Valvetrain Noise & New Cam
03-30-2005, 05:09 PM
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Valvetrain Noise & New Cam Just finished installing an '03 ZO6 Cam and PP LS6 heads on a '99 LS1. Car fired right up. Sounds good, idles well, no engine shake or hint of a missfire. Seems to be alot of valvetrain noise, how long does it take the lifters to "pump" back up? I only ran it for about 20 seconds, it's been a while since I have doen a cam swap, can't really remember how much initial start up noise is normal.
Thanks,
Joe
Thanks,
Joe
03-30-2005, 05:41 PM
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Originally Posted by SilverM6SS
Just finished installing an '03 ZO6 Cam and PP LS6 heads on a '99 LS1. Car fired right up. Sounds good, idles well, no engine shake or hint of a missfire. Seems to be alot of valvetrain noise, how long does it take the lifters to "pump" back up? I only ran it for about 20 seconds, it's been a while since I have doen a cam swap, can't really remember how much initial start up noise is normal.
Thanks,
Joe
Thanks,
Joe
03-30-2005, 06:22 PM
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Originally Posted by Flareside
Mine made noise for at least 5 minutes, then every once in a while for probably another 10 minutes after that. Just let it idle.
03-30-2005, 09:50 PM
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Originally Posted by SilverM6SS
Stock pushrods. Are patriot double springs too much for stock pushrods?
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03-30-2005, 10:05 PM
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It's also possible that the stock pushrods may not be long enough. The LS6 cam base circle is .030" smaller than the LS1 cam. That would put the lifters down the hole .015" more than the stock LS1 cam would. The stock pushrods are 7.380" long. It probably will clear up but if it doesn't it's possible you don't have enough preload and switching to a 7.400" long pushrod. Also a hardened pushrod may help your valvetrain stability at high rpm's with the extra load the new springs puts on them. This is of course if the Patriot rocker geometry is the same as the stock LS1 heads.
What you could do is check the preload and the geometry to make sure the pushrods are running where they need to be... IF the valvetrain doesn't quiet down.
What you could do is check the preload and the geometry to make sure the pushrods are running where they need to be... IF the valvetrain doesn't quiet down.
03-30-2005, 10:29 PM
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Originally Posted by ArKay99
It's also possible that the stock pushrods may not be long enough. The LS6 cam base circle is .030" smaller than the LS1 cam. That would put the lifters down the hole .015" more than the stock LS1 cam would. The stock pushrods are 7.380" long. It probably will clear up but if it doesn't it's possible you don't have enough preload and switching to a 7.400" long pushrod. Also a hardened pushrod may help your valvetrain stability at high rpm's with the extra load the new springs puts on them. This is of course if the Patriot rocker geometry is the same as the stock LS1 heads.
What you could do is check the preload and the geometry to make sure the pushrods are running where they need to be... IF the valvetrain doesn't quiet down.
What you could do is check the preload and the geometry to make sure the pushrods are running where they need to be... IF the valvetrain doesn't quiet down.
Thanks
03-30-2005, 11:38 PM
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Originally Posted by ArKay99
It's also possible that the stock pushrods may not be long enough. The LS6 cam base circle is .030" smaller than the LS1 cam. That would put the lifters down the hole .015" more than the stock LS1 cam would. The stock pushrods are 7.380" long. It probably will clear up but if it doesn't it's possible you don't have enough preload and switching to a 7.400" long pushrod. Also a hardened pushrod may help your valvetrain stability at high rpm's with the extra load the new springs puts on them. This is of course if the Patriot rocker geometry is the same as the stock LS1 heads.
What you could do is check the preload and the geometry to make sure the pushrods are running where they need to be... IF the valvetrain doesn't quiet down.
What you could do is check the preload and the geometry to make sure the pushrods are running where they need to be... IF the valvetrain doesn't quiet down.
03-31-2005, 03:17 PM
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Originally Posted by zo6vetteman2003
That is correct info. about the base circle. You should always replace the pushrods whenever going to a more aggressive cam in his case especially with those springs. The stock are too light and have too much flex. and tend to break in hp applications. Chromemoly rods are cheap insurance and a one time expense to help you sleep better at night.
I thought stock pushrod length was 7.4"?????
03-31-2005, 06:33 PM
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Originally Posted by SilverM6SS
I thought stock pushrod length was 7.4"?????
I debated between the LS6 cam and the LPE GT2-3 that I finally decided on, and I had both cams here along with the stock LS1. The LS6 measured .029" smaller than the LS1 on the base circle.
I ran my stock pushrods for a while with the stock pushrods and the dual springs that cam on the AFR heads, and they worked fine right up to redline. They work fine with stock LS6 springs, and those have just as much open pressure as the AFR springs. No issues. Recently, I decided to install Comp beehive springs and longer pushrods (comp 7.425") because the stock pushrods were only yielding around .030" of lifter preload. With the stock cam, I was getting at least .060", so I knew the geometry had to be off now. The longer rods put everything back in position and quieted the valvetrain a bit more.
FYI, it's impossible to accurately recreate valvetrain geometry without taking the eventual lifter preload into account. If you use soft "checker" springs, you won't get any preload, and if you use normal valve springs and an empty lifter, the lifter plunger will sink as soon as you start lifting the valve off the seat, and it will really sink as pressure builds when the cam goes over the nose. IMO, the safest thing is to take good measurements and get the preload back to where it should be.
03-31-2005, 10:12 PM
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Originally Posted by Flareside
I can tell you that every reference I have, including the stock pushrods that I took out of my 03 LS1, are 7.400". I mic'd them myself just to be sure.
I debated between the LS6 cam and the LPE GT2-3 that I finally decided on, and I had both cams here along with the stock LS1. The LS6 measured .029" smaller than the LS1 on the base circle.
I ran my stock pushrods for a while with the stock pushrods and the dual springs that cam on the AFR heads, and they worked fine right up to redline. They work fine with stock LS6 springs, and those have just as much open pressure as the AFR springs. No issues. Recently, I decided to install Comp beehive springs and longer pushrods (comp 7.425") because the stock pushrods were only yielding around .030" of lifter preload. With the stock cam, I was getting at least .060", so I knew the geometry had to be off now. The longer rods put everything back in position and quieted the valvetrain a bit more.
FYI, it's impossible to accurately recreate valvetrain geometry without taking the eventual lifter preload into account. If you use soft "checker" springs, you won't get any preload, and if you use normal valve springs and an empty lifter, the lifter plunger will sink as soon as you start lifting the valve off the seat, and it will really sink as pressure builds when the cam goes over the nose. IMO, the safest thing is to take good measurements and get the preload back to where it should be.
I debated between the LS6 cam and the LPE GT2-3 that I finally decided on, and I had both cams here along with the stock LS1. The LS6 measured .029" smaller than the LS1 on the base circle.
I ran my stock pushrods for a while with the stock pushrods and the dual springs that cam on the AFR heads, and they worked fine right up to redline. They work fine with stock LS6 springs, and those have just as much open pressure as the AFR springs. No issues. Recently, I decided to install Comp beehive springs and longer pushrods (comp 7.425") because the stock pushrods were only yielding around .030" of lifter preload. With the stock cam, I was getting at least .060", so I knew the geometry had to be off now. The longer rods put everything back in position and quieted the valvetrain a bit more.
FYI, it's impossible to accurately recreate valvetrain geometry without taking the eventual lifter preload into account. If you use soft "checker" springs, you won't get any preload, and if you use normal valve springs and an empty lifter, the lifter plunger will sink as soon as you start lifting the valve off the seat, and it will really sink as pressure builds when the cam goes over the nose. IMO, the safest thing is to take good measurements and get the preload back to where it should be.
03-31-2005, 10:50 PM
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What I said correct to was the 2002, 2003, 2004 LS6 cam has a smaller base circle. This was done to correct valvetrain geometry in the LS6 because it has .6mm longer hollow stem valves and it was done to control valve motion with a .025" increased valvelift. The stock pushrods are 7.4" and a longer pushrod is needed to compensate for the smaller base circle of the 02 and later ZO6 cam. Ok, I went back and saw what you guys were looking at. NP. A longer set of pushrods are needed to make up the difference. Lobe base circle radius on a stock LS1 is .776in. or 19.7mm The stock LS6 cam has a lobe base circle radius of .748in. or 19.0mm. 028" or .7mm difference to be exact according to the omnipotent Will Handzel, Author and GM Performance Parts Program Manager. So the delemma is that most companies offer pushrods in .025" increments lol, so a 7.425" rod is needed to compensate for the smaller lobe base circle radius. The actual most common smaller pushrod size is 7.325" anyway. This is used with the LS6 cam and heads that have been milled.
Last edited by zo6vetteman2003; 03-31-2005 at 11:32 PM.
04-01-2005, 02:40 PM
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Originally Posted by zo6vetteman2003
What I said correct to was the 2002, 2003, 2004 LS6 cam has a smaller base circle. This was done to correct valvetrain geometry in the LS6 because it has .6mm longer hollow stem valves and it was done to control valve motion with a .025" increased valvelift. The stock pushrods are 7.4" and a longer pushrod is needed to compensate for the smaller base circle of the 02 and later ZO6 cam. Ok, I went back and saw what you guys were looking at. NP. A longer set of pushrods are needed to make up the difference. Lobe base circle radius on a stock LS1 is .776in. or 19.7mm The stock LS6 cam has a lobe base circle radius of .748in. or 19.0mm. 028" or .7mm difference to be exact according to the omnipotent Will Handzel, Author and GM Performance Parts Program Manager. So the delemma is that most companies offer pushrods in .025" increments lol, so a 7.425" rod is needed to compensate for the smaller lobe base circle radius. The actual most common smaller pushrod size is 7.325" anyway. This is used with the LS6 cam and heads that have been milled.
