LS Valve Train Noise Sucks! I challenge the aftermarket.
11-05-2011, 01:55 PM
#41
I'm giving you my results. Your mileage may vary. 
I truly believe it makes a difference with the cam and springs you are running. With my set up, reducing the preload made a huge difference. Still noisy mind you, but at least I'm not embarrassed by it any more.
I truly believe it makes a difference with the cam and springs you are running. With my set up, reducing the preload made a huge difference. Still noisy mind you, but at least I'm not embarrassed by it any more.
11-05-2011, 09:15 PM
#42
I have between .029 and .030 preload, a relatively huge cam, probably bigger than all in this thread, stock rockers w/trunions, ls7 lifters, 3/8" pushrods, and it's dead silent, and spins 7900 on the other end of the spectrum...
I never had a quiet valvetrain with .080+ preload.....
I never had a quiet valvetrain with .080+ preload.....
11-06-2011, 06:55 PM
#43
TECH Fanatic
I have between .029 and .030 preload, a relatively huge cam, probably bigger than all in this thread, stock rockers w/trunions, ls7 lifters, 3/8" pushrods, and it's dead silent, and spins 7900 on the other end of the spectrum...
I never had a quiet valvetrain with .080+ preload.....
I never had a quiet valvetrain with .080+ preload.....
11-16-2011, 09:41 PM
#46
LS1Tech Sponsor
Valvetrain noise I can't speak for all of the LS aftermarket but most aftermarket camshafts are not designed with valvetrain noise in mind. That is one of the design variables that we can mostly ignore in order to increase power over the production camshafts. If you want a really quiet camshaft, get an LSA camshaft. The opening and closing ramp rates on that camshaft are very gradual in order to obtain excellent idle noise quality for the target vehicle and customer.
If enough people complained about the noise, we (or others) might think a business case could be made for such a product and we might try to make a camshaft that improved power but was still close to as quiet as the OEM camshafts but since few people ask for that (most just want the power), that isn't a very viable design criteria for us at this time.
Even between the different OEM camshafts the valvetrain noise difference can be fairly noticeable (put a stock LS7 next to a stock LSA for example).
Obviously other things impact this too. Some manifolds transmit more noise than others. Removing the factory intake covers and coil covers can allow more noise to be transmitted. And other items can also make noise that can be confused for valvetrain noise - different injectors make different levels of noise that sometimes can be confused for valvetrain noise. And then the other big variable is the person hearing the noise - what is loud and objectionable to one person can be silent to another and be music to another.
If enough people complained about the noise, we (or others) might think a business case could be made for such a product and we might try to make a camshaft that improved power but was still close to as quiet as the OEM camshafts but since few people ask for that (most just want the power), that isn't a very viable design criteria for us at this time.
Even between the different OEM camshafts the valvetrain noise difference can be fairly noticeable (put a stock LS7 next to a stock LSA for example).
Obviously other things impact this too. Some manifolds transmit more noise than others. Removing the factory intake covers and coil covers can allow more noise to be transmitted. And other items can also make noise that can be confused for valvetrain noise - different injectors make different levels of noise that sometimes can be confused for valvetrain noise. And then the other big variable is the person hearing the noise - what is loud and objectionable to one person can be silent to another and be music to another.
All this excessive valve train noise on LS engines hydraulic rollers suck. Somebody needs to produce a lobe, lifter or combination of the two that is quiet. It is literally the only downside to the LS engine that I know of. I have no idea why there is not more attention paid to this issue.
Who is going to step up?
Who is going to step up?
11-17-2011, 08:29 AM
#48
Very well said Jason...and supports what I have said all along
buzb...if it were my engine, I would try for .035 preload into the lifter. No more than .050. But this is where you are going to get a lot of differing opinions. You should PROBABLY end up with 7.400 push rods as that is what was stock and I don't see anything there changing that. (unless you have LS6 243 heads with the longer valves or have surfaced the heads/block) But get an adjustable pushrod and do your homework to get it right.
buzb...if it were my engine, I would try for .035 preload into the lifter. No more than .050. But this is where you are going to get a lot of differing opinions. You should PROBABLY end up with 7.400 push rods as that is what was stock and I don't see anything there changing that. (unless you have LS6 243 heads with the longer valves or have surfaced the heads/block) But get an adjustable pushrod and do your homework to get it right.
11-17-2011, 08:43 AM
#49
Take what you read on here with a grain of salt, borrow or purchase a pushrod length checker and measure them.
I measured all 16 of my lifters, and have roughly 5 different length custom manton pushrods so all my lifters are preloaded exactly the same. You dont need to go that far but it was just an example. Not every setup, or valve to valve height will be the same. Mine might only be off by .005-.01 between them, but its enough to cause me to use different lengths...
11-17-2011, 09:17 AM
#50
The measure the preload method is problematic too. As we have discovered in other threads that not all the lifters have the same height. One thread claiming to dispel the "internet myth" that the LS7 lifters were taller cup to roller than the older LS1 lifter turned out to show that several very reputable sources with proven measurement methods effective showed that there are different height lifters produced over the years as oem for LS motors. So, the accepted proven pushrod length checkers and the "count the rocker bolt turns" method may not give you an optimum preload for quiet valvetrain either either.
11-17-2011, 09:25 AM
#51
The measure the preload method is problematic too. As we have discovered in other threads that not all the lifters have the same height. One thread claiming to dispel the "internet myth" that the LS7 lifters were taller cup to roller than the older LS1 lifter turned out to show that several very reputable sources with proven measurement methods effective showed that there are different height lifters produced over the years as oem for LS motors. So, the accepted proven pushrod length checkers and the "count the rocker bolt turns" method may not give you an optimum preload for quiet valvetrain either either.
Counting the turns is a poor way to check. Pushrod length checker, large digital caliper= easy.
11-17-2011, 09:51 AM
#53
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.
11-17-2011, 10:02 AM
#54
That question is problematic to answer if the lifter heights vary. If one OEM lifter is .040"-.050" taller than another OEM lifter from roller to cup it opens the door to a lot of questions. The first is that since the factory does not use any other pushrod length than the standard 7.385" then does that mean that the sweep area of the lifter plunger is longer to make up for the difference? If so, does that mean that set ups with that lifter will prefer a .120"-130" preload as opposed to the .080" preload that is commonly quoted?
There appears to be more going on with lifters than is being acknowledged and I speculate this is why some are getting noisy valvetrain even when following the commonly trusted procedures for measuring.
There appears to be more going on with lifters than is being acknowledged and I speculate this is why some are getting noisy valvetrain even when following the commonly trusted procedures for measuring.
11-17-2011, 01:19 PM
#55
That question is problematic to answer if the lifter heights vary. If one OEM lifter is .040"-.050" taller than another OEM lifter from roller to cup it opens the door to a lot of questions. The first is that since the factory does not use any other pushrod length than the standard 7.385" then does that mean that the sweep area of the lifter plunger is longer to make up for the difference? If so, does that mean that set ups with that lifter will prefer a .120"-130" preload as opposed to the .080" preload that is commonly quoted?
There appears to be more going on with lifters than is being acknowledged and I speculate this is why some are getting noisy valvetrain even when following the commonly trusted procedures for measuring.
There appears to be more going on with lifters than is being acknowledged and I speculate this is why some are getting noisy valvetrain even when following the commonly trusted procedures for measuring.
11-17-2011, 02:35 PM
#56
As mentioned in the other thread regarding the LS7 lifters, due to tolerance stack-up, you could technically need 16 different pushrods. I've seen a total deviation of +/- .050" on the LS7's. The 1 thing you have to remember in the manufacturing world is, nothing is exact, except it. With OEM lifters you see more fluctuation due to the high volumes and wider tolerances. Also, OE lifters like to run near the bottom of the "accepted" leakdown rate span. Not all of them, but many of them. The relationship of leakdown rates, piston travel, piston location, piston to body fit, and how round/straight/smooth the grinds are equal what kind of performance the lifter will have and for how long. Sometimes for better performance, the trade off is a noisy lifter. Nature of the beast but I'm also a fan of solid valve trains.
11-17-2011, 03:47 PM
#58
I think you are missing my point. It is not a cylinder to cylinder variation problem, but a batch to batch or production specification variation. And, again, you are saying that measuring will tell you the ideal preload will be determined by a simple measurement of any given pushrod. What I am saying is that if on lifter has a different height & a different lifter plunger travel length/depth, it may prefer or need a different preload to produce the quietest valve train. No need to be hostile. We are all friends here looking for solutions to our individual problems.
11-17-2011, 03:48 PM
#59
As mentioned in the other thread regarding the LS7 lifters, due to tolerance stack-up, you could technically need 16 different pushrods. I've seen a total deviation of +/- .050" on the LS7's. The 1 thing you have to remember in the manufacturing world is, nothing is exact, except it. With OEM lifters you see more fluctuation due to the high volumes and wider tolerances. Also, OE lifters like to run near the bottom of the "accepted" leakdown rate span. Not all of them, but many of them. The relationship of leakdown rates, piston travel, piston location, piston to body fit, and how round/straight/smooth the grinds are equal what kind of performance the lifter will have and for how long. Sometimes for better performance, the trade off is a noisy lifter. Nature of the beast but I'm also a fan of solid valve trains.
11-17-2011, 04:31 PM
#60
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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