Stripped threads
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Stripped threads
After replacing a couple of bent pushrods in my 67' 352 i found that the threads in one of the holes for the rocker assembley had been stripped and would not tighen up. What are my options on repairing the threads? Is a heli coil the only one or is there something better?
Elder User
Joined: Jul 2003
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After replacing a couple of bent pushrods in my 67' 352 i found that the threads in one of the holes for the rocker assembley had been stripped and would not tighen up. What are my options on repairing the threads? Is a heli coil the only one or is there something better?
Go one size larger with a self bottoming tap. Cut the threads with cutting oil, and blow the metal chips and debri out with compressed air. Use a new grade 8 bolt of the same length as the original bolt. You may have to drill the rocker hole out slightly, if at all. "Form a thread" from permatex is an option as well. Either way, get a new bolt.
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Use a Heli-coil. The tap that comes with the kit will more than likely work without having to drill if the threads are actually stripped in the head and not just the bolt. Then use a new bolt (original size).
FYI, I have never striped the threads in a cast iron part, just the bolt and a clean up tap will fix any crap left in the threads.
FYI, I have never striped the threads in a cast iron part, just the bolt and a clean up tap will fix any crap left in the threads.
Elder User
Joined: Jul 2003
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FYI, I have never striped the threads in a cast iron part, just the bolt and a clean up tap will fix any crap left in the threads.[/QUOTE]
Trust me, it happens! Especially when treads are exposed to a water jacket or someone over tourque's a bolt. The threads are removed or barely there sometimes, then what..the thread material is all but gone. In this case, running the original size tap is about useless if one wants to use the proper torque of the original bolt. Also, I need to know, what exactly is a clean up tap? Taper/ bottoming, etc, I've heard of..
FYI, I'm just pulling your chain bear. Yes, cast threads get pulled all the time...One must experience things before saying it does not happen.and only one\your\our\my repair is the ONLY correct aproach to the problem is wrong. I just stated what worked for me in a pinch, several times in the past.
Trust me, it happens! Especially when treads are exposed to a water jacket or someone over tourque's a bolt. The threads are removed or barely there sometimes, then what..the thread material is all but gone. In this case, running the original size tap is about useless if one wants to use the proper torque of the original bolt. Also, I need to know, what exactly is a clean up tap? Taper/ bottoming, etc, I've heard of..
FYI, I'm just pulling your chain bear. Yes, cast threads get pulled all the time...One must experience things before saying it does not happen.and only one\your\our\my repair is the ONLY correct aproach to the problem is wrong. I just stated what worked for me in a pinch, several times in the past.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
FYI, I'm just pulling your chain bear. Yes, cast threads get pulled all the time...One must experience things before saying it does not happen.and only one\your\our\my repair is the ONLY correct aproach to the problem is wrong. I just stated what worked for me in a pinch, several times in the past.[/QUOTE]
Maybe I was lucky, but as a professional recreational saltwater marine mechanic, I probably saw more corroded blocks and heads (we won't even get into the exhaust manifolds on marine engines) than you can imagine. Of course very few boaters actually work on their engines, so maybe that's why I never saw any there. Also I was shown what a torque wrench was for and how to use it before I was in my teens, so that probably explains the rest of it.
Elder User
Joined: Jul 2003
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Also I was shown what a torque wrench was for and how to use it before I was in my teens, so that probably explains the rest of it.[/QUOTE]
That is probably #1 of all things one could teach another. Proper torque. I did not mean to say you were mistaken. One works in different fields and see's different things. I have used many helicoils and still have the kit's.
That is probably #1 of all things one could teach another. Proper torque. I did not mean to say you were mistaken. One works in different fields and see's different things. I have used many helicoils and still have the kit's.
Senior User
Joined: Feb 2006
Posts: 355
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On rocker bolts it is possible to strip the threads from being too loose - not enough torque. The movement of the shaft works the threads until they fail. I've also seen the wrong - too long - bolt bottom out and give a false torque reading - and the stripped threads follow.
Helicoil works well. An old rocker pedestal makes a good drill guide.
Helicoil works well. An old rocker pedestal makes a good drill guide.
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