perload question
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From: new orleans, la
perload question im running prc 5.3 2.5 and an ms3 w/gm mls head gaskits
1. im using the shane from tr method of measuring perload he said run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
so is this wiggling side to side or up and down?
2. now i installed 7.350 push rods and went a little less the 1 1/4 turns. then installed 7.375 pushrods a went a little less then 1 1/2 turn. so the question is what does
.025 equal in how much more you can turn the bolt i.e
.025= a 1/4 turn
1. im using the shane from tr method of measuring perload he said run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
so is this wiggling side to side or up and down?
2. now i installed 7.350 push rods and went a little less the 1 1/4 turns. then installed 7.375 pushrods a went a little less then 1 1/2 turn. so the question is what does
.025 equal in how much more you can turn the bolt i.e
.025= a 1/4 turn
Here is how it works based on my method and Shane's method, both of which yield the same results (I checked) but understanding what is happening is important. As you turn the bolt, each revolution is 1.25mm or 0.049". However, the bolt is at the fulcrum so you have to take into account the rocker ratio. So each turn of the bolt at the pushrod results in 0.049" X 2.7/1.7 = 0.078". When using Shane's method, he states that one turn from zero lash to 22 lb-ft is 0.047" (or close to that, don't remember his exact number). However, when you tighten from zero lash to 22 lb-ft, the rocker will move down until it bottoms in the aluminum pedestal and any further tightening of the bolt doesn't move the rocker, or in other words, doesn't develop preload. When I checked his method, I found that from zero lash to the rocker bottoming was 5/8 turn and then it required a further 1/3 turn to develop 22 lb-ft. So using the 5/8 turn and my math, you get:
5/8 X (1.25/25.4) X (2.7/1.7) = 0.049" (Both methods yield the same result)
Now here is the difference, the 1/3 turn required to tighten the bolt doesn't change. So lets say instead of 1 turn you have 1-1/3 turns, then subtract the 1/3 turn for the bolt tightening after the rocker bottoms and you end up with 0.078" of preload. You can't just scale the values that Shane provides with one turn, however the error developed isn't huge.
As far as "wiggling" the rocker to find zero lash, I like to gently lift the rocker tip listening for a "tick" "tick" sound. Once that sound disappears you are at zero lash.
By my numbers your 1-1/4 turns is 0.072" and the 1-1/2 turns is 0.091" of preload.
5/8 X (1.25/25.4) X (2.7/1.7) = 0.049" (Both methods yield the same result)
Now here is the difference, the 1/3 turn required to tighten the bolt doesn't change. So lets say instead of 1 turn you have 1-1/3 turns, then subtract the 1/3 turn for the bolt tightening after the rocker bottoms and you end up with 0.078" of preload. You can't just scale the values that Shane provides with one turn, however the error developed isn't huge.
As far as "wiggling" the rocker to find zero lash, I like to gently lift the rocker tip listening for a "tick" "tick" sound. Once that sound disappears you are at zero lash.
By my numbers your 1-1/4 turns is 0.072" and the 1-1/2 turns is 0.091" of preload.
Here is how it works based on my method and Shane's method, both of which yield the same results (I checked) but understanding what is happening is important. As you turn the bolt, each revolution is 1.25mm or 0.049". However, the bolt is at the fulcrum so you have to take into account the rocker ratio. So each turn of the bolt at the pushrod results in 0.049" X 2.7/1.7 = 0.078". When using Shane's method, he states that one turn from zero lash to 22 lb-ft is 0.047" (or close to that, don't remember his exact number). However, when you tighten from zero lash to 22 lb-ft, the rocker will move down until it bottoms in the aluminum pedestal and any further tightening of the bolt doesn't move the rocker, or in other words, doesn't develop preload. When I checked his method, I found that from zero lash to the rocker bottoming was 5/8 turn and then it required a further 1/3 turn to develop 22 lb-ft. So using the 5/8 turn and my math, you get:
5/8 X (1.25/25.4) X (2.7/1.7) = 0.049" (Both methods yield the same result)
Now here is the difference, the 1/3 turn required to tighten the bolt doesn't change. So lets say instead of 1 turn you have 1-1/3 turns, then subtract the 1/3 turn for the bolt tightening after the rocker bottoms and you end up with 0.078" of preload. You can't just scale the values that Shane provides with one turn, however the error developed isn't huge.
As far as "wiggling" the rocker to find zero lash, I like to gently lift the rocker tip listening for a "tick" "tick" sound. Once that sound disappears you are at zero lash.
By my numbers your 1-1/4 turns is 0.072" and the 1-1/2 turns is 0.091" of preload.
5/8 X (1.25/25.4) X (2.7/1.7) = 0.049" (Both methods yield the same result)
Now here is the difference, the 1/3 turn required to tighten the bolt doesn't change. So lets say instead of 1 turn you have 1-1/3 turns, then subtract the 1/3 turn for the bolt tightening after the rocker bottoms and you end up with 0.078" of preload. You can't just scale the values that Shane provides with one turn, however the error developed isn't huge.
As far as "wiggling" the rocker to find zero lash, I like to gently lift the rocker tip listening for a "tick" "tick" sound. Once that sound disappears you are at zero lash.
By my numbers your 1-1/4 turns is 0.072" and the 1-1/2 turns is 0.091" of preload.
My .02
