pre-load/lash adjustments
01-12-2007, 10:43 PM
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pre-load/lash adjustments 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?
01-14-2007, 12:11 AM
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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.
01-14-2007, 01:03 AM
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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??
01-14-2007, 06:44 PM
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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?
01-14-2007, 09:07 PM
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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.
01-14-2007, 09:30 PM
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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.
01-31-2007, 11:01 AM
#7
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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.
