Pushrod length sanity check
Pushrod length sanity check Ever since I put my LQ4 back together (ported 853 heads, LS7 lifters, 210*/218* .551 lift on 116 LSA, and Comp 7.300 pushrods) I've had an unholy sewing machine noise. The engine runs strong, but is pretty noisy.
It seems to be the loudest on the passenger side of the engine.
This is far from a radical combo and feel it should sound near stock.
When using an adjustable pushrod, my measured (via caliper) pushrod length at zero lash was 7.230. An extra .050 for lifter preload would put me at 7.280. I ordered 7.300 and threw it all together. On startup it sounded pretty nasty, but started quieting down as the lifters pumped up. I have a steady and consistent knock that I feel is still coming from the valve train.
Once I started researching the issue, I've found people mentioning gauge length vs total length of a pushrod. Is the difference in gauge vs total length something that could have lead me to order the wrong pushrods?
Given the above info, what pushrod length would you suggest?
It seems to be the loudest on the passenger side of the engine.
This is far from a radical combo and feel it should sound near stock.
When using an adjustable pushrod, my measured (via caliper) pushrod length at zero lash was 7.230. An extra .050 for lifter preload would put me at 7.280. I ordered 7.300 and threw it all together. On startup it sounded pretty nasty, but started quieting down as the lifters pumped up. I have a steady and consistent knock that I feel is still coming from the valve train.
Once I started researching the issue, I've found people mentioning gauge length vs total length of a pushrod. Is the difference in gauge vs total length something that could have lead me to order the wrong pushrods?
Given the above info, what pushrod length would you suggest?
The difference between gauge length and actual length is about 0.0170 inch. So if you ordered Comp Cam 7.300 its actual length would have been 7.283. So your actual preload is about 0.053 inch.
The difference between these two definitions doesn't change the actual length, they are measurements of the same pushrod taken at two different locations. If your valve train is noisy, I would ask how you measured the first time to determine if you measured correctly.
A 7.300" gauge length would actually be 7.317" overall length with gauge length taken on the ball where it is 0.140" in diameter (more or less the contact patch with the pushrod cup) and overall length is the distance between the ends of the oil holes.
The difference between these two definitions doesn't change the actual length, they are measurements of the same pushrod taken at two different locations. If your valve train is noisy, I would ask how you measured the first time to determine if you measured correctly.
The difference between these two definitions doesn't change the actual length, they are measurements of the same pushrod taken at two different locations. If your valve train is noisy, I would ask how you measured the first time to determine if you measured correctly.
(In my case I measured using Comp Cams adjustable pushrod and determined a specific length to order. The problem was I ordered from Manton who is a "overall" length supplier. I came up short. Stated another way my Comp Cam adjustable pushrod, which is label 6.80 has an overall length of 6.817.)
I will be opening it back up to re-measure tomorrow. I just wanted to make sure I was correct in my math before going through the trouble again. It sounds as if the gauge length should have come out in my favor in this scenario, adding to my preload.
I would absolutely concur that I must have measured something incorrectly. IMO, the valve train sounds too loose. What's odd about it is that I had around 1 1/2 turns before I hit 22 lb/ft when doing the final torque on the rockers. I know each case is unique, but that seems to be similar to those who do end up with the proper length.
I will be opening it back up to re-measure tomorrow. I just wanted to make sure I was correct in my math before going through the trouble again. It sounds as if the gauge length should have come out in my favor in this scenario, adding to my preload.
I will be opening it back up to re-measure tomorrow. I just wanted to make sure I was correct in my math before going through the trouble again. It sounds as if the gauge length should have come out in my favor in this scenario, adding to my preload.
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I agree, 7.300" for that mild cam, something seems off. Use the EO/IC method for determining that your lifters are on the base circle and zero lash can be very hard to achieve. You can tighten the rocker bolt with your finger well past zero lash before feeling any resistance.
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If you are getting 1-1/2 turns that does sound odd. How are you determining zero lash? I never get it right using the old method of twisting the pushrod between my fingers. I gently lift the rocker tip until I get rid of any clearance or "tick" "tick" when I lift it. You have to be very gentle doing this though. Also, are you sure the lifter is on the base circle of the cam and all the way down. I have also found that if the pushrod is out and you move the motor the lifter will stay up in the lifter tray and you need to push it back down against the cam before measuring.
For cyl #1, the lifters are on the cam's base circle when both cam/crank dots are at 12 o'clock.
The EO/IC method is also accurate practice for finding the cam's base circle.
Last edited by Squirts11; Aug 27, 2010 at 09:30 AM.
IIRC the LS7 lifters do have the cups for the PR's up higher than the standard LS1 lifters, however I've heard it to be only .05" or so
I'm installing milled heads (TSP 5.3's down to 59cc) and the LS7 lifters and I'm anticipating needing 7.3" for my PR's once I throw it together.
I'm installing milled heads (TSP 5.3's down to 59cc) and the LS7 lifters and I'm anticipating needing 7.3" for my PR's once I throw it together.
I finally had a chance to open it back up and take a few more measurements. I think I had originally gotten my EO/IC switched and used EC/IO. That's what you get when rushing at the end of a long day.
I ended up with much different numbers this time. I broke out the adjustable pushrod set at 7.367 (total length) and ended up with 1 5/8 turns exhaust, just a hare shy of 2 turns intake. I'd feel comfortable calling it 1 7/8.
Measuring with my 7.3's and stock 7.4's I'm noticing a pretty consistent trend that the intake looks like it may need .025 shorter than the exhaust. Should I simply run 7.350's all the way around and run with the additional preload on the intake? Or should I get 7.350's for the exhaust and 7.0325's for the intake?
I did mention these were ported 853's, but neglected to mention they do also have aftermarket valves as well. They're Lloyd Elliot Stage 2 heads. Is it common to have to staggered push rod lengths to make up for valve differences? I'm guessing the intake valve stem is longer, or the valve is recessed in the head a little. The cam is .551 lift on both intake and exhaust. I'm not certain where else the difference could be coming from.
I ended up with much different numbers this time. I broke out the adjustable pushrod set at 7.367 (total length) and ended up with 1 5/8 turns exhaust, just a hare shy of 2 turns intake. I'd feel comfortable calling it 1 7/8.
Measuring with my 7.3's and stock 7.4's I'm noticing a pretty consistent trend that the intake looks like it may need .025 shorter than the exhaust. Should I simply run 7.350's all the way around and run with the additional preload on the intake? Or should I get 7.350's for the exhaust and 7.0325's for the intake?
I did mention these were ported 853's, but neglected to mention they do also have aftermarket valves as well. They're Lloyd Elliot Stage 2 heads. Is it common to have to staggered push rod lengths to make up for valve differences? I'm guessing the intake valve stem is longer, or the valve is recessed in the head a little. The cam is .551 lift on both intake and exhaust. I'm not certain where else the difference could be coming from.
Last edited by Rhino; Aug 29, 2010 at 06:29 PM.
Could be valve length or the way it is set in the head. A lot of guys run two different lengths. You could also order from Manton since you have good measurements. You may also be able to increase the OD to 11/32".
Thanks for the help, I really do appreciate it. I'm still not 100% sure how I botched the measurements up so bad the first time. This motor is in my DD Avalanche. I'll probably stick with the standard Comp's. They'll be plenty strong for this build. I'm using moderate spring pressure on a smallish cam. I can count on my hand the number of times it's been over 5k.
With 7.350 all the way around I'll have .076 preload on the exhaust, .088 on the intake. With 7.320 on the intake side, I'd be looking at .061 preload. At this point I'd like to err on the high side of preload if possible.
On a related note, I realize .050 is commonly referenced as the minimum preload, but what would optimal and maximum operational preload be with LS7 lifters? I keep seeing a max preload numbers between .100 to .150 thrown about, but haven't found anything that's a little more definite. A thread on hardcorels1 made reference to almost .200 before bottoming out and referenced info gleaned from Predator-Z stating that stock preload was in the .080 to .100 area. I take all that info with a grain of salt, but want to find as much info as I can to make an informed decision.
EDIT: After reading quite a few more threads, I'm going to run with the 7.350 all the way around. I've found info from multiple sources (vendors) stating the LS7 lifter can be noisy at or below .060 preload.
With 7.350 all the way around I'll have .076 preload on the exhaust, .088 on the intake. With 7.320 on the intake side, I'd be looking at .061 preload. At this point I'd like to err on the high side of preload if possible.
On a related note, I realize .050 is commonly referenced as the minimum preload, but what would optimal and maximum operational preload be with LS7 lifters? I keep seeing a max preload numbers between .100 to .150 thrown about, but haven't found anything that's a little more definite. A thread on hardcorels1 made reference to almost .200 before bottoming out and referenced info gleaned from Predator-Z stating that stock preload was in the .080 to .100 area. I take all that info with a grain of salt, but want to find as much info as I can to make an informed decision.
EDIT: After reading quite a few more threads, I'm going to run with the 7.350 all the way around. I've found info from multiple sources (vendors) stating the LS7 lifter can be noisy at or below .060 preload.
Last edited by Rhino; Aug 29, 2010 at 09:44 PM.
The .080-.100" is what the LS1 lifters use and good lord were mine noisy at .050" and .060" preload. Have them at .075" and .085" preload int and exh respectively and it is much quieter.
Well... I got the 7.350 pushrods in and I can say it's better, but not by much. I'm almost certain that this is valve train noise, but apparently I'm lacking in some fundamental area.
Again, it's the passenger side that is much louder than the drivers. I've swapped the rockers between bank 1 and 2 to insure it wasn't anything there. Anyone have any other insight as to what's going on here? The intake's ended up being a little tighter than I had expected, and are just at 2 turns preload.
w/ 7.300 push rods
http://www.youtube.com/watch?v=vI0emQAcegk
w/ 7.350 push rods
http://www.youtube.com/watch?v=ziH1Y1KUUkw
Again, it's the passenger side that is much louder than the drivers. I've swapped the rockers between bank 1 and 2 to insure it wasn't anything there. Anyone have any other insight as to what's going on here? The intake's ended up being a little tighter than I had expected, and are just at 2 turns preload.
w/ 7.300 push rods
http://www.youtube.com/watch?v=vI0emQAcegk
w/ 7.350 push rods
http://www.youtube.com/watch?v=ziH1Y1KUUkw
Last edited by Rhino; Sep 4, 2010 at 11:57 AM.
It's absolutely not an exhaust leak. It's very mechanical in nature. Given the frequency in comparison with engine RPM, I'm almost certain it's in the valve train.
I have also tried two different sets of header gaskets. I had a set of paper gaskets when the engine was first installed; I've since moved to a set of good stainless steel gaskets with the same noise.
I have also tried two different sets of header gaskets. I had a set of paper gaskets when the engine was first installed; I've since moved to a set of good stainless steel gaskets with the same noise.
What cam lobe is it (XER)?
There was a post within the past few days where someone couldn't correct their noise (it was a shop) and finally went to a different cam with a different lobe, problem went away. You may want to contact them. Here is a link: Link
There was a post within the past few days where someone couldn't correct their noise (it was a shop) and finally went to a different cam with a different lobe, problem went away. You may want to contact them. Here is a link: Link