Stripped cam cap bolt hole

[Guest]

I have a stripped cam cap bolt hole in my head, its one of the ones with the locating dowel. Can I put a heli-coil in it? Is there enough room with the dowel there too?

[Suzuki_Don]

Yes, you can heli coil that bolt hole, but you need to drill deeper into the head beyond where the dowel ends. When you are drilling you will feel when you get to the bottom of the hole as the pressure gets greater on the drill and the drill will stop cutting.

When fitting the heli coil it must be short enough to fit below the dowel and must be screwed in so the top coil is below the bottom edge of the dowel.

[gearhead13]

I measured the dowel at ~8mm vs the bolt which is 6mm, only 2mm to play with. What size tap and drill is used for a 6mm heli-coil?
I also have a 1/4" coarse tap here I could use with a new bolt. Much cheaper and easier for me because it is stuff I have on hand already, but would it be strong enough

[Coady]

You could try the 1/4 inch tap first, but there may not be much of a thread for the bolt to grip. If it tightens to the right torque spec without spinning and the other 3 bolts are fine then you should be right.

I found the $30 bucks for a helicoil kit to be money well spent and good piece of mind however. Especially since when I pulled the cams to fix 2 dodgy threads, another two bolts stripped as I was putting the cams back in - both on the outside cap holes so I could helicoil them with the head still attached.

I reckon, in hindsight, there's a good argument for replacing all the threads with helicoils too.

And you use a 1/4" drill for the 6mm helicoil. Don't know about the tap.

[rapidray]

You can use a 1/4-20 tap & bolt but I like to keep everything metric on my stuff. Go to a NAPA auto parts store & buy a 6mm x 1.0 helicoil kit. It will come with the drill bit, tap, insert tool & inserts. Ray.

[Suzuki_Don]

I measured the dowel at ~8mm vs the bolt which is 6mm, only 2mm to play with. What size tap and drill is used for a 6mm heli-coil?
I also have a 1/4" coarse tap here I could use with a new bolt. Much cheaper and easier for me because it is stuff I have on hand already, but would it be strong enough

How many TPI is the course 1/4" tap. A 6mm bolt is 25.4 TPI, so a UNF is 28 TPI and I think a UNC is 20 TPI. You could try the 1/4" course tap and see if the bolt will torque down to specs. If not then you will probably still have enough meat left to drill it out and insert a heli coil.

[cyclefvr2]

be careful! when you tap them you can go through the other end ,and it will leak oil, i did that accidentally on my old kaw, i went a lil 2 deep and cracked the head case ,and didnt know it , yea it leaked oil
some heli kits come with the tap ,and coils,and a tool , but when your done they work well

[SqDancerLynn1]

usually coarse 1/4/ 20 or fine 1/4 /28

[JEEPRUSTY]

You can use a 1/4-20 tap & bolt but I like to keep everything metric on my stuff. Go to a NAPA auto parts store & buy a 6mm x 1.0 helicoil kit. It will come with the drill bit, tap, insert tool & inserts. Ray.

man rapidray espousing metrication that is quote a statement

but then Im 30 yrs behinds the times.

[pete]

I can't comment on the actual hole you need to repair the thread in, but I can definitely vote for the helicoil method.

I stripped a bolt hole in my crankcase the other week and fixed it with a helicoil and not only was it straight forward (with lots of care), but the thread actually seems to be a little tougher with the helicoil than just with the alloy.

[tas850g]

You can use a 1/4-20 tap & bolt but I like to keep everything metric on my stuff. Go to a NAPA auto parts store & buy a 6mm x 1.0 helicoil kit. It will come with the drill bit, tap, insert tool & inserts. Ray.

+1 on ray's suggestion. When i was working on a ninja i got i had to do 2 heli coils on the cam caps. Used the kit ray mentioned and it worked great. Put some red lock tight on the heli coil and screwed it down in the new hole. Let it dry for 12 hrs just to be sure. Torqued it to specs, no problems.

This was my first experience with the heli coil and it was pretty easy.