Manton pushrod length for 408
Thread Starter
On The Tree
Joined: Aug 2016
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Manton pushrod length for 408 So I just spent three days of reading and checking, and reading and re-checking my pushrod lengths for a 408 build. I'm a little curious because my measurements kept coming up longer than what most people said they were running in other posts. Maybe I overthought it, maybe not enough. Either way I ordered a set of 11/32 pr today from Manton at 7.462 OAL. Here's how I got that:
Using the standard Comp pushrod checker and the "turns of rocker bolt from zero lash to 22 ft lbs" method I got 12 turns on the gauge and roughly 1 1/4 turns on the rocker bolt (#1 intake using EO/IC method outlined elsewhere in the forum). I used this method on the remaining rockers, both intake and exhaust, and came up with ranges from just under 1 1/4 to just under 1 1/2. All within about a quarter turn of each other.
Using the Comp instructions, I got 6.8 + (12 x .050) = 7.4. Adding in .050 desired preload got me 7.45 for pr length. I called and had a great and informative conversation with Manton Pushrods. He advised me that the Comp checker is actually a little longer than advertised, and because of this he added .012 to the pushrods for a total, end to end, of 7.462.
Engine is a LQ4 block (stock deck), 317 heads (stock deck), Summit LS7 lifters, stock rockers with Straub trunions, Cam Motion cam, GM LS3 gaskets. For some reason that pr length seems a bit long compared to other builds on here, but I know most people say that every engine is it's own beast. Any input?
Using the standard Comp pushrod checker and the "turns of rocker bolt from zero lash to 22 ft lbs" method I got 12 turns on the gauge and roughly 1 1/4 turns on the rocker bolt (#1 intake using EO/IC method outlined elsewhere in the forum). I used this method on the remaining rockers, both intake and exhaust, and came up with ranges from just under 1 1/4 to just under 1 1/2. All within about a quarter turn of each other.
Using the Comp instructions, I got 6.8 + (12 x .050) = 7.4. Adding in .050 desired preload got me 7.45 for pr length. I called and had a great and informative conversation with Manton Pushrods. He advised me that the Comp checker is actually a little longer than advertised, and because of this he added .012 to the pushrods for a total, end to end, of 7.462.
Engine is a LQ4 block (stock deck), 317 heads (stock deck), Summit LS7 lifters, stock rockers with Straub trunions, Cam Motion cam, GM LS3 gaskets. For some reason that pr length seems a bit long compared to other builds on here, but I know most people say that every engine is it's own beast. Any input?
The adjustable pushrod uses gauge length to determine pushrod length. This length is measured from a point on the ball end where the ball is 0.140" in diameter. Not something you can easily measure. Manton uses overall lenght (OAL), which measures from end to end and includes the oil hole flatness and chamfer. This measurement is actually a bit less accurate, however given the accuracy of counting turns that is fine. The typical difference between the two measurements is 0.012" - 0.017".
What is really adding inaccuracy is that you are not measuring the pushrod length at zero lash and then adding your preload (at least based on your description). It sounds like you are setting pushrod length and then tightening the rocker to 22 lb-ft and counting rocker bolt turns. If that is the case then your pushrod measurements are off and you should really do them over by setting the pushrod length to just give zero lash with the bolt tightened.
What is really adding inaccuracy is that you are not measuring the pushrod length at zero lash and then adding your preload (at least based on your description). It sounds like you are setting pushrod length and then tightening the rocker to 22 lb-ft and counting rocker bolt turns. If that is the case then your pushrod measurements are off and you should really do them over by setting the pushrod length to just give zero lash with the bolt tightened.
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On The Tree
Joined: Aug 2016
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I used the EO/IC and bolt turn method I found in another thread here. Using a known PR length (the factory PR that were in this engine previously). Here's the basic steps I took:
1. I tightened the rocker bolt by hand until there was no "tick tick tick" when trying to move the rocker tip up and down on the valve stem. There was still lateral movement of the rocker arm, as it wasn't seated down fully on the pedestal.
2. I then tightened the rocker bolt to 22 ft lbs, counting turns. With factory PR it was between 1/2 and 3/4 turn to torque, indicating that I need a longer than factory PR.
3. I took the Comp gauge and adjusted it out 11 turns to get another known length, then repeated Step 2. Ultimately it took the Comp tool set at 12 turns out to allow 1 1/4 - 1 1/2 turns on the rocker bolt until torqued.
4. I took the known length of the gauge, 7.4, then added my desired preload of .05 for the total of 7.45. Manton added the extra .012 from gauge length to get the OAL number of 7.462.
Where in this did I miss the boat? I have a nagging feeling that I did somewhere, like maybe I combined two methods, or added preload a second time when I didn't need to. Should the rocker arm be fully seated in the pedestal to measure zero lash with the checker? My known length (factory) PR would not allow the rocker to seat fully on the pedestal unless I applied preload. Once I turned the gauge out it also wouldn't allow the rocker to seat down on the pedestal fully. I get that the "tick" should be gone, but should I be able to easily move the rocker side to side?
1. I tightened the rocker bolt by hand until there was no "tick tick tick" when trying to move the rocker tip up and down on the valve stem. There was still lateral movement of the rocker arm, as it wasn't seated down fully on the pedestal.
2. I then tightened the rocker bolt to 22 ft lbs, counting turns. With factory PR it was between 1/2 and 3/4 turn to torque, indicating that I need a longer than factory PR.
3. I took the Comp gauge and adjusted it out 11 turns to get another known length, then repeated Step 2. Ultimately it took the Comp tool set at 12 turns out to allow 1 1/4 - 1 1/2 turns on the rocker bolt until torqued.
4. I took the known length of the gauge, 7.4, then added my desired preload of .05 for the total of 7.45. Manton added the extra .012 from gauge length to get the OAL number of 7.462.
Where in this did I miss the boat? I have a nagging feeling that I did somewhere, like maybe I combined two methods, or added preload a second time when I didn't need to. Should the rocker arm be fully seated in the pedestal to measure zero lash with the checker? My known length (factory) PR would not allow the rocker to seat fully on the pedestal unless I applied preload. Once I turned the gauge out it also wouldn't allow the rocker to seat down on the pedestal fully. I get that the "tick" should be gone, but should I be able to easily move the rocker side to side?
Best way to measure pushrod length is to tape up the comp checker tool, install it with the lifter on the base circle and then put the rocker on the pedestal.
Make sure the rocker is fully seated in the pedestal. I used aftermarket bolts, so I would flip them over and push down on them to make sure the rocker wasn't moving. And then you adjust the PR Checker until there is no up and down play and the tick is gone. There should be very little side-to-side play if you are holding the trunnion pressed against the pedestal. At that point, you are at zero lash.
Now measure the total length with a digital caliper and add your desired preload to that value. This will give you the total length measurement that Manton uses.
Rinse repeat.
You can then set the PR checker to that length and torque down your rocker bolt and see if it gives you the desired number of turns (best with a torque wrench that gives you degrees as well so you can say 405 degrees vs 1-1/8 turn or whatever). That's a good check for it before ordering.
Make sure the rocker is fully seated in the pedestal. I used aftermarket bolts, so I would flip them over and push down on them to make sure the rocker wasn't moving. And then you adjust the PR Checker until there is no up and down play and the tick is gone. There should be very little side-to-side play if you are holding the trunnion pressed against the pedestal. At that point, you are at zero lash.
Now measure the total length with a digital caliper and add your desired preload to that value. This will give you the total length measurement that Manton uses.
Rinse repeat.
You can then set the PR checker to that length and torque down your rocker bolt and see if it gives you the desired number of turns (best with a torque wrench that gives you degrees as well so you can say 405 degrees vs 1-1/8 turn or whatever). That's a good check for it before ordering.
Thread Starter
On The Tree
Joined: Aug 2016
Posts: 130
Likes: 9
I went and rechecked everything this morning using vettenuts method. 10.5 turns left some lash, 11 turns preloaded the lifter very slightly. Using the 11 as my measurement I got this:
6.8 + (11 x .05) = 7.35. Add .05 desired lash = 7.4. Add Manton's .012 for gauge to actual difference = 7.412.
This sounds much more reasonable and doesn't combine the two methods, which is where I think I was going wrong. When I measured yesterday I think I inadvertently added an additional preload amount in my math because 7.412 plus an additional .05 lash gave me the 7.462. Guess I'll call and change the length before they cut them...
6.8 + (11 x .05) = 7.35. Add .05 desired lash = 7.4. Add Manton's .012 for gauge to actual difference = 7.412.
This sounds much more reasonable and doesn't combine the two methods, which is where I think I was going wrong. When I measured yesterday I think I inadvertently added an additional preload amount in my math because 7.412 plus an additional .05 lash gave me the 7.462. Guess I'll call and change the length before they cut them...
Thread Starter
On The Tree
Joined: Aug 2016
Posts: 130
Likes: 9
Best way to measure pushrod length is to tape up the comp checker tool, install it with the lifter on the base circle and then put the rocker on the pedestal.
Make sure the rocker is fully seated in the pedestal. I used aftermarket bolts, so I would flip them over and push down on them to make sure the rocker wasn't moving. And then you adjust the PR Checker until there is no up and down play and the tick is gone. There should be very little side-to-side play if you are holding the trunnion pressed against the pedestal. At that point, you are at zero lash.
Now measure the total length with a digital caliper and add your desired preload to that value. This will give you the total length measurement that Manton uses.
Rinse repeat.
You can then set the PR checker to that length and torque down your rocker bolt and see if it gives you the desired number of turns (best with a torque wrench that gives you degrees as well so you can say 405 degrees vs 1-1/8 turn or whatever). That's a good check for it before ordering.
Make sure the rocker is fully seated in the pedestal. I used aftermarket bolts, so I would flip them over and push down on them to make sure the rocker wasn't moving. And then you adjust the PR Checker until there is no up and down play and the tick is gone. There should be very little side-to-side play if you are holding the trunnion pressed against the pedestal. At that point, you are at zero lash.
Now measure the total length with a digital caliper and add your desired preload to that value. This will give you the total length measurement that Manton uses.
Rinse repeat.
You can then set the PR checker to that length and torque down your rocker bolt and see if it gives you the desired number of turns (best with a torque wrench that gives you degrees as well so you can say 405 degrees vs 1-1/8 turn or whatever). That's a good check for it before ordering.
It's not difficult. It's just time consuming. And it's hard to sometimes trust what the measurements tell you.
So, I say, take your time, double check or even triple check and then live with whatever your measurements say.
So, I say, take your time, double check or even triple check and then live with whatever your measurements say.
