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What all can cause excessive valve train noise (HR)?

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Glen Koenig

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Discussion starter · #1 ·
I'm working on friends Gen 2 LT1 that goes through various levels of valve train noise. It's not horrible at idle or at high rpm. But it gets noisy in a unsettling ways during:
  1. Tip in off idle momentary clatter
  2. Loud and obnoxious noise on moderate acceleration, like when leaving a stop sign.
  3. when the TCC locks up as the engine transitions from moderate rpm and low load to low rpm and moderate load.
I'm mostly curious to learn what are the factors that contribute to valve train noise, and how to mitigate them. I'm also tuning the ECU for the car and false knock is a problem.

Here are the details about the engine and valve train:
  • Iron block LT1 4.040" bore, 6" scat rod, stock crank, Mahle power pack pistons
  • Main bearing clearances (King XP's): 0.0015-0.0020 & 0.0027 rear
  • Rod bearing clearances (King XPN): 0.0025-0.0027
  • Runs 10w40 synthetic, when he remembers. Doh!
  • SCR: variable (11.2 - 11.7)
  • GM Aluminum heads ported with 2.00/1.56 valves
  • 10+ year old valve springs, I'm guessing that they're Patriot Gold's with CR retainers. Likely spec'd for a CC 503 cam
  • Erson HR cam (110995) 226/234, .585 lift with 1.60 ratio (Installed dead on!)
  • Spring Installed height: 0.765"
  • 2 year old GM LS1 lifters preloaded to .050", checked with a dial indicator (just past 3/4 turn)
  • CV7000 7.00" 3/8" pushrods
  • Vintage 2000's Comp Cams Pro Magnum Self Aligning RR's, 1.6:1. Checked them all, had to replace one due to a sticky trunnion.
I'm trying really hard to overthink this thing. I just don't want it to come apart on the guy. He already had one rocker come off, but it was well over year after I rebuilt it. My problem is that I don't know why it came off because the poly lock didn't back off. However, he was running 10w30 Mob1 from Walmart at the time.

Possible contributing factors?
  1. lifter preload
  2. pushrod length
  3. valve spring pressure
  4. valve spring installed height
  5. cheap/old rockers
  6. inadequate lifters
  7. bad rocker and pushrod combo
  8. oil weight, lack of oil up top
  9. Pushrod hitting the head
  10. wrong pushrod tip
  11. miscellaneous: radio turned off or volume too low, or restrictive exhaust, tell him to knock the mufflers off by hitting them with his purse
 
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#2 ·
Your description almost sounds more like detonation than valve train noise. The times when it is occurring is when there is prime detonation conditions. Have you actually heard it ? I have one customer who does LT-1 engines almost exclusively. I can ask him but need more details. Ignition system and curve ? Valve springs for sure ?
 
#3 ·
Glen have you considered header leak(s)?

Wouldn't be the first time.
 
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Discussion starter · #4 ·
BillK said:
Your description almost sounds more like detonation than valve train noise. The times when it is occurring is when there is prime detonation conditions. Have you actually heard it ? I have one customer who does LT-1 engines almost exclusively. I can ask him but need more details. Ignition system and curve ? Valve springs for sure ?
Click to expand...
Karl said to tell you that the engine is over 10 years old, and that he built it.
I did a rebuild of it less than two years ago when I installed a new cam for him.
I've listened to it using headphones through a Plex Knock Monitor, and it is definitely not detonating, other than at low rpm and high load when I was locking the converter too low while tuning the VE.
I can determine detonation from mechanical engine noise based on the sound through the headphones as well as the knock level. While these roller rockers are loud, the knock level rarely exceeds 30. However, the stock ECU calibration has such low knock sensor level settings (8-13) that the racket these lifters make is enough to trigger false knock.
On a side note, what about a roller rocker makes them noisier than stamped rockers?
 
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#6 ·
I dont know why roller rockers are noisy but it always seems that they are :) I wonder if it is the fact that there is bearings and the roller tip that always have a little clearance. Also it seems that aluminum valve covers always seem noisier and most guys running roller rockers also have aluminum valve covers ??

What does it do in neutral if you hit the throttle ? How about if you slowly run it up through the rpms in neutral ? Has it done it since the rebuild or a recent problem ?

The way you are describing the times that it does it makes detonation the normal thought but also a header leak like Levon said. Can you take an audio recording of the noise ? Did Karl have any thoughts on it ?
 
Discussion starter · #7 ·
You know, I don't recall if it was this noisy before the new cam. I do know it has been noisy since the cam swap. Could there be a slight difference in base circle of the cam? I'm pretty sure I would have re-measured PR length, but I did re-use the ones that Karl installed 10+ years ago.
Karl did suggest to try a longer pushrod just to see if it helps.

I'll also say that these GM LS1 lifters seem to bleed down faster than I expected. If I set pre-load after the car was off for a day or more I could turn the nut by hand on almost all of them. But if I adjusted them again the same day they were still pumped up nicely. I also tried more pre-load, but it didn't seem to help that much. They're back at 0.050" now, and the car runs great.
 
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#8 ·
Pull the valve covers and look for any shinny spots/rubbing marks on the inside of the covers where the roller rockers might be hitting. If shinny spots are visible, you can try to install a thicker valve cover gaskets... or if these are aluminum valve covers, you can slightly clearance the inside of the valve covers (or the roller rockers) where the rubbing is accruing.
 
#9 ·
Glen Koenig said:
I'm working on friends Gen 2 LT1 that goes through various levels of valve train noise. It's not horrible at idle or at high rpm. But it gets noisy in a unsettling ways during:
  1. Tip in off idle momentary clatter
  2. Loud and obnoxious noise on moderate acceleration, like when leaving a stop sign.
  3. when the TCC locks up as the engine transitions from moderate rpm and low load to low rpm and moderate load.
I'm mostly curious to learn what are the factors that contribute to valve train noise, and how to mitigate them. I'm also tuning the ECU for the car and false knock is a problem.

Here are the details about the engine and valve train:
  • Iron block LT1 4.040" bore, 6" scat rod, stock crank, Mahle power pack pistons
  • Main bearing clearances (King XP's): 0.0015-0.0020 & 0.0027 rear
  • Rod bearing clearances (King XPN): 0.0025-0.0027
  • Runs 10w40 synthetic, when he remembers. Doh!
  • SCR: variable (11.2 - 11.7)
  • GM Aluminum heads ported with 2.00/1.56 valves
  • 10+ year old valve springs, I'm guessing that they're Patriot Gold's with CR retainers. Likely spec'd for a CC 503 cam
  • Erson HR cam (110995) 226/234, .585 lift with 1.60 ratio (Installed dead on!)
  • Spring Installed height: 0.765"
  • 2 year old GM LS1 lifters preloaded to .050", checked with a dial indicator (just past 3/4 turn)
  • CV7000 7.00" 3/8" pushrods
  • Vintage 2000's Comp Cams Pro Magnum Self Aligning RR's, 1.6:1. Checked them all, had to replace one due to a sticky trunnion.
I'm trying really hard to overthink this thing. I just don't want it to come apart on the guy. He already had one rocker come off, but it was well over year after I rebuilt it. My problem is that I don't know why it came off because the poly lock didn't back off. However, he was running 10w30 Mob1 from Walmart at the time.

Possible contributing factors?
  1. lifter preload
  2. pushrod length
  3. valve spring pressure
  4. valve spring installed height
  5. cheap/old rockers
  6. inadequate lifters
  7. bad rocker and pushrod combo
  8. oil weight, lack of oil up top
  9. Pushrod hitting the head
  10. wrong pushrod tip
  11. miscellaneous: radio turned off or volume too low, or restrictive exhaust, tell him to knock the mufflers off by hitting them with his purse
Click to expand...
Part of the problem could be due to a possible asymmetrical lobe on the cam itself. Back in the late 70's when Comp came out with the original 268H it was a fantastic cam but they did have lifter noise and that was with a flat tappet cam, could be the same with the Erson cam you have. Scooter Brothers at comp told me the lifter noise on the 268H was due to the cam lobe profile, namely the closing side of the intake ramp. Some say Hyd rollers need more oil pressure, but these days who knows with hyd roller lifters as it seem to be a crap shoot with them.
 
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Discussion starter · #10 ·
RifRaf, not hitting the VC's.

68, I forgot to add that, but I was also wondering if the ramp rate on the lobes was a contributing factor.
I'll call Erson tomorrow to see what springs and pressures they recommend for that cam.
 
#11 ·
It wasn't just the 268. I had a 280 that drove me crazy.
 
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#12 ·
Any idea what the seat and open pressures are? I know my 454 HO had a faint tick under certain scenarios that drove me nuts. And this was a factory sealed engine. When I increased spring pressure, it made more noise.

can you take a shim out or maybe try +50 locks to see if you get a change?
 
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#13 ·
Glen,
I still think you are going in the wrong direction BUT I cant hear the noise so I could be wrong. I simply don't believe the lifters would only make noise under the three conditions you mentioned but not in between. If it was the cam grind then why would it not do it at other rpms / conditions ? Same with the lifters.

E110995 is a custom grind but most of their cams in that range call for their 3200 or 3400 spring.
The 3200 is a single spring 135 @ 1.750 360 @ 1.200 The 3400 is a dual spring 140 @ 1.800 330 @ 1.200
 
Discussion starter · #14 ·
BillK said:
Glen,
I still think you are going in the wrong direction BUT I cant hear the noise so I could be wrong.
Click to expand...
Meaning it's got to be detonation? Or some other noise and not the lifters?
I'm kicking myself for not getting an actual recording of the sound through the headphones. But I can 100% guarantee that there are no exhaust leaks, the bottom end is nice and tight, it has an electric water pump and the excess noise has the exact same rhythm as the valvetrain.
At least that's what it sounds like through the Plex, which is basically an electronic stethoscope with filtering and harmonic settings to help you zero in on the sound of detonation. The rockers sound like lead footed ants marching along with the rpm's and the detonation sounds like a sharp ping, like a mini ballpeen hammer hitting an anvil.
 
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#15 ·
Glen Koenig said:
Meaning it's got to be detonation? Or some other noise and not the lifters?
Click to expand...
Thats what I am thinking. And to be honest with you the sound through the headphones means nothing to me :( But I can definitely tell what detonation "sounds" like with my human ear.

Also, I bet I have had ten guys over the years "guarantee" that they didn't have an exhaust leak but darned if thats not what it turned out to be :) The car is an automatic so you should be able to power brake it and hear it sitting still.
 
Discussion starter · #16 ·
BillK said:
...Also, I bet I have had ten guys over the years "guarantee" that they didn't have an exhaust leak but darned if thats not what it turned out to be :)
Click to expand...
Sure, but did any of them say that they'd kiss your @SS in the county square, and give you an hour to draw a crowd?

Turn it up...
 
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#17 ·
Is a Gen 2 LT1 like an LS? if it is, with such a small cam, why the roller rockers? If it is an LS valvetrain, the stock stuff should be fine.
 
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Discussion starter · #18 · (Edited)
69-CHVL said:
Any idea what the seat and open pressures are? I know my 454 HO had a faint tick under certain scenarios that drove me nuts. And this was a factory sealed engine. When I increased spring pressure, it made more noise.

can you take a shim out or maybe try +50 locks to see if you get a change?
Click to expand...
No, sadly. My spring tester is old junk.
Erson said to use their 3400 springs. Will get them and see what happens.
 
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#19 ·
Geo71 said:
Is a Gen 2 LT1 like an LS? if it is, with such a small cam, why the roller rockers? If it is an LS valvetrain, the stock stuff should be fine.
Click to expand...
No, It is more like a traditional Small Block. Reverse cooling and some other changes but definitely not like an LS.
 
#20 ·
LevonH said:
It wasn't just the 268. I had a 280 that drove me crazy.
Click to expand...
Funny thing is, the newer 268 and 280H cams are different with different lobes. If one wants the old grind you have to have Comp grind it for you. I ran the best of 12.26 with that old 268H, not too shabby for a puppy cam.
 
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