Topic: Helicoil Help

[Phoenix]

With little experience, I'm about to helicoil the four 6mm bolt holes that hold the cam caps down.  It's a recessed hole that has a dowel pin in it.  The dowel pin is about 8mm and a 1/4 inch bit is used for that makes it kind of tight.  I was told my a Honda mechanic that it's easy to screw up the hole and make it hard ton fit the dowel pin fit.  I even considered leaving the dowel pins in while drilling the holes.  Any suggestions would be greatly appreciated.
Thanks

[hsas.69]

Go slowly and make sure you drill as strait as possible. I like putting grease on the drill bit to catch shavings.

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[PeWe]

Good idea to drill in a perfect 90 degree angle. If stud will lean in either direction, the cam holder and caps will be hard to mount.
Easier to use a drill with cam holder in place to have a guide.
Do not use a machine, tap holder is OK with a sharp drill, I think 6.3 mm.

Use Loctite to lock the thread insert. Clean thread when cured, use high temp thread sealer in threads when tighten the studs, short threaded side into head. I blocked the hole from the ign plug side after studs were tightened. Head upside down, JB weld to plug the hole to avoid eventual future oil leaks

Time sert work better than helicoil.  Cost more though

[madmtnmotors]

Okay, we're talking bolt holes at the rear, not the stud holes in the front? If so, you need to be aware that there is a distinct difference between the stud holes (in the front) and the bolt holes (at the rear):

>The stud holes are drilled all the way through to the open cavity in the exterior of the head below. This requires that thread sealer be used when installing these studs to prevent oil weepage.

>The bolt holes on the other hand, are "blind bores" in that they are not drilled all the way through into the external cavity in the head below. Although these holes are not drilled all the way through, there ain't much material between the bottom of the bolt hole and the external cavity below. This is a much bigger issue for the bolt holes than it is with the stud holes because the oil feeds for the cam bearings pass through the bolt holes in the cam towers. If you look down through the bolt holes in the cam towers (not the stud holes) you will see the oil feed holes. If you "break through" the bottom of these bolt holes into the external cavity below you have the potential for creating a profuse oil leak because the upper part of the bolts are surrounded by high pressure oil that can easily be pushed past the bolt threads into the external cavity of the head below. These holes can be compromised by mixing up the middle tower bolts (longer) with the shorter bearing bolts and cranking down on the longer bolt until the bottom of the bolt hole gives way.

I pulled one engine four times chasing this very oil leak that would "oil down" my shins with hot oil within the first five miles. I ended up using studs at the two compromised bolt holes and used thread sealer on them when installed. This will be an even greater issue if you "break out" the bottom of these bolt holes since you will have to seal both the repair threads as well as the bolt threads too. So be careful when drilling and don't drill too deep. A drill press would go a long way towards keeping the bore straight and true as well as being able to limit the depth of the hole being drilled.

[MRieck]

Those are tricky Ed. As was mentioned...you have to measure depth. You need a drill press to drill the threads out. I have a special tap holder that fits into the drill press to ensure the tap runs straight. I use the tapered tap first (with lube) and then the STI bottoming tap. You must use the bottoming tap or the coil will get caught in the taper and jam the bolt when you try to screw it in. I use the Recoil coil driver and made a tool to keep pressure on the coil when inserting it. If you don't keep pressure on the coil it will jump threads.
 It's a bit tricky is what I'm getting at. I will get those studs out this weekend.

[Jerry Rxman Griffin aka MuthaF'er]

Exactly as Mike says. I did mine today with the head on. We'll see how it works when I go to torque it down tomorrow.

[Phoenix]

Mike. I was able to get two studs locally from CycleRecycle so don’t need them. Just got done with the job. Had a somewhat anal friend who’s building a airplane help me out. Measure about five times and used the drill press. After drilling, wasn’t much of a shoulder left for the dowel pin but it worked. Had to replace two of the studs that had the upper threads boogered. Might have been the double nuts. Used permatex as suggested. Will find out tomorrow how the Helicoils work when I start putting things together. THANKS FOR ALL THE SUGGESTIONS. VERY HELPFUL.