LS Valve Train Noise Sucks! I challenge the aftermarket.
02-18-2012, 05:10 PM
#82
I just pulled my front cover off to change my cam timing a bit and I was really hoping I would find something wrong with my oil pump o-ring. I was dreaming that it was sucking some air and causing my problem and that replacing the o-ring would render my valve train silent. Then I woke up. The o-ring was perfect. 
02-18-2012, 09:48 PM
#83
I just pulled my front cover off to change my cam timing a bit and I was really hoping I would find something wrong with my oil pump o-ring. I was dreaming that it was sucking some air and causing my problem and that replacing the o-ring would render my valve train silent. Then I woke up. The o-ring was perfect.
03-20-2012, 10:34 PM
#84
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I recently have been trying to figure out pushrods for my setup and came to the conclusion that 1/4 turn equals .017 preload so from zero lash to 24ft lbs should be right at 1 turn to equal around .050 preload. I find it hard to believe that a lifter would need more preload than that because when the lifter is full of oil running at 60+psi at say 4000 rpm the lifters wont let the valves close completely putting you down on compression and power.
But I dont know everything but it makes perfect sense to me.
My setup is a stock ls1 with ls7 lifters, 243 heads, gm mls gaskets and a torquer v2 cam and I will end up needing a 7.350 pushrod verified by using a tsp 7.4 pushrod and a dial indicator.
But I dont know everything but it makes perfect sense to me.
My setup is a stock ls1 with ls7 lifters, 243 heads, gm mls gaskets and a torquer v2 cam and I will end up needing a 7.350 pushrod verified by using a tsp 7.4 pushrod and a dial indicator.
03-20-2012, 11:06 PM
#85
I do agree with you 1 turn to 22 ft-lbs is ~0.050" pre-load.
If you want the whole story go to this thread:
https://ls1tech.com/forums/generatio...-pre-load.html
And look at this post:
https://ls1tech.com/forums/16048763-post41.html
I think it depends on what lifters you are using and what the total plunger travel is.
03-21-2012, 11:07 PM
#86
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[QUOTE=ZeeOSix;16104691]It takes ~1/3 of a turn to just torque the bolt from 0 to 22 ft-lbs without moving anything ... so not sure why you say 0.017 with 1/4 turn to 22 ft-lbs.
I do agree with you 1 turn to 22 ft-lbs is ~0.050" pre-load.
If you put a dial indicator on top of the rocker arm directly above the pushrod at zero lash and turn the bolt .25 of a turn the rocker preloads the lifter .017 per my checking. Therefore .75 of a turn would equal .051 preload plus another .25 of a turn to reach 22 ft-lbs.
I do agree with you 1 turn to 22 ft-lbs is ~0.050" pre-load.
If you put a dial indicator on top of the rocker arm directly above the pushrod at zero lash and turn the bolt .25 of a turn the rocker preloads the lifter .017 per my checking. Therefore .75 of a turn would equal .051 preload plus another .25 of a turn to reach 22 ft-lbs.
03-22-2012, 03:25 AM
#87
If you put a dial indicator on top of the rocker arm directly above the pushrod at zero lash and turn the bolt .25 of a turn the rocker preloads the lifter .017 per my checking. Therefore .75 of a turn would equal .051 preload plus another .25 of a turn to reach 22 ft-lbs.
Therefore, (0.75 - 0.333) x 0.049 x (2.7/1.7) = 0.032"
Total pre-load for 1 turn is therefore 0.019 + 0.032 = 0.051".
The links I gave in post #85 shows how these formulas were derived.
05-10-2012, 02:07 AM
#89
Adjustable rockers are only really needed when running a solid lifter. Using them in conjunction with a hydraulic lifter adds complication and possible valve cover clearance issues. If you are however very picky and say want exactly a specific preload then an adjustable rocker is the only way as push rods only come in .025" increments from what I have seen.
Either way most lifters have an operating range greater than .025" so adjustable isn't needed.
I know that I personally have a lot of valve noise as I can hear it from the reflection off a car or tall curb.... Using the turn method I get .086" int and .090" exh preload with 7.425" push rods. I also have tried 7.4" pushrods and the noise is almost identical. I am going to have to look into a different lobe I think. My rockers aren't tight if I rotate the engine and the lifter is resting on the base circle. :-( Maybe they aren't pumping up enough. If I remove the rocker and let it sit for 5 min then bolt is back down it is tight again.
Either way most lifters have an operating range greater than .025" so adjustable isn't needed.
I know that I personally have a lot of valve noise as I can hear it from the reflection off a car or tall curb.... Using the turn method I get .086" int and .090" exh preload with 7.425" push rods. I also have tried 7.4" pushrods and the noise is almost identical. I am going to have to look into a different lobe I think. My rockers aren't tight if I rotate the engine and the lifter is resting on the base circle. :-( Maybe they aren't pumping up enough. If I remove the rocker and let it sit for 5 min then bolt is back down it is tight again.
05-10-2012, 02:49 AM
#90
LS7 lifters are 'NOT' taller!!!!!
I had sewing machine when I went cam only & stayed with 7.4 pushrods....As has been stated..'attention to detail'. Now with shaved heads, higher comp, different cam etc etc & better attention to detail, & a Fast intake I have a relatively quiet valve train.
edit: Just noticed you listed comp trunion upgrade. Just maybe you need adj r/rockers to get your valve train quiet, good quality shaft mounted Jessels.
I had sewing machine when I went cam only & stayed with 7.4 pushrods....As has been stated..'attention to detail'. Now with shaved heads, higher comp, different cam etc etc & better attention to detail, & a Fast intake I have a relatively quiet valve train.
edit: Just noticed you listed comp trunion upgrade. Just maybe you need adj r/rockers to get your valve train quiet, good quality shaft mounted Jessels.
does anyone have experience with these comp shaft rockers and the rpm rating for them? my ls6 is kinda noise with the XE R cam i have ,, and plan on going with trickflow 215cc heads or with PRCs new 227 3.9 bore head,,
thanks fellas
05-10-2012, 03:04 AM
#91
There is only one proper way to measure preload. Put the cam on the base circle, install a lifter and adjustable pushrod. Torque the rocker into place, then lengthen the pushrod to zero lash. Remove, the rocker, measure the pushrod, add the amount of preload you desire to that length, and order it.
and measure all of them as stated by BADD SS
good post this is what i have seen others do and works ,,
can someone help regarding the post by me above this one on the rockers noise and stability,,
05-10-2012, 09:08 AM
#92
Actually, I'm going to disagree with that. If you are going to upgrade your rockers anyway, you might as well get something like Lunati has. If I remember correctly, their rocker adjusts the cup. I really like that style. It should allow some changes to the geometry of the system that Polylocks may not.
06-15-2012, 03:54 PM
#93
I like this I think the whole lifter preload issue has been beaten to death here. GM's spec is .055"-.085" preload. I normally recommend the lower end of this for best performance and the least noise. I run cams from mild to wild and as long as the springs are shimmed properly and the correct preload settings are used, valvetrain noise should be minimal. Header material and intake manifold material play a huge part here as well but if the valvetrain is set up correctly, the root cause of the noise is minimized.
FWIW, I had an LSK lobed cam in my '05 CTS-V for 25K+ miles. For the first 10K I had a stock LS6 manifold. With 26921 springs shimmed for .637" lift (.015"), .050" preload, stock rockers and double Jet Hot coated Kooks 1 7/8" headers, the valvetrain noise was almost non-existant. When I switched to the FAST 90 intake, I could hear every intake valve close individually. No sewing machine noise but with the hood open it sounded like someone was tapping on the inside of my intake manifold with a small hammer!
Now with my TRu-Torq L5 cam, (less lift, same duration on intake) I am noise free once again (same 921's re-shimmed for the lower lift) even though the closing rates are almost identical on both cam's intake lobes. My point is, most everyone here has forgotten a couple of the biggest factors which contribute to noise: valvespring choice/setup and the natural harmonics of that particular setup.
Thanks,
Shane
FWIW, I had an LSK lobed cam in my '05 CTS-V for 25K+ miles. For the first 10K I had a stock LS6 manifold. With 26921 springs shimmed for .637" lift (.015"), .050" preload, stock rockers and double Jet Hot coated Kooks 1 7/8" headers, the valvetrain noise was almost non-existant. When I switched to the FAST 90 intake, I could hear every intake valve close individually. No sewing machine noise but with the hood open it sounded like someone was tapping on the inside of my intake manifold with a small hammer!
Now with my TRu-Torq L5 cam, (less lift, same duration on intake) I am noise free once again (same 921's re-shimmed for the lower lift) even though the closing rates are almost identical on both cam's intake lobes. My point is, most everyone here has forgotten a couple of the biggest factors which contribute to noise: valvespring choice/setup and the natural harmonics of that particular setup.
Thanks,
Shane
10-31-2012, 08:09 AM
#94
TECH Enthusiast
I just pulled my front cover off to change my cam timing a bit and I was really hoping I would find something wrong with my oil pump o-ring. I was dreaming that it was sucking some air and causing my problem and that replacing the o-ring would render my valve train silent. Then I woke up. The o-ring was perfect.
Any update on the cam change and results yet ?
Thanks !
10-31-2012, 09:02 AM
#95
I just pulled my front cover off to change my cam timing a bit and I was really hoping I would find something wrong with my oil pump o-ring. I was dreaming that it was sucking some air and causing my problem and that replacing the o-ring would render my valve train silent. Then I woke up. The o-ring was perfect.
10-31-2012, 01:20 PM
#98
As long as the correct spring height And pushrods are determined and there is still noise just chock it up as "you gotta pay to play"...everyone's different setups have so many variables that the only way to determine what works and what doesn't is to do a vibration analysis on a sample of let's say 10 different setups and compare their natural frequencies, maybe this would show some type of "pattern"....I would really like to see on of the good tech magazines to do some various testing to show the harmonics by using strategically placed accelrometers. I'm sure GM did this testing their selves that's why the stock cams make pretty go power while still passing NVH testing requirements in order to try to target a broader customer base (old guys to young kids).
I would be very interested to see that because its usually baseline, add these parts, dyno, add more parts, dyno....that sort of stuff gets old after a while. I want to see them use their time to figure out the answer for a long time LS issue. With the new lt1 out it would serve them best to vary the range of testing on the "venerable" lol LS series.
I would be very interested to see that because its usually baseline, add these parts, dyno, add more parts, dyno....that sort of stuff gets old after a while. I want to see them use their time to figure out the answer for a long time LS issue. With the new lt1 out it would serve them best to vary the range of testing on the "venerable" lol LS series.
