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Diagnose broken rocker
Hey all,
I was letting my car idle in my drive way when I heard a click sound. I decided to pull the valve cover and a rocker arm fell out. Now, I am running a low lash camshaft with lash set to .008 which is within spec of the cam card. I have verified this several times and the card is correct. Now, my only thoughts is that since it is cold here in FL (temp 67 degrees) tha the lash was too tight. I am running aluminum heads with iron block. What are your thoughts http://www.clubcobra.com/photopost/d...66_Medium_.JPG http://www.clubcobra.com/photopost/d...64_Medium_.JPG http://www.clubcobra.com/photopost/d...65_Medium_.JPG http://www.clubcobra.com/photopost/d...63_Medium_.JPG http://www.clubcobra.com/photopost/d...62_Medium_.JPG |
Is that a DOVE roller rocker setup?
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Priobe ... those look Dove rockers ??? I had the same problem on my 427 Galaxie and found that the lip on the cup of the pushrod was contacting the rocker itself and on several , also the edge of the cup at full lift ( look for a shiny spot on the bottom of the rocker ) . In my case , it was caused by not having enough of the adjuster sticking out of the rocker ..... shortened up the pushrods and solved the problem . In looking at the photos , looks like you have about the same amount of thread on the adjuster sticking out above the nut as I did . Check all the pushrod cup lips also for signs of any contact with the adjuster . I also had a pushrod cup break off part of the cup .
Also possible you had a defective rocker , but I`m leaning towards contact somewhere . Bob |
I tnhe second picture, I see two things. Could just be the picture, though.
First, there's a crack around the adjuster. That crack may have led to the failure. Second (and this could just be the picture), there appears to be a small wear mark where the spring came in contact with the roker. |
lineslinger,
Yes those are Dove. Bobcat, I am not doubting that the adjustment maybe to small but I do not see any markings on the rocker (see 2nd photo) 3rd phot phot shows lift. I will double check. These are Smith brothers push rods. When speaking to Dove they almost sounded like they did not prefer the smith brothers push roids. Should I be using differnt push rods? Also, how can I verify that I have the correct length push rods. |
I think you may have the standard width rocker. I run their HD versions, alittle wider body, for greater strength. Unfortunately, I've broken one as well, driving home one evening about 2400 rpms. I also had a ford power parts rocker, with a bronze sleeve inside of an aluminum body, and broke one of those as well, on a track at about 4000 rpms. I'm thinking about getting a stainless steel set-up.
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These rockers were heading in same direction, in this case relief around adjuster screw/pushrod clearance had not been fully machined & cup of pushrod was milling its own clearance requirements.
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I used those type of rockers in my car and never had a problem. It may be because the engine builder cut the push rods to fit the rockers and made sure everything was perfect before he did the dyno tests. That was in 1997 and the engine is still as good as it was then and I did run it hard on the track and around the mountains before I had to sell it.
Ron |
Anthony,
These are the HD version, my pockets is still feeling it. As I looked closer at the rocker there is a c shaped indention in the rocker. How can I measure the distance that is needed to check if I need to replace all the push rods. Also, if I need to change the push rods what brand should I go with? The push rods are smith brothers. Or can I machine down the cup to allow clearance? |
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I feel your pain. |
With the valve lift and spring pressure you will not get aluminum to live with a shaft that big thru it---the failure has occurred to an alum part that has had a huge static load on it over an extended period of time
I have seen numerous failures of aluminum parts where there was a threaded fastner under a high torque load over a extened static load---(rods for one thing, rockers also)seems that the failure radiates from the threaded area of the aluminum Alum rockers should have the load relieved if sitting for extended periods |
Looks like it cracked on the tip side first, then the rear failed, see #2 photo. you can see where the surfaces worked before failing. Can't tell from the photo's 1,4,5 what or where the shaving? came from.
Not an expert, but isn't the shaft supposed to be installed with the oil hole down? or maybe they have 2 sets of holes ( top & bottom) They appear to be of cast material not billet, maybe not the best choice for the application? Craig |
I had one of my Dove HD rockers crack on the tip end. Did not break, but it sure did crack. I am really getting jittery about this rocker arm stuff. I do believe the Dove stands and end stands are good, but am beginning to wonder about the rockers. Since the Dove rockers are cast, would billet aluminum rockers be stronger?
Don't mean to hijack this post, but who has thoughts as to what rockers one would go to if the Dove HD's are replaced. I would like to reuse the Dove stands as they are already sized properly for my high rise heads. And, if the geometry of the rocker should be the same as the Doves, the push rods (which are new) would not have to be replaced. Erson's would need some machining on the stands. I don't like the smaller shafts of the Erson setup. T&D's would require machining on the heads and I don't want to have to pull the heads. Any thoughts? Priobe. Comp Cams has a push rod measuring tool and it is easy to use. Check their web site. |
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I had to do this to my rockers to prevent the cup of the pushrod hitting the rocker
http://www.clubcobra.com/forums/atta...1&d=1261345439 |
the ersons have torrigton bearings, a smaller diameter shaft and thicker material around the bearings
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Priobe ... you asked how to set your valve geometry . Rule of thumb I have always used is that when the valve is at 50% lift , the center line of the rocker tip/roller and the valve stem center line must coincide . At that point , good things happen . You can make your own adjustable pushrod by cutting an old pushrod in two , taking out a section and replacing it with a threaded rod . This will allow you to lengthen or shorten the pushrod to get correct geometry .... or you can buy one from a number of sources .
As far as rockers , I`m using the Sigs on my Cobra , however , someone on Club Cobra is selling a set that he says is a large step above the Dove , but not as expensive as the Sigs . I think it is blykins . I`m not real impressed with the Dove stuff . On my Galaxie with only moderate spring pressure and lift , I`m wearing the shafts and bottoms of the rockers at about 500 miles . There is another thread on Forefe.com on Dove equipment you might want to check out . |
Get in touch with Precision Oil Pumps. Great rocker, shaft and end stand setup available.
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I read a lot of posts about Dove quality. I'm sure some of it is justified, but I think a lot is hearsay.
In the interest of full disclosure, I have a Dove 427 aluminum motor (block, high rise heads, valve train, dry sump system, water pump, timing cover, etc). I owe Dove nothing, but I am happy with my motor. About Dove. Their website claims they are the worlds largest roller rocker manufacturer. (www.doveengineparts.com) I don't know if it's true but Dove says so. They might be right. Have you noticed how many rockers are shaped just like the Dove rockers? I know that Comp's rockers are private label manufactured by Dove. All I am saying is before people knock their rockers, take a moment and Google all the patents Dove owns on rockers. I have heard people "diss" Dove rockers, yet praise Comp's rockers...go figure. According to Dove, they have been manufacturing roller rockers since 1978 under the the Dove brand and according to their website "many name brands". I know I posted earlier having a problem with a cracked Dove rocker and I may go to another brand or I may not. I just think it is a good policy to only comment on manufacturer quality if one has first hand knowledge, not hearsay. Don't know why I felt the need to post this...but it needs to be said. |
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http://stores.precisionoilpumps.com/...ker/Detail.bok I think the dove rocker is stronger than the precision pump rocker, as the aluminum cross sectional area at the fulcrum is larger. The Dove rocker failed after several years. The precision oil pump rocker failed after several months. |
Personally I wouldn't use a rocker that ran alloy to steel contact.
My cars have stud mounted or shaft mounted roller rollers with caged needle bearing races. |
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