Old Valvetrain (YT Rockers) vs new PAC valvetrain dyno (w/stock rockers)
03-20-2009, 09:10 AM
#21
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I've heard what is more important than the overall weight of the rocker is the weight located above the pushrod and spring. Don't know how you would measure that though, maybe Jonathon would know.
Kind of like 50 extra pounds in the roof of a car is a lot worse than 50 extra pounds in the floor board of a car. Center of gravity kind of thing.
My builder wasn't too impressed with my yella terra rockers. He said the roller tip moved around too much making it succeptable to binding.
Kind of like 50 extra pounds in the roof of a car is a lot worse than 50 extra pounds in the floor board of a car. Center of gravity kind of thing.
My builder wasn't too impressed with my yella terra rockers. He said the roller tip moved around too much making it succeptable to binding.
03-20-2009, 09:14 AM
#22
Interesting results. Chosing the proper springs can not be over stated, you dont need the baddest spring you can find on the market for every cam out there.
The PAC 1518 offers superior control(and light weight). Here is a great read.
http://www.racingsprings.com/beehivesprings.asp
The PAC 1518 offers superior control(and light weight). Here is a great read.
http://www.racingsprings.com/beehivesprings.asp
03-20-2009, 09:20 AM
#23
Gotcha. Honestly, I don't think there was one thing that fixed your problem. You reduced some SERIOUS weight in the valvetrain. I had a set of YT rockers and they were noticeably heavier than the stockers. Between going to a much lighter rocker and a SINGLE vs DUAL spring you lost a ****-ton of mass over the valve. I'd be interested in seeing if you just switched rockers if it cured your problem or just switched springs. Both were pretty significant changes.
03-20-2009, 11:48 AM
#24
Well said, Phil.
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03-20-2009, 01:44 PM
#26
Nice results. I personally don't recommend a YT rocker on anything other than an aftermarket casting that requires them. I've always had better luck with stock rockers on any GM casting.
I'm also like getting away with using a single spring whenever possible. Of course doubles are absolutely necessary for anything over .615 lift IMO.
I'm also like getting away with using a single spring whenever possible. Of course doubles are absolutely necessary for anything over .615 lift IMO.
03-20-2009, 02:26 PM
#27
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Some people had issues with the stock rockers puking needle bearings. Theyw would fall into the cylinder or bend the valves or a myriad of other horrible things. The failures were not many, but I've got enough invested in my engine that I considered the after market rockers to be 'insurance' by preventing that from happening.
I have read that the stock rockers are the lightest compared to any aftermarket offering.
I have read that the stock rockers are the lightest compared to any aftermarket offering.
03-20-2009, 02:28 PM
#28
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Some people had issues with the stock rockers puking needle bearings. Theyw would fall into the cylinder or bend the valves or a myriad of other horrible things. The failures were not many, but I've got enough invested in my engine that I considered the after market rockers to be 'insurance' by preventing that from happening.
I have read that the stock rockers are the lightest compared to any aftermarket offering.
I have read that the stock rockers are the lightest compared to any aftermarket offering.
03-20-2009, 02:40 PM
#29
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My issue with Harlan was the cost. If I remember correctly, it cost about the same to have Harlan upgrade the stockers as it cost to just have all new aftermarket pieces.
If I'm going to spend the money, then I want all new stuff!
Seriously, sending them to Harlan is probably one of the better ways to go but I couldn't bring myself to do it.
If I'm going to spend the money, then I want all new stuff!
Seriously, sending them to Harlan is probably one of the better ways to go but I couldn't bring myself to do it.
03-20-2009, 03:33 PM
#30
My issue with Harlan was the cost. If I remember correctly, it cost about the same to have Harlan upgrade the stockers as it cost to just have all new aftermarket pieces.
If I'm going to spend the money, then I want all new stuff!
Seriously, sending them to Harlan is probably one of the better ways to go but I couldn't bring myself to do it.
If I'm going to spend the money, then I want all new stuff!
Seriously, sending them to Harlan is probably one of the better ways to go but I couldn't bring myself to do it.
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Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
03-20-2009, 04:44 PM
#32
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I have read more than one story of valvetrain issues upstairs running aftermarket rockers and the sole cure being reinstallation of the stock rocker arms.
03-21-2009, 08:35 AM
#35
My issue with Harlan was the cost. If I remember correctly, it cost about the same to have Harlan upgrade the stockers as it cost to just have all new aftermarket pieces.
If I'm going to spend the money, then I want all new stuff!
Seriously, sending them to Harlan is probably one of the better ways to go but I couldn't bring myself to do it.
If I'm going to spend the money, then I want all new stuff!
Seriously, sending them to Harlan is probably one of the better ways to go but I couldn't bring myself to do it.
03-21-2009, 08:27 PM
#36
FormerVendor
I haven't seen these weird problems like that and I use YT all the time. Hmmmmmmmmm. Two guys on here spin over 7000 with them and run lower nines? These are the newer YT ultra lites though non-adjustable and aren't that heavy.
The stock rockers are great too though unless you run over a certain lift and can't fix the geometry problems. I don't use them on deals much over .600 lift very much and I don't shim the stands really but rather just get the right pushrods usually from Manton.
Of course that takes longer and a lot of people just don't want to wait.
The stock rockers are great too though unless you run over a certain lift and can't fix the geometry problems. I don't use them on deals much over .600 lift very much and I don't shim the stands really but rather just get the right pushrods usually from Manton.
Of course that takes longer and a lot of people just don't want to wait.
03-21-2009, 08:31 PM
#37
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https://ls1tech.com/forums/generatio...cs-inside.html
03-21-2009, 08:58 PM
#39
I haven't seen these weird problems like that and I use YT all the time. Hmmmmmmmmm. Two guys on here spin over 7000 with them and run lower nines? These are the newer YT ultra lites though non-adjustable and aren't that heavy.
The stock rockers are great too though unless you run over a certain lift and can't fix the geometry problems. I don't use them on deals much over .600 lift very much and I don't shim the stands really but rather just get the right pushrods usually from Manton.
Of course that takes longer and a lot of people just don't want to wait.
The stock rockers are great too though unless you run over a certain lift and can't fix the geometry problems. I don't use them on deals much over .600 lift very much and I don't shim the stands really but rather just get the right pushrods usually from Manton.
Of course that takes longer and a lot of people just don't want to wait.
03-22-2009, 10:41 AM
#40
FWIW, The ONLY thing I've seen make a car fall off a cliff like that on a dyno is/are VALVE SPRINGS! Improper length pushrods may make noise, or have some sort of issue, but they don't cause a complete lack of valve train control at a certain RPM.
BTW, the dip at 4000 will still be there even if you straighten the A/F out there.