Intermittent noise after cam install
Thread Starter
Instructor
Joined: Jul 2017
Posts: 225
Likes: 18
From: San Antonio TX
Intermittent noise after cam install w/ video
2006 base w/ 148k miles.
had ls2 bald eagle cam, dual valve springs, new timing chain, gm oil pump, new 7.400 pushrods, etc installed and then they recommended I do lifters as well so ls7 lifters and ls9 headgaskets.
There is an intermittent tapping noise that comes and goes.
Shop that did the install said more valvetrain noise is normal. (This is not normal valvetrain noise)
My tuner (ton of ls experience) said it sounds like pushrods are wrong length and they are collapsing a lifter at certain rpm. I added thicker oil (5-40) to no avail.
so i bought a torque wrench and did the whole zero lash, count the turns to 22lbs thing and came up with 1.25 to 1.5 turns which is right where it should be, so now I am out of ideas.
There doesnt seem to be any rhyme or reason when it happens. It is not the normal sewing machine sound. It is more of a tapping like there is excessive play somewhere in the valve train. The fact that it comes and goes is what throws me.
Bad lifter maybe? I cant afford to bring it back to shop and have them troubleshoot. Trying to do as much as I can myself. It is my daily so cant be down too long
any ideas?
had ls2 bald eagle cam, dual valve springs, new timing chain, gm oil pump, new 7.400 pushrods, etc installed and then they recommended I do lifters as well so ls7 lifters and ls9 headgaskets.
There is an intermittent tapping noise that comes and goes.
Shop that did the install said more valvetrain noise is normal. (This is not normal valvetrain noise)
My tuner (ton of ls experience) said it sounds like pushrods are wrong length and they are collapsing a lifter at certain rpm. I added thicker oil (5-40) to no avail.
so i bought a torque wrench and did the whole zero lash, count the turns to 22lbs thing and came up with 1.25 to 1.5 turns which is right where it should be, so now I am out of ideas.
There doesnt seem to be any rhyme or reason when it happens. It is not the normal sewing machine sound. It is more of a tapping like there is excessive play somewhere in the valve train. The fact that it comes and goes is what throws me.
Bad lifter maybe? I cant afford to bring it back to shop and have them troubleshoot. Trying to do as much as I can myself. It is my daily so cant be down too long
any ideas?
Last edited by Huncle J; Nov 9, 2019 at 11:46 PM.
Safety Car
Joined: Aug 2017
Posts: 4,243
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From: North Myrtle Beach SC
Your gasket is .010 thinner. Multiply by rocker ratio 1.7 and you get .017 less clearance. Might need 7.375 pushrods. Best to actually measure needed length (which should really be done any time a cam is changed anyway).
Last edited by farmington; Nov 1, 2019 at 08:43 PM.
Thread Starter
Instructor
Joined: Jul 2017
Posts: 225
Likes: 18
From: San Antonio TX
The heads were cleaned up a bit too...not sure how much.
i tested 2 different pushrods on passenger side using this method and came up with 1.25 and 1.5 turns respectively. But couldnt do proper EO/IC cause steering rack, so I just took 2 rockers that looked like they had the least amount of pressure on the springs.
1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.
i tested 2 different pushrods on passenger side using this method and came up with 1.25 and 1.5 turns respectively. But couldnt do proper EO/IC cause steering rack, so I just took 2 rockers that looked like they had the least amount of pressure on the springs.
1. Using the EO/IC method, get the lifter to the base circle of the cam.
2. Using a known length pushrod (7.400" is a good start with stock rockers) run the rocker arm bolt down to zero lash. This is easily done with your fingers "wiggling" the rocker, the point at which the "slack" is just gone is zero lash.
3. Set your torque wrench to 22 lb./ft. Tighten the rocker to full torque and count the number of turns it takes to get there. 1 full turn wtih a stock 8mm X 1.25 bolt is ~.047" preload as measured at the pushrod/rocker interface.
4. I normally shoot for 1 1/4 to 1 3/4 turns with stock type lifters like Comp 850's, LS1, LS7 etc.
Melting Slicks
Joined: Jun 2006
Posts: 2,497
Likes: 261
From: Miami Florida
Need to pin point the source and working hard and throwing away money hurts and don’t fix it sounds to me it could be a leaking header, a 5.00 bucks stethoscope from Harbor Freight can help a lot also be on the lookout for a noisy fuel injector easily found with the stethoscope also check for a rocker contacting a valve cover just put your finger on it and if hitting you’ll know right away, pls let us know what it was for others to benefit good luck...
Thread Starter
Instructor
Joined: Jul 2017
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From: San Antonio TX
Measured the pushrods today. Pulled passenger side valve cover (no fuel rail tool to pull driver’s side) and used cylinder #2. Couldnt turn motor over by hand even with the ratcheting wrench as it was hitting fan shroud...grr. So had Dad bump engine (coils pulled and hit start/stop real quick) while I felt for pushrod movement. Took a while to be certain but both exhaust and intake came out to 10.75 turns for zero lash...so when I did the math (10.75 x .05) + 6.800 = 7.3375 and then preload for ls7 lifters should be .060 - .100 so my 7.400 should be okay.
Thread Starter
Instructor
Joined: Jul 2017
Posts: 225
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From: San Antonio TX
The sound is intermittent. If it happens, it is usually 5-10 mins into the drive and then it goes away after a few minutes (usually rev and move rpm around to try and “fix” noise)
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Thread Starter
Instructor
Joined: Jul 2017
Posts: 225
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From: San Antonio TX
the only thing I can think of due to it being intermittent, is the heads/block heat up faster and expand causing less preload until the chromoly pushrods warm up and then it is back in spec?
Either that or something is off alignment/ slightly bent and it only makes noise when it rotates into a certain position?
Will keep digging and keep y’all posted. I dont think it is doing much harm, just embarassing to be clacking like that and definitely not optimal
Melting Slicks
Joined: Oct 2015
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From: Mead Wash
2020 C6 of the Year Finalist - Modified
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Noise
Post your cam specs. Doesn’t sound like there is any lope to it. Also sounds tight except for a lifter or rocker arm.
Thread Starter
Instructor
Joined: Jul 2017
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From: San Antonio TX
