 in away. very exaggerated, but thats the idea. when its further away, it doesnt open it for as long, or for as far. much to be gained? i doubt its noticable. i shoot for 8-11, there are better ways to make power without being on the edge of a valve sticking open. unless you want to check lash every few weeks...
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