Thread Repair Inserts for Aluminum Cylinder Head; aluminum, steel, or stainless?

[ls2005019227]

I'm working on a 2012 Bennche Bighorn 700x (think 2006 Yamaha Rhino 660), and the threads in a couple of the bolt holes in the aluminum cylinder head are stripped out (for bolts that hold the valve cover on). The original bolts are 6mm, and have a torque spec of 7.2ft-lbs; which was obviously exceeded at some point prior to my ownership. I know that Heli-coil is an option (I don't have any), but just planned on drilling/threading the hole in the head oversize (9mm) and making inserts (9mm O.D. [male] and 6mm I.D. [female]) to fit. Since this is an aluminum cylinder head, it will be subjected to heat, and I'm not sure what material would be best to make the inserts out of..... I have steel, aluminum (6061 & 7075), stainless (416, 15-5, & 17-4), and bronze, that I could use. I subscribe to the Tom Lipton's "Nothing too strong ever broke" mentality, and want this to be the first/last time that I have to repair these. What material would be best for this application? Any concern in using a dis-similar material (if that's your choice)?

I also planned to use Permatex threadlocker red for securing the inserts; is this viable, or should a mechanical locking method be used (if so, which one)?

Thanks for any replies/wisdom!

 

[CarbideBob]

Why is the easy way, Heli-coil or other brands not an option?
You want to make your own inserts? Going up to the next standard tap size that you have?
How will you peen or seat this in between part? What if it spins at torque?
Oh my Permatex red on a high temp area. I'm sure that will hold.. not.
If making such a plug use the same type material so that expansion and contraction the same as the base during the heat and cool cycles.
I also must say that you can get away all wrong and murder in what I see as as your application.
With that thought what is easier for you to make?
Bob

 

[Gordon Heaton]

Is there enough 'meat' in the head and valve cover to just go up a size? If not, I think the standard answer is an ordinary steel insert as mentioned by Bob.

 

[climb-101]

why go to the trouble to make an insert, i have used keenserts on a few four wheeler's that had issues like that. easy to put in and they cant spin.

 

[bsg]

If you have enough material to use an insert, I would go that route?

We use threaded inserts that have Loctite, it's activated during install....these are used on our engines that will see dozens of component changes.....one of the nice features, they come in several sizes, including metric/inch combinations!

I've used the Key-locking inserts for mag plates for vibration tables, they also work well, although the cost is a little higher.

Both inserts can be machined out if damaged!

Kevin

 

[kustomizingkid]

Timesert, quit trying to reinvent the wheel.

 

[ls2005019227]

I realize that Helicoil/timeserts/keenserts/machining my own are all viable options. Call it thrifty/cheap/expedient; but I prefer not having to wait or pay for something that I have the material and can make, in less time than it took to type my initial post. Also, it's an easy machining project that my 11yo son will enjoy in repairing this machine, while learning about metalworking.

I'm not looking to "get away all wrong and murder" or whatever point BrittleBob was getting at.

Although the original bolts are 6mm, there is plenty of meat in the cylinder head to drill oversize for an 8mm or 9mm insert O.D. I plan to keep the 6mm, to use the existing bolts and match the holes in the valve cover.

I had considered making the inserts out of aluminum to match the thermal expansion properties of the head, but obviously steel/ss would be much more durable. Come to think of it; Helicoil/Timeserts/keenserts are all steel of some sort, so it probably doesn't matter.

I'm not a fan of any threadlocker for semi-permanent installations, and much prefer mechanical locking. While it says that Permatex red is supposedly secure to 450°, and I don't think that the head gets that hot, I'm open to other options. With the valve cover, the insert couldn't back/come out; worst case scenario, it would seep oil. Peen the last thread? Drill for a pin? Other options?

Thanks

 

[moonlight machine]

I realize that Helicoil/timeserts/keenserts/machining my own are all viable options. Call it thrifty/cheap/expedient; but I prefer not having to wait or pay for something that I have the material and can make, in less time than it took to type my initial post. Also, it's an easy machining project that my 11yo son will enjoy in repairing this machine, while learning about metalworking.

I'm not looking to "get away all wrong and murder" or whatever point BrittleBob was getting at.

Although the original bolts are 6mm, there is plenty of meat in the cylinder head to drill oversize for an 8mm or 9mm insert O.D. I plan to keep the 6mm, to use the existing bolts and match the holes in the valve cover.

I had considered making the inserts out of aluminum to match the thermal expansion properties of the head, but obviously steel/ss would be much more durable. Come to think of it; Helicoil/Timeserts/keenserts are all steel of some sort, so it probably doesn't matter.

I'm not a fan of any threadlocker for semi-permanent installations, and much prefer mechanical locking. While it says that Permatex red is supposedly secure to 450°, and I don't think that the head gets that hot, I'm open to other options. With the valve cover, the insert couldn't back/come out; worst case scenario, it would seep oil. Peen the last thread? Drill for a pin? Other options?

Thanks

You are way over thinking this, you can have a helicoil kit tommorow from Mc Master Carr.
It will be fine and you will have it next time you need it. If you need to be hard headed about this at 7 lbs torque any material will work.

 

[Dan from Oakland]

Keenerts and timeserts suck. do what Moonlight suggested and save the Keenserts for when the helicoils fail, which should be never.

 

[Garwood]

Loctite red works just peachy on/in a cylinder head.

When a Ford Triton V8/V10 blows out a spark plug you can install a Timesert that mechanically locks and 3 months later it will loosen and get shot out with the spark plug again. Then you get to buy the Calvan kit that fixes the timesert failures and this time you use red loctite and it's permanent.

OP- teach your kid how to install a helicoil properly. That is a useful skill and so is teaching them what is and is not an appropriate repair for a given situation.

Machining an insert instead of buying a helicoil is not a good use of resources.

 

[moonlight machine]

Machining an insert instead of buying a helicoil is not a good use of resources.[/QUOTE]

No, it is stupid, prolly not the stupidest thing I have herd of but close.

 

[rons]

You probably can make an insert with a lot more meat than a helicoil and it will be stronger and not look like a dinky little spring.
But I would go for the helicoil first. If you use a helicoil the original thread will be stronger than aluminum and you will forget that it is in there.

 

[dian]

tap it m7.

 

[plastikdreams]

Why do they always have to twist people's names around?

 

[GregSY]

I usually, when using a new set of aluminum cylinder heads, drill out all the exhaust side bolts holes and Heli-Coil them (steel) before I ever use them. It's way easier than waiting for them to go bad and fixing them in the car.

 

[kustomizingkid]

Keenerts and timeserts suck. do what Moonlight suggested and save the Keenserts for when the helicoils fail, which should be never.

Why do timeserts suck?

 

[jim rozen]

tap it m7.

M7 X 1 thread works well in a stripped out M6x1 thread. You can purchase M7 fasteners.

 

[AlfaGTA]

Timeserts really are not good for blind holes unless the hole is much deeper than the threaded portion...Got to have clearance to run the insert expander past the end of the insert....
My take here is that the holes are blind.

So i agree with other posters that a Heli-Coil repair would be the best overall choice...
If you are determined to make inserts, then i would follow the lead of Hispano-Suiza and make the inserts out of bronze....(642)
20's and later Hisso's used bronze inserts for all the threads installed in their aluminum blocks...See original blocks to this day and the inserts are still working, never a problem with pulled threads on those engines,
but then they did have the best engineering /execution for the day...They are what Rolls Royce wished to be....

Cheers Ross

 

[ps123]

I you insist on making your own insert you need to consider how you are going to synchronize in the interior and exterior threads otherwise it might be prone to failure. Seems like helicoils is the way...

 

[Mark P.]

We did a ton of machining on magnesium plating. We used keylock inserts in the threaded holes. That is a different option.