Heli coil pulled out

First off I'd like to hi to all as this is my first post.
I just got it running when a oil leak appeared in the head 3 fins up where the 2 nuts are that screw down onto the studs nearest the pushrod tunnels. So I took the head off to do the sealing of the 2 studs.
While I was looking at the head on my bench I noticed that one of the head studs which a long nut goes to was pulled out of the head.
No big deal if this was the first time but this stud was repaired once already with a heli coil. It is the heli coil that pulled.
Now I have this big hole where a heli coil used to be.

Phil Radford did the Heli coils years ago and I called him yesterday but he is going on holiday to a rally for 3 weeks.
He does all my work and does it well. I might have over torqued it.

Does anyone have a solution for my problem?

Guido this is competent shop work ,research the proper helicoil thread size to prevent mistakes. Or I assume you live in California ? so there are others who can help there. BTW you can run a head with this missing stud and have no probs. by using a copper head gasket and copper hi temp silicone but seeing as head is off get it fixed. Torque re manual and again after 50 to 100 miles. Peter

Thread inserts are much more robust than helicoils and I think is your solution if there is material within the casting to do this. Seems to me that I have heard of others doing this with all studs in alloy all over the bike, particulaly the primary inner mounting hole that often strip out. I believe that there will be meat to drill and thread as the outside thread of the insert is much bigger than the helicoil thread.

The question is if you want to remain stock as this size may prove a little more difficult to find, not that they're not available, just harder to find. Someone here will direct you, i'm sure.

Threaded inserts will be applied with JB weld and this issue will never rear its ugly head (so to speak) again. Might as well do left and right while you are at it.
From what you say I think you are talking about the front left and right stud with the nut that is applied from below?

Drill out and tap 5/8 UNC or 16mm.or what ever ,then screw in a brass insert and re-tap. Fixed for ever :lol:

Welcome to the forum, Guido.

Unless you are in a rush, why not wait till Phil gets back?

otherwise, [?????]'s advice is solid.

Wouldn't that be a bronze insert?

Dave
69S

When one of those studs pulled out on my bike a friend made a stud from bar stock that was made oversize regarding the portion that went into the head, but otherwise stock from there on down. It sounds as if when your helicoil pulled that you'll be in the market for something like that or an insert. I've seen inserts made of bronze used in just this application too. It would be important to find someone who is a good machinist AND one that knows Norton heads and their problems.

john robert bould said:

Drill out and tap 5/8 UNC or 16mm.or what ever ,then screw in a brass insert and re-tap. Fixed for ever :lol:

Click to expand...

You make that sound so simple which it probably is.
I am going to wait for Phil to get back and have him read this thread as an insert seems to be the best solution for my problem.
It is the 2 front studs that go into the head and are tightened by the 2 front long nuts from under the barrel.
I just had Phil do the valves and had just got it running and went for a ride when I noticed all the oil coming from the head at 3 fins up where the 2 nuts which are located thru the 2 bores in the from of the head.
Phil said, and I have read, the oil leak could be coming from the 2 studs which go into the barrels in the front next to the push rod tunnels and that from case pressure causes it to rise up the studs and leak where the 2 nuts are in the front of the head.
That is why I pulled the head in the first place, in order to remove those studs and reseal them with locktite to stop the leak.
That is when I noticed the heli coil had pulled.
I will have Phil fix the head but am really considering buying one of those new heads from CNW for the God awful price of $2200.00 and using the fixed head for my other '73 cmdo.
I kinda robbed the '73 for the '74.
If someone knows of someone in the Sacramento area competent to do this work, let me know.
Phil was not sure how to fix the problem and said he'd have to come up with an idea when he sees the head.
If I had a set of whitworth taps I know I could do it myself as I have the know how. I build racing VW engines as a hobby.
So, you would tap in a bronze insert which is 5/8 UNC where the thread for the stud is smaller than the head stud size, drill the insert and tap it to the size of the stud with a whitworth tap and call it good?

Try Rabers in San Jose. They may be able to help you. (408) 998-4495.

Brass expands at a simular rate to alloy. but is stronger than the head material. i renewed all eight exhaust studs on a Suzuki 850 GS . drilling and with the aid of a jig re-tapping. If your Heli coil as pulled out you will end up doing something like this. and yes it will last donkeys years.

DogT said:

Wouldn't that be a bronze insert?

Dave
69S

Click to expand...

Bronze or good brass. makes no differance. but if you want to be fussy. Titanium :shock:

Yes, titanium that's what's in my neck too, holding my head on. Pun intended.

Dave
69S

I'd like to post a pic but don't know how to upload to this site.
The FAQ's don't help much

Guido said:

I'd like to post a pic but don't know how to upload to this site.
The FAQ's don't help much

Click to expand...

technical-information-section-how-post-photos-t2357.html

My first pic post.



Now that wasn't so hard.
As soon as I get this bike on the road I'll post more pics.
Thank for all the help guy's.
I really appreciate it.

I keep inserts in 3 sizes and custom studs to repair your damage. I can take care of it after I get back from NY.
If the person who welded in the exhaust thread inserts was not careful in maintaining a safe cylinder head temp then keeping a stud in that hole can be tough. I would recomend a very coarse thread into the aluminum to get the most strength. Jim