Thread Inserts Question

Thanks Barney! This is great.

LTGTR, You're welcome. Just take your time, don't force anything that doesn't feel right and try to keep things as clean as possible.

I'm still waiting for my replacement rings from Australia so mine isn't back together yet either.

I have new 40 over pistons and rings now, but everything works great now. i am going to hand lap the valves and install new valve seals. Keeping the new pistons for when I really need them.

I was thinking about this, will the insert length (12mm) be different for a 650?

BARNEYHYPHEN wrote:

The problem as I see it with the second builder's opinion is that you have to be absolutely sure that all POs actually DID torque the bolts correctly. Not a bet I'd take.

If the POs DIDN'T torque them correctly, the aluminium English) thread in the head WILL be stretched.

The reason I did all mine was because, although I was VERY careful to torque mine correctly the last time I did the job, I still stripped two of them. At that time I decided to over tap them to 7mm x 1mm. My thinking was that at some time in the future (now) I would still have enough "meat" left in the head to do the inserts.

Just my $0.02 worth.

UPDATE: The new builder informed me that he was installing heli-coils in 3 or 4 of the holes because they stripped when he was torquing down the cams for a bench shim. I bought the head used, so I'm sure someone has overtorqued the bolts at some point. I asked him to please go ahead and do ALL of the threads while he was in there. I don't want to have to drill, tap, and install after it's all together. Much easier to do and clean with the head apart. He has since told me that he does the heli-coils on race engines, but not usually street. I think inserts of some kind are almost necessary if you are going to have it apart with any frequency at all. Having a shim under bucket set up, my cams are out everytime I adjust the valves. Hopefully the heli-coils will hold as well as the nut-serts I had in my other head.

Thats a good write up Barney, Im thinking that it might be a good idea to do my head while its off too. Preventing future problems is a good thing
Anyone know if the inserts are the same on 650s? (do we use 12mm too?)
Scott

77KZ650, It won't totally negate all future thread problems but I do believe it gets you back to a good solid thread. Not sure on the lengthnyou should use for the 650 but Ii'd bet a dime to a $, the 12mm long inserts would be perfect.

You might measure the thread length of one of the bolts to give you an idea how much thread in in the head?

I just contacted an auto shop and they told me that the helicoil kit does not come with a drill bit!? Can anyone tell me what size drill bit I should be using? Thanks.

the kit should tell you what size you need.

The Helicoil KIT does come with both the correct drill and the correct tap. I will mic' the drill tonight for you if I can remember. Helicoil carefully doesn't tell you the size, they call it Helicoil #2 or some such BS, so you feel obliged to spend $8 for a new bit from Helicoil, rather than buying the same size bit for $1.75 at HD.

Helicoils for 6mm require a 1/4 inch bit.
Use a stop collar or some duct tape on the bit.
Make sure you drill and tap deeply enough. Look at the tap. The bottom 3 turns or so does not cut full thread depth. You'll have to drill deeply enough to account for this. If your squeamish you can spend some extra $ for the helicoil bottoming tap.
NAPA carries packs of 12 inserts at a good price. If not in stock, it will be there the next morning.
If you're really cheap you can make your own tool by grinding the end of a long 6mm bolt. Alignment of the tang holder is somewhat critical. It has to end on the thread. After a few attempts it's pretty easy.
You need the helicoil tap. It's not a standard size.

-Duck

you can cut the end off off tap to make a poormans botteming tap.:whistle: