question re: valve train noises that dont seem normal.
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
question re: valve train noises that dont seem normal. the car has double springs/titanium retainers and stock rockers. Cam is a cheatr cam. Basically the sewing machine at idle i can deal with. But during accel most noticably between 2k to 3300 or so it is quite loud. It quiets up after that and before that. I have 5.3L heads, .040" head gaskets and 7.40" pushrods. I tightened every rocker to 22 ft/lbs like i've always done before and never had a problem. This is my first combo that isnt stock though so that probably doesnt matter much. I noticed its most pronounced on accel and decel between the above rpms. Its still there at a steady rpms but it will get louder if i accel through that rpm band or if im in that band and accel it will get a tad louder (between 2k-3300). Can anyone give me some advice?
Car runs great though with no drivability issues or Ltrim issues.
Thanks
Dave
Car runs great though with no drivability issues or Ltrim issues.
Thanks
Dave
Thread Starter
Joined: May 2004
Posts: 1,080
Likes: 0
From: Elgin, Illinois
i didnt check for clearance. Ill yank a rocker and see. I didnt even think to look for that. I looseed the passenger rockers and retorqued all to 22 ft/lbs. Im wondering if the preload is the issue here. I have a 5.3L heat w/ a 63cc chamber, .040" gaskets and the 7.40" pushrod. This is the pushrod brent@tea recommended. I did hear from a few others that 7.35" might be a better length. I should have measured. I've never taken anyones word for this since deck heights, head heights, etc vary.
Dave
Dave
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
a quick vid. Sorry about the compression this is my first vid ive made for the computer.
http://tech.cfbinc.com/dave/valvetrain.avi
Dave
http://tech.cfbinc.com/dave/valvetrain.avi
Dave
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
I was thinking a while back and doing some calcs. Basically if the cheatr cam has a .030" reduced base circle and if in fact 5.3L heads have a 63cc chamber unmilled, coupled w/ my .040" cometics, id need a pushrod of 7.443 or 7.45". I got this calc like this: Graphite gasket " .053 vs .040 (-.013") and base circle difference of -.030" Of course the valve seat and stem height will affect this but in my prelim calcs, the pushrod may be too short if these heads are infact unmilled. Now my question is, is a 5.3L head rocker pedistal the same height as a 5.7L pedistal height? This would explain my loud valvetrain during acceleration..
Dave
Dave
TECH Senior Member
Joined: Mar 2004
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From: BFE
Also with HS there has been some head and valve cover clearance issues on some motors. Check that too.
Your p-rod choice is good unless you base circle is over .055 difference VS stock (can't you get that figure from TR?)
Your p-rod choice is good unless you base circle is over .055 difference VS stock (can't you get that figure from TR?)
Wow, my car doesn't sound like that. That's REALLY loud valve noise. Something is mismatched. Did you change the oil pump too when you swapped cams. Sometimes the o-ring gets a tear and will restrict oil to your lifters, making a loud clattering like that.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
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Verdad Gallardo TECH Senior Member
Joined: Mar 2004
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Likes: 17
From: BFE
Originally Posted by TT_Vert
with HS? harland sharp? I have OEM rockers.
Dvae
Dvae
But with dual springs retainers some can have clearance issues with underside of stock rockers.
Launching!
Joined: Apr 2005
Posts: 205
Likes: 1
From: Atlanta area, GA
Well, if it's any consolation, LPE's techs will swear up and down (and sideways) that they re-use the stock pushrods on GT2-3 cam swaps all day long. We already know the FACTS.. The FACTS are that the LS6 cam has a smaller base circle than the LS1 cam, and the LPE cam has a smaller base circle than the LS6 cam. We also know GM engineers accounted for the smaller base circle of the LS6 cam w/ longer valves.
So it's clear that even well known and respected tuners are more than willing to "let it ride" when it comes to the small technical details like choosing the correct push rod length for a given combination. The assumption (I guess) is that it will last long enough to not blow up in the first 30K miles or so.. By the time something bad happens you are convinced that "it's all part of the modding game, you take your chances, blah blah blah", and you'll probably head right back to the same tuner that was really responsible for the failure in the first place, so they can fix you up with a new and improved package.
So it's clear that even well known and respected tuners are more than willing to "let it ride" when it comes to the small technical details like choosing the correct push rod length for a given combination. The assumption (I guess) is that it will last long enough to not blow up in the first 30K miles or so.. By the time something bad happens you are convinced that "it's all part of the modding game, you take your chances, blah blah blah", and you'll probably head right back to the same tuner that was really responsible for the failure in the first place, so they can fix you up with a new and improved package.
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
im gonna check the retainer to rocker clearance in a bit and check preload w/ my dial indicator. I hope one if out of wack because if not, im out of ideas. I dont think anyone would deal w/ the noise im hearing so im hoping its something simple..
Thanks guys!!
Dave
Thanks guys!!
Dave
TT_Vert,
I'm very interested in what you find out. I had the same noise, now after replacing heads, pushrods, shortblock (by a tuner), and rockers. I still have the noise. I've just replaced the lifters (again, Comp 850-16's) and I'm waiting on some new headers before I can see if the new lifters help. I had the stock rockers, now I have the HS's (.065 preload). There's not much left to try out!
Byter
I'm very interested in what you find out. I had the same noise, now after replacing heads, pushrods, shortblock (by a tuner), and rockers. I still have the noise. I've just replaced the lifters (again, Comp 850-16's) and I'm waiting on some new headers before I can see if the new lifters help. I had the stock rockers, now I have the HS's (.065 preload). There's not much left to try out!
Byter
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
i went ahead and checked preload w/ a dial. This is odd but this is what im coming up with.. I set the rocker to zero lash and tightened to 22 ft/lbs (took about 1.5 turns) and i get about .080" but it creeps back down to .020" in a matter of 10 seconds. I then rezero'd the DA at 22ft/lbs and loosened. I saw about .120". I think that could be because im loosening the rocker past zero lash when im loosening. Why would the clearance creep back down like that??
EDIT::
N/M i was reading that backwards. What is happening is the plunger is creeping down slowly and the dial is actually showing .080" after a few seconds. Is this normal?
Thanks
Dave
EDIT::
N/M i was reading that backwards. What is happening is the plunger is creeping down slowly and the dial is actually showing .080" after a few seconds. Is this normal?
Thanks
Dave
Last edited by TT_Vert; Jul 5, 2005 at 04:35 PM.
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
btw is it normal for the plunger to slowly depress? if so,what reading is preload? The reading before plunger starts to depress or after its done depressing at 22 ft/lbs?
Dave
Dave
Originally Posted by TT_Vert
btw is it normal for the plunger to slowly depress? if so,what reading is preload? The reading before plunger starts to depress or after its done depressing at 22 ft/lbs?
Dave
Dave
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
ok well i still have the noise> I parked the car next to another car and revved it and the noise is there from 1500 up to 6k or so rpms. There is no way this is normal.. I took a jack handle and listened while a friend revved it and it seems the sound is coming from near the exhaust or by the valves themselves. Sounds almost like rod knock
Dave
Dave
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
do OEM lifter lube holes have to go a certain way? i know they can only go 2 ways but i seemed to recall they all didnt go one way. They were just thrown in . I could be wrong and this could be my valvetrain noise. You heads/cam guys.. did you notice when you did your h/c install?
Thanks
dave
Thanks
dave
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
thanks brent, i posted this right before i asked you. im just getting paaranoid at this point. Another thing i was reading is a guy had a very similar sound and combo and put in 7.350" pushrods it cured his problem. I do have quite a bit of preload, so i may go pickup some 7.350"ers and see what happens.
Dave
Dave