Question on LS7 lifter preload and Pushrod length.
01-11-2017, 08:56 PM
#32
the comp video wasn't available earlier when I was replying. maybe it was blocked from work? I dunno. basically their answer is "somewhere between 1 and 2 turns is OK".
like I said earlier, hydraulic lifters are forgiving, but why waste your time guessing when a $20 pushrod checker will tell you exactly what you need without guess work?
for example, what happens when you run an aftermarket casting heads with the valvetrain geometry changed? between 1 and 2 turns is too much of a variable for me. especially since I don't have 3 different pushrods to try out to see which guess works out best.
like I said earlier, hydraulic lifters are forgiving, but why waste your time guessing when a $20 pushrod checker will tell you exactly what you need without guess work?
for example, what happens when you run an aftermarket casting heads with the valvetrain geometry changed? between 1 and 2 turns is too much of a variable for me. especially since I don't have 3 different pushrods to try out to see which guess works out best.
01-11-2017, 10:51 PM
#33
Launching!
Thread Starter
When you say that "Between 1 and 1-3/4 turns" is to much variable to you. You do know that you have control of that variable right? It all depends and what preload you desire. If each 360 degree turn is 0.047 preload, then 1/2 a turn is 0.0235 preload, and each 1/4 turn is 0.01175 preload and 2 turns is 0.094 preload. Do you understand what I mean? So if you want, say...around 0.130 preload with your stock lifters, and you know that 1 turn is equal to 0.047 of preload, then 3 full turns is 0.141 preload. So you realise you need less turns, so after all the math, 2-3/4 turns is 0.12925 of preload. Now all this is at 22 ft lbs and the controling variable would be the adjustable pushrod.
What the video is saying is that between 1 and 1-3/4 turns, which is 0.047 through 0.08225 of preload. When I talked to COMP by email, they said with standard lifters and a stock rocker bolt, such as LS7 lifters, that when you hit 0 lash (using the adjustable pushrod set at your desired length) that each full 360 degree turn of the torque wrench is equal to 0.047 preload. Now since GM recommends up to 0.090 preload and down to 0.040 or whatever depending on the application, I assume that is why they say between 1 and 1-3/4 turns. They recommended this method to me, sent me the video, and said to do it that way. This is why I assumed this is the common method that everyone uses to get the correct preload on their lifters.
Now I have 2 different Pushrod length checkers, a COMP Cams 6.800"-7.800" and each full turn is equal to 0.050" length, and another one which I do not know the brand and what is full turn represents so I did not use that one.
In my GM Tech manual, which is just an 500+ page Adobe file on my computer, tells me that in my application that the LS7 lifters I am using should be set between 0.071 and 0.091 of preload.
So when you say guess work, I really didn't think that this is "guess work" since it is a process that seems pretty accurate and is actually simple. The "between 1 and 1-3/4 turns", as said in the video is for stock applications with an aftermarket cam and can be between 50-60 turns or whatever you want your preload to be set between, it can be 1/2-3/4 turns(which is 0.0235-0.03525 of preload). Say your Lifter manufacturer recommends as close to 0.020 of preload, then the same process applies, and using the turn method and doing simple math, getting 22 ft lbs at 1/2 turn is equal to 0.0235 preload. So you just use your adjustable pushrod and start with a common length such as 7.400" and if you get 22ft lbs and 3 full turns, then you know your pushrod is way to long, and you shorten up the adjustable pushrod and try again, so maybe move down to 7.300, and you do not need 3 different pushrod lengths like you said, just the adjustable pushrod.
I hope this makes since and you now see why I used this method. I really do not see this as "guess work" as you put it. Especially since a company like COMP Cams said to use.
If someone would of told me "Hey man, there is a better method than the one you are using. Just find the base circle of the cam for the location you are trying to measure, then put the adjustable pushrod in and set it at 0 turns, then torque down the rocker arm bolt to 22 ft lbs, then adjust the adjustable pushrod until it just barley touches the rocker arm (Which is 0 Lash) and be careful not to adjust it to far or it will start adding preload to the lifter. Once you hit 0 lash, remove the rocker arm and bolt and go ahead and measure that pushrod, then once you figure out that length (Example: 7.270") go ahead and add your desired preload to the length of that pushrod you just measured (Example: 7.270"+0.080 Preload = 7.350" Desired pushrod length). Then it would be best to measure all 16 to make sure they are all close to the same length needed. Then heck, I would of done that right away. But COMP Cams told me to do it that way and you guys say I am making this to Complex or I am fixated on this method and what not.
What the video is saying is that between 1 and 1-3/4 turns, which is 0.047 through 0.08225 of preload. When I talked to COMP by email, they said with standard lifters and a stock rocker bolt, such as LS7 lifters, that when you hit 0 lash (using the adjustable pushrod set at your desired length) that each full 360 degree turn of the torque wrench is equal to 0.047 preload. Now since GM recommends up to 0.090 preload and down to 0.040 or whatever depending on the application, I assume that is why they say between 1 and 1-3/4 turns. They recommended this method to me, sent me the video, and said to do it that way. This is why I assumed this is the common method that everyone uses to get the correct preload on their lifters.
Now I have 2 different Pushrod length checkers, a COMP Cams 6.800"-7.800" and each full turn is equal to 0.050" length, and another one which I do not know the brand and what is full turn represents so I did not use that one.
In my GM Tech manual, which is just an 500+ page Adobe file on my computer, tells me that in my application that the LS7 lifters I am using should be set between 0.071 and 0.091 of preload.
So when you say guess work, I really didn't think that this is "guess work" since it is a process that seems pretty accurate and is actually simple. The "between 1 and 1-3/4 turns", as said in the video is for stock applications with an aftermarket cam and can be between 50-60 turns or whatever you want your preload to be set between, it can be 1/2-3/4 turns(which is 0.0235-0.03525 of preload). Say your Lifter manufacturer recommends as close to 0.020 of preload, then the same process applies, and using the turn method and doing simple math, getting 22 ft lbs at 1/2 turn is equal to 0.0235 preload. So you just use your adjustable pushrod and start with a common length such as 7.400" and if you get 22ft lbs and 3 full turns, then you know your pushrod is way to long, and you shorten up the adjustable pushrod and try again, so maybe move down to 7.300, and you do not need 3 different pushrod lengths like you said, just the adjustable pushrod.
I hope this makes since and you now see why I used this method. I really do not see this as "guess work" as you put it. Especially since a company like COMP Cams said to use.
If someone would of told me "Hey man, there is a better method than the one you are using. Just find the base circle of the cam for the location you are trying to measure, then put the adjustable pushrod in and set it at 0 turns, then torque down the rocker arm bolt to 22 ft lbs, then adjust the adjustable pushrod until it just barley touches the rocker arm (Which is 0 Lash) and be careful not to adjust it to far or it will start adding preload to the lifter. Once you hit 0 lash, remove the rocker arm and bolt and go ahead and measure that pushrod, then once you figure out that length (Example: 7.270") go ahead and add your desired preload to the length of that pushrod you just measured (Example: 7.270"+0.080 Preload = 7.350" Desired pushrod length). Then it would be best to measure all 16 to make sure they are all close to the same length needed. Then heck, I would of done that right away. But COMP Cams told me to do it that way and you guys say I am making this to Complex or I am fixated on this method and what not.
Last edited by 07NBSChevy; 01-11-2017 at 11:01 PM.
01-12-2017, 05:19 AM
#36
If someone would of told me "Hey man, there is a better method than the one you are using. Just find the base circle of the cam for the location you are trying to measure, then put the adjustable pushrod in and set it at 0 turns, then torque down the rocker arm bolt to 22 ft lbs, then adjust the adjustable pushrod until it just barley touches the rocker arm (Which is 0 Lash) and be careful not to adjust it to far or it will start adding preload to the lifter. Once you hit 0 lash, remove the rocker arm and bolt and go ahead and measure that pushrod, then once you figure out that length (Example: 7.270") go ahead and add your desired preload to the length of that pushrod you just measured (Example: 7.270"+0.080 Preload = 7.350" Desired pushrod length).
01-15-2017, 05:04 AM
#37
Launching!
Thread Starter
Thanks for the reply. I also realized that I mis-counted the turns when trying to find 0 lash. It was a yad over 9 turns. But anyway I needed 7.325" pushrod and they just came in from BTR. I also ordered 7.350" so see how they measure up once their in.
Another thing was I actually measured the stock pushrods and they are 7.375" and not 7.4 like I was told. Just waiting for good weather to get the motor installed. I cant wait to get the truck back up and running again, it has been 4 months waiting on parts, money and time to do everything.
Another thing was I actually measured the stock pushrods and they are 7.375" and not 7.4 like I was told. Just waiting for good weather to get the motor installed. I cant wait to get the truck back up and running again, it has been 4 months waiting on parts, money and time to do everything.
Last edited by 07NBSChevy; 01-19-2017 at 07:56 PM.
01-19-2017, 01:26 AM
#38
Launching!
Thread Starter
Quick Question guys, I have on hand 7.350 and 7.325 pushrods. I have also verified that stock pushrods are 7.375" long. On all 16 valves, I have checked that 9-1/8 thru 9-1/4 turns will net me 0 Lash.
So by the looks of it from above, this is using the turns to 0 Lash method, using 7.350 pushrods should net me around 0.090 of preload and using 7.325" pushrods should net me around 0.065 of preload. Which preload would be a better option?
So by the looks of it from above, this is using the turns to 0 Lash method, using 7.350 pushrods should net me around 0.090 of preload and using 7.325" pushrods should net me around 0.065 of preload. Which preload would be a better option?
Last edited by 07NBSChevy; 01-19-2017 at 07:53 PM.
01-19-2017, 07:47 PM
#40
Launching!
Thread Starter
I could of said "which is better, 0.065 or 0.090 preload" but I thought I would update some stuff from before.
But sure thanks, for not providing any answer to the question.
But sure thanks, for not providing any answer to the question.
Last edited by 07NBSChevy; 01-19-2017 at 07:53 PM.