Broken Rocker arm adjusting nut-500efi
10-19-2006, 06:54 PM
#12
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Re: Broken Rocker arm adjusting nut-500efi
Originally Posted by Strip Poker 388
lifters are crane 16535-16,dogbone style 456.00..you might ck with RM builder on some of his ,but you might have to change the push rod length?
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10-19-2006, 07:14 PM
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Re: Broken Rocker arm adjusting nut-500efi
I had a few ARP rocker arm studs break one season. I believe they make different overall lengths and/or the threads for the adjusting nuts are threaded farther down on the studs on some.
Anyway, I found the correct ARP studs to where the rocker arm ball was down past the threaded area of the stud when properly adjusted. I don't believe that they were longer studs, but just less threads at the top.
Problem solved, and I didn't change pushrod length, just found the correct studs. I'm running big solid roller cams for RPM's.
I know this wasn't your exact problem, but something to watch for nonetheless. I didn't even ask my engine builder. When I saw where they were breaking, common sense prevailed.
Good luck. Valve train problems can make your ears "Twitchy", if you know what I mean.
Anyway, I found the correct ARP studs to where the rocker arm ball was down past the threaded area of the stud when properly adjusted. I don't believe that they were longer studs, but just less threads at the top.
Problem solved, and I didn't change pushrod length, just found the correct studs. I'm running big solid roller cams for RPM's.
I know this wasn't your exact problem, but something to watch for nonetheless. I didn't even ask my engine builder. When I saw where they were breaking, common sense prevailed.
Good luck. Valve train problems can make your ears "Twitchy", if you know what I mean.
10-19-2006, 09:07 PM
#14
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Re: Broken Rocker arm adjusting nut-500efi
Originally Posted by cstraub
RM's take the same length pushrod and are not limited on lift like the dog bone OEM stuff.
Chris have seen or heard of this type of failure??????
I wonder if ARP makes the ajusting nut [poly lock],There prob a better quality than Cranes.But to me there has to be someting that is causing them to break. They run these rocker arms with nuts on all kinds of race motors of all kinds,
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10-19-2006, 09:14 PM
#15
Re: Broken Rocker arm adjusting nut-500efi
Originally Posted by Tricky919
I'm going to do mine also, should i do head gaskets?
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10-19-2006, 10:26 PM
#17
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Re: Broken Rocker arm adjusting nut-500efi
No the break was around the top right below the hex nut on both. I will to get some pictures.
I appreciate all of the help from everybody.
I appreciate all of the help from everybody.
10-20-2006, 01:13 AM
#18
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Re: Broken Rocker arm adjusting nut-500efi
After a lifetime of adjusting poly-lock style rocker nuts the same exact way ,last year I had 3 different comp products rocker nuts split right below the hex around the circumference. They appeared too be crappy ,imported metal that was brittle. The first one I thougt was just a fluke and I caught it while pizzing around with my motor after dynoing it. The next one happened when out breaking in my motor the day after sotw on my first real ride in boat after installing the motor,it backed off and started clattering but caused no damage. Like a DUMBAZZ I fixed just the broken nut,grabbed my old crane gold rockers and nuts then went on vacation thinking if I had any more problems I would just change them all. Well ,I wasn't so lucky,after being on vacation a few days a third one broke allowing pushrod and lifters to mangle themselves 
. The minute I pulled in my driveway after returning I tore the manifold off to the lifters,luckily the cam and block were not damaged,I installed a set of arp nuts and have not had any problems since then. The arp nuts are even thinner where the comp ones were breaking which is hard to believe. I tighten them the same exact way I always have which is a little tighter than you should BUT it has NEVER been a problem on 50 plus other motors other than one set of cheap imported harland sharps on a pontiac were the nut cracked the same way and one nut was missing part of the metal brand new out of the pasckage,so I blame cheap nuts. Buy a set of arp nuts and forget about it. I am installing T&D shaft rockers this winter but I haven't had ongoing valvetrain problems since changing the nuts. The cracks in the nuts would allow the allen lock to loose its tension and they would back off but the wouldn't break all the way around,the nut wouldn't even look broke until tightened back down when the crack would open back up. The nuts Raylar was using in one of his kits had some failures too if not tigthened exactly as specified but I heard he had problems with a vendor that were fixed too,Smitty
. The minute I pulled in my driveway after returning I tore the manifold off to the lifters,luckily the cam and block were not damaged,I installed a set of arp nuts and have not had any problems since then. The arp nuts are even thinner where the comp ones were breaking which is hard to believe. I tighten them the same exact way I always have which is a little tighter than you should BUT it has NEVER been a problem on 50 plus other motors other than one set of cheap imported harland sharps on a pontiac were the nut cracked the same way and one nut was missing part of the metal brand new out of the pasckage,so I blame cheap nuts. Buy a set of arp nuts and forget about it. I am installing T&D shaft rockers this winter but I haven't had ongoing valvetrain problems since changing the nuts. The cracks in the nuts would allow the allen lock to loose its tension and they would back off but the wouldn't break all the way around,the nut wouldn't even look broke until tightened back down when the crack would open back up. The nuts Raylar was using in one of his kits had some failures too if not tigthened exactly as specified but I heard he had problems with a vendor that were fixed too,Smitty
Last edited by articfriends; 10-20-2006 at 01:22 AM.
10-20-2006, 08:23 AM
#19
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Re: Broken Rocker arm adjusting nut-500efi
Wow, I appreciate tjhe reply. That helps alot. That is exactly how my nut cracked also. Do you have the ARP part number available that you used. Thanks
10-20-2006, 11:39 AM
#20
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Re: Broken Rocker arm adjusting nut-500efi
There are 3 different arp part numbers for 7/16 studs.Comp rockers (like I have) use a .550 dia shank below the hex to clear the rocker body,this makes the nut paper thin,part # 300-8245.You need to measure the crane nut shank,I think its .600 in dia,ARP part # 300-8246 which is thicker. Comp products-1-800-233-0199 has them for 50$ a set. This a good investment,Smitty
