Another broken YT
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
Another broken YT
This is the second YT rocker that has broken on me. The first one was several years ago on this same engine. I took them at their word that there was a bad run that they had corrected. They were very responsive and sent me another set all the way from Australia and I had it 4 days later.
This morning, I was pulling the car out of the garage this morning. I got about 50 yards from the house and I heard a rattle and then a dead miss. I pulled the car over immediately. This afternoon when I got home I pulled the valve cover abd found this:
The first time, I had to pull the head to get all the pieces out. Luckily, I'm fortunate that the piece that broke of is one piece and was sitting next to the spring.
I'm running PAC 1521's with .643 lift cam 234 degree cam. The rocker geometry is properly setup.
I was willing to give them the benefit of the doubt the first time but not twice. This is a street car with the rev limiter set at 6800 and it never sees that.
Needless to say, YT's won't be going back in.
Just an FYI.
This morning, I was pulling the car out of the garage this morning. I got about 50 yards from the house and I heard a rattle and then a dead miss. I pulled the car over immediately. This afternoon when I got home I pulled the valve cover abd found this:
The first time, I had to pull the head to get all the pieces out. Luckily, I'm fortunate that the piece that broke of is one piece and was sitting next to the spring.
I'm running PAC 1521's with .643 lift cam 234 degree cam. The rocker geometry is properly setup.
I was willing to give them the benefit of the doubt the first time but not twice. This is a street car with the rev limiter set at 6800 and it never sees that.
Needless to say, YT's won't be going back in.
Just an FYI.
Tech Contributor
Joined: Jan 2007
Posts: 19,292
Likes: 1,109
From: Dyer, IN
This is the second YT rocker that has broken on me. The first one was several years ago on this same engine. I took them at their word that there was a bad run that they had corrected. They were very responsive and sent me another set all the way from Australia and I had it 4 days later.
This morning, I was pulling the car out of the garage this morning. I got about 50 yards from the house and I heard a rattle and then a dead miss. I pulled the car over immediately. This afternoon when I got home I pulled the valve cover abd found this:
The first time, I had to pull the head to get all the pieces out. Luckily, I'm fortunate that the piece that broke of is one piece and was sitting next to the spring.
I'm running PAC 1521's with .643 lift cam 234 degree cam. The rocker geometry is properly setup.
I was willing to give them the benefit of the doubt the first time but not twice. This is a street car with the rev limiter set at 6800 and it never sees that.
Needless to say, YT's won't be going back in.
Just an FYI.
This morning, I was pulling the car out of the garage this morning. I got about 50 yards from the house and I heard a rattle and then a dead miss. I pulled the car over immediately. This afternoon when I got home I pulled the valve cover abd found this:
The first time, I had to pull the head to get all the pieces out. Luckily, I'm fortunate that the piece that broke of is one piece and was sitting next to the spring.
I'm running PAC 1521's with .643 lift cam 234 degree cam. The rocker geometry is properly setup.
I was willing to give them the benefit of the doubt the first time but not twice. This is a street car with the rev limiter set at 6800 and it never sees that.
Needless to say, YT's won't be going back in.
Just an FYI.
http://forums.corvetteforum.com/c5-t...ht-rocker.html
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
Damn Kevin......two years ago .....right to the day!
http://forums.corvetteforum.com/c5-t...ht-rocker.html
http://forums.corvetteforum.com/c5-t...ht-rocker.html
Shawn Miller is talking with Crane about a new rocker they haven't even introduced yet. That's one possiblity or T&D is another. Jesel is just way overkill for the Cruiser.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
Not sure if you saw this elsewhere but I will post it for information, it is a post by Brian Tooley with some things to keep in mind. At one time I ran the old Crane LS1 rockers and their wipe pattern was very wide, likely because of the "quick lift" and required geometry to achieve this. Will be interested in what you find out from Crane as I am running YT's at this time too.
Quick question, do you know what your open force is on the valve springs?
Link to Brian Tooley's Post
Quick question, do you know what your open force is on the valve springs?
Link to Brian Tooley's Post
Melting Slicks
Joined: Jun 2005
Posts: 2,396
Likes: 52
From: Sicamous BC
Gad, this type of thing makes me nervous. I've LSK lobes, mid .650 lift, new springs are rated .675.......my new heads are soon to be shipped.
Please update what you decide to replace the Yella's with, I should maybe re think installing mine.
Please update what you decide to replace the Yella's with, I should maybe re think installing mine.
Pro
Joined: Oct 2000
Posts: 545
Likes: 1
From: Charlotte NC
This is the second YT rocker that has broken on me. The first one was several years ago on this same engine. I took them at their word that there was a bad run that they had corrected. They were very responsive and sent me another set all the way from Australia and I had it 4 days later.
This morning, I was pulling the car out of the garage this morning. I got about 50 yards from the house and I heard a rattle and then a dead miss. I pulled the car over immediately. This afternoon when I got home I pulled the valve cover abd found this:
The first time, I had to pull the head to get all the pieces out. Luckily, I'm fortunate that the piece that broke of is one piece and was sitting next to the spring.
I'm running PAC 1521's with .643 lift cam 234 degree cam. The rocker geometry is properly setup.
I was willing to give them the benefit of the doubt the first time but not twice. This is a street car with the rev limiter set at 6800 and it never sees that.
Needless to say, YT's won't be going back in.
Just an FYI.
This morning, I was pulling the car out of the garage this morning. I got about 50 yards from the house and I heard a rattle and then a dead miss. I pulled the car over immediately. This afternoon when I got home I pulled the valve cover abd found this:
The first time, I had to pull the head to get all the pieces out. Luckily, I'm fortunate that the piece that broke of is one piece and was sitting next to the spring.
I'm running PAC 1521's with .643 lift cam 234 degree cam. The rocker geometry is properly setup.
I was willing to give them the benefit of the doubt the first time but not twice. This is a street car with the rev limiter set at 6800 and it never sees that.
Needless to say, YT's won't be going back in.
Just an FYI.
I lost the needle bearings in a brand new set. Went to Jesels.
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
Not sure if you saw this elsewhere but I will post it for information, it is a post by Brian Tooley with some things to keep in mind. At one time I ran the old Crane LS1 rockers and their wipe pattern was very wide, likely because of the "quick lift" and required geometry to achieve this. Will be interested in what you find out from Crane as I am running YT's at this time too.
Quick question, do you know what your open force is on the valve springs?
Link to Brian Tooley's Post
Quick question, do you know what your open force is on the valve springs?
Link to Brian Tooley's Post
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Instructor
Joined: Jun 2006
Posts: 107
Likes: 0
From: Siloam Springs AR
Thank you for posting your experience. I noticed it was the offset intake arm that broke. Was it also the intake rocker that failed on you the first time?
You said you had pretty strong springs. Are you using the hollow stem intake valves? I would say you are probably near the top end of the scale on the demands you are placing on these rockers.
You said you had pretty strong springs. Are you using the hollow stem intake valves? I would say you are probably near the top end of the scale on the demands you are placing on these rockers.
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
Thank you for posting your experience. I noticed it was the offset intake arm that broke. Was it also the intake rocker that failed on you the first time?
You said you had pretty strong springs. Are you using the hollow stem intake valves? I would say you are probably near the top end of the scale on the demands you are placing on these rockers.
You said you had pretty strong springs. Are you using the hollow stem intake valves? I would say you are probably near the top end of the scale on the demands you are placing on these rockers.
It's not like it happened at 1300 feet turning 8k RPM. Actually, it should be pretty understressed. Bottom line - this shouldn't have happened once much less twice. Both on the intake rocker.
Melting Slicks
Joined: Jun 2005
Posts: 2,396
Likes: 52
From: Sicamous BC
I was just re reading & noticed the 1521 springs & the lift of your cam, the lift of my cam is very close to yours. The individual that is doing my new cylinder heads had a concern about my previous heads with the 1521 springs rated & set to .700 lift. As it was explained to me the spring rated lift & the cam should be withing .025 so in our case the spring should be rated @ .675 not .700. Chris explained why that is & it was really over my head, honestly I did not really give much thought as it was going to be corrected anyways.
That conversation just came back to me re reading your post, building cylinder heads is what this guy does & he is very well respected. If you are interested in quizzing him about this problem I can pass on his contact information.
That conversation just came back to me re reading your post, building cylinder heads is what this guy does & he is very well respected. If you are interested in quizzing him about this problem I can pass on his contact information.
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
I was just re reading & noticed the 1521 springs & the lift of your cam, the lift of my cam is very close to yours. The individual that is doing my new cylinder heads had a concern about my previous heads with the 1521 springs rated & set to .700 lift. As it was explained to me the spring rated lift & the cam should be withing .025 so in our case the spring should be rated @ .675 not .700. Chris explained why that is & it was really over my head, honestly I did not really give much thought as it was going to be corrected anyways.
That conversation just came back to me re reading your post, building cylinder heads is what this guy does & he is very well respected. If you are interested in quizzing him about this problem I can pass on his contact information.
That conversation just came back to me re reading your post, building cylinder heads is what this guy does & he is very well respected. If you are interested in quizzing him about this problem I can pass on his contact information.
Tech Contributor
Joined: Sep 2005
Posts: 1,731
Likes: 82
From: New Market AL
I think you are maxing out that LS3 rocker design with your cam profile. My personal experience with Y/T rockers on AFR cathedral port heads is over 100,000 miles now without any problems from the rocker arms. My first cam was 224/230 with XFI lobes and now 232/234 with X-ER. You are wise to try a different brand of rocker arm at this point.
Melting Slicks
Joined: Jun 2005
Posts: 2,396
Likes: 52
From: Sicamous BC
I did not want to leave this, when broken rockers are searched potentially there maybe other reasons. As well I will be installing my new cylinder heads with the YT rockers & do not want to suffer the same issue.
The situation is called Reverse Harmonics & it can occur when the maximum lift of the cam is to far away from coil bind of the spring. The 1521 springs are rated @ .700, from there it is another .060 before bind occurs. The cam lift as in my case is .650, so I'm .050 less than the spring rated maximum lift plus the additional .060, so really I'm .110 from coil bind. I will replace my PAC 1521 springs with some that are closer to the max lift of cam.
This I'm told this can cause broken Springs, Rockers & damaged valve tips.
I'm passing this information along, it maybe worth while following up.
The situation is called Reverse Harmonics & it can occur when the maximum lift of the cam is to far away from coil bind of the spring. The 1521 springs are rated @ .700, from there it is another .060 before bind occurs. The cam lift as in my case is .650, so I'm .050 less than the spring rated maximum lift plus the additional .060, so really I'm .110 from coil bind. I will replace my PAC 1521 springs with some that are closer to the max lift of cam.
This I'm told this can cause broken Springs, Rockers & damaged valve tips.
I'm passing this information along, it maybe worth while following up.
Last edited by CTD; Jul 3, 2012 at 08:41 PM.
Thread Starter
Race Director
Joined: Dec 2004
Posts: 13,760
Likes: 75
From: Haymarket VA
I did not want to leave this, when broken rockers are searched potentially there maybe other reasons. As well I will be installing my new cylinder heads with the YT rockers & do not want to suffer the same issue.
The situation is called Reverse Harmonics & it can occur when the maximum lift of the cam is to far away from coil bind of the spring. The 1521 springs are rated @ .700, from there it is another .060 before bind occurs. The cam lift as in my case is .650, so I'm .050 less than the spring rated maximum lift plus the additional .060, so really I'm .110 from coil bind.
This I'm told this can cause broken Springs, Rockers & damaged valve tips.
I'm passing this information along, it maybe worth while following up.
The situation is called Reverse Harmonics & it can occur when the maximum lift of the cam is to far away from coil bind of the spring. The 1521 springs are rated @ .700, from there it is another .060 before bind occurs. The cam lift as in my case is .650, so I'm .050 less than the spring rated maximum lift plus the additional .060, so really I'm .110 from coil bind.
This I'm told this can cause broken Springs, Rockers & damaged valve tips.
I'm passing this information along, it maybe worth while following up.
