pre-load/lash adjustments
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
This is probably best explained with a picture as well.
Here is a generalization:
Imagine a hydraulic lifter with 0.020" pre-load. As the lifter cycles, the seat
may move, pump-up, valve float/bouce, etc.
If the seat travels toward the top it will cause an early lift on the valve.
The less the seat moves (tighter pre-load), the less effect this will have.
Here is a generalization:
Imagine a hydraulic lifter with 0.020" pre-load. As the lifter cycles, the seat
may move, pump-up, valve float/bouce, etc.
If the seat travels toward the top it will cause an early lift on the valve.
The less the seat moves (tighter pre-load), the less effect this will have.
Thread Starter
TECH Enthusiast
Joined: May 2006
Posts: 631
Likes: 0
From: Metairie, LA
So, is it good or bad to have tight pre load on a hydraulic set up. I image, especially on an engine that will not see 6500 rpms and up, tight pre-load would be a good thing. Help prevent valve float, correct??
Originally Posted by eLTwerker
This just came up on the cam overlap thread. Didn't want to thread jack. So, what is this and how does it change overlap?
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
Originally Posted by brad8266
Preload has no effect on overlap as long as all lifters are preloaded the same, which they should be.
Have a read about 3/4 down the page under the "100 lashes" heading:
http://www.nhra.com/dragster/1999/is...echnology.html
I've done some valve settings on a few motors and notice improved vacuum
at idle as well as some extra HP on the dyno with my car.
It's a cool little trick.
Originally Posted by Adrenaline_Z
You might want to re-think that a touch.
Have a read about 3/4 down the page under the "100 lashes" heading:
http://www.nhra.com/dragster/1999/is...echnology.html
I've done some valve settings on a few motors and notice improved vacuum
at idle as well as some extra HP on the dyno with my car.
It's a cool little trick.
Have a read about 3/4 down the page under the "100 lashes" heading:
http://www.nhra.com/dragster/1999/is...echnology.html
I've done some valve settings on a few motors and notice improved vacuum
at idle as well as some extra HP on the dyno with my car.
It's a cool little trick.
Kill the Messenger!
Originally Posted by Adrenaline_Z
You might want to re-think that a touch.
Have a read about 3/4 down the page under the "100 lashes" heading:
http://www.nhra.com/dragster/1999/is...echnology.html
I've done some valve settings on a few motors and notice improved vacuum
at idle as well as some extra HP on the dyno with my car.
It's a cool little trick.
Have a read about 3/4 down the page under the "100 lashes" heading:
http://www.nhra.com/dragster/1999/is...echnology.html
I've done some valve settings on a few motors and notice improved vacuum
at idle as well as some extra HP on the dyno with my car.
It's a cool little trick.
100 lashes
"Most mechanical cams have some room for lash adjustment. A larger lash figure reduces the valve lift and duration. Adding lash opens the valve later, lifts it less, and closes it sooner, which in turn can help tame a wild camshaft. Removing lash from the published specification does just the opposite."
Originally Posted by brad8266
Oh ok, I get it.
Originally Posted by great421
Now, for the solid lifter crowd, I will conceed that rocker arm clearances (i.e - "valve lash") can indeed impact when a valve begins to move, but this is not the intended / primary function of valve lash; the clearance is there to allow for the thermal expansion of the materials involved, not to modify when the valves start to open.
