LA1
Well-known member
I had a rocker arm bolt strip pulling out all the threads, probably going to use a heli coil...any suggestions on thread repair or drilling the hole
best way to drill a straight hole
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Notgrownup
Well-known member
Replace with one that is not compromised...
dlcwent
Member Emeritus
Permatex "form a thread" if you don't want to pull it and send if off. It has more than enough strength for the torque required.
redwrench60
Well-known member
GM 3.4 V6 blues huh. The repair recomended by GM for that is a Time Sert. Properly done it will be more than strong enough and won't require pulling the head but you'll have to use caution and control where the metal from drilling and tapping goes. Tape off oil drain holes and surround the area with oily rags to catch shavings. A good steady hand and a slow turning drill is all you need.
Techie1961
Well-known member
A couple of additional tips. When you are drilling, put some grease in the flutes of the bit and then also on the tap. This will hold onto some of the chips and the rags should do the rest.
Next, use the original hole as a guide. Have a friend help out and try this method. Place a drill in the hole that is the same size as the stripped threads. Get some coat hangers and cut off a few pieces. Bend them up and screw them onto the valve cover holes so that they are in alignment with the drill bit when viewing from the front and the side of the car. Get your friend to look at the alignment of you holding the drill and keep it visually in line with the two coat hanger fixtures. Do the same thing with the tap for the helicoil.
Next, use the original hole as a guide. Have a friend help out and try this method. Place a drill in the hole that is the same size as the stripped threads. Get some coat hangers and cut off a few pieces. Bend them up and screw them onto the valve cover holes so that they are in alignment with the drill bit when viewing from the front and the side of the car. Get your friend to look at the alignment of you holding the drill and keep it visually in line with the two coat hanger fixtures. Do the same thing with the tap for the helicoil.
pepi
Well-known member
Putting in a heli coil, you are only enlarging a hole that is already there by a few thousands. Unless one is a complete dufus with tools the drill will follow the hole that is there.
Check the depth and mark the bit with a piece of tape. Need only to go in enough so that the heli coil is in the hole below the surface.
Very easy to do, I would manage any metal chips common sense tells ya that.
With aluminum it becomes important to have a torque wrench and the mfg spec for the bolts, prevents these things. Even more so with the plastic intakes found on cars today. Cheap insurance is another word...
Check the depth and mark the bit with a piece of tape. Need only to go in enough so that the heli coil is in the hole below the surface.
Very easy to do, I would manage any metal chips common sense tells ya that.
With aluminum it becomes important to have a torque wrench and the mfg spec for the bolts, prevents these things. Even more so with the plastic intakes found on cars today. Cheap insurance is another word...
e30bradley
Well-known member
Use a time-sert! Heli coils ****. The hole should be drilled by hand using a tap wrench. I bought 2 mitutoyo tap wrenches $$$$$$ Now I have no excuses for damaging something while trying to tap threads or drill a hole or whatever.
fnieto
Well-known member
Heli coils have a place in the repair world and do not ****. That said, Time cert will work better for this application. Like mentioned, take caution in recovering chips.
All good suggestions. I would use a time-sert or at least a helicoil before pulling the head.
When drilling it out, have an assistant hold a shop vac next to the drill and cover the rest of the head with tape, rags, something to keep the metal chips from falling it.
When tapping it, coat the tap with grease and most of the metal will stick to it.
When drilling it out, have an assistant hold a shop vac next to the drill and cover the rest of the head with tape, rags, something to keep the metal chips from falling it.
When tapping it, coat the tap with grease and most of the metal will stick to it.
Techie1961
Well-known member
Helicoils are very good if they are installed correctly. Time-serts seem like they are excellent as well and I really like the expanding feature once installed. I read though that time-serts are soft. If that is true (it must be for the expanding feature to work), helicoils will stand up to wear a little better. They will definitely be harder than aluminum though. Helicoils will also offer you the option of going to time-serts for a second repair if needed since the time-serts need a larger hole. Time-serts should be better for a really buggered up hole.
It would appear that both have advantages and disadvantages over the other.
Techie1961
Well-known member
rlitman
Well-known member
Anything a Heli-coil can do, a Time-sert can do better.
That being said, as there is no need for a gas pressure seal in this application, either would be acceptable, and Heli-coils are both vastly cheaper and more readily found locally.
As suggested above, have a friend spot you while you drill. You can only see the drill from one angle, so it may appear perfectly straight, but still be off. If you have two people looking at the drill from 90 degrees apart, you'll easily get it close enough.
As for chips and debris getting in the engine, the answer is to cover whatever you can. Grease is great on a tap, but will fling off of a spinning drill bit. You could always have your helper hold a shop vac next to the bit while you drill to help.
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This assumes you need to do this in place.
1) Time sert vs Helicoil. They use the same taps. So they take out the same amount of metal. They also need the same drills and have the same issues drilling and tapping square.
2) To drill straight, you need the following:
2a) you need a stiff+short+sharp drill bit with the right coating & finish.
2b) To tap straight, you need a close-tolerance hole. This means no wobble in the drill. Check for oribital slop. If driling by hand underzide the bit by 1/64.
2c) Buy and use a drill guide and a tap guide. Time sert has a tap guide, its $7 extra + you buy it alone. Not in the kit.
2d) Practice. Buy some aluminum square stock.. It is sticky. It is very hard to dill square by hand because of this. Will grab drill bit.
2e) Use the right cutting fluid for aluminum.This will reduce grabbiness.
3) Buy extra inserts. practice using the drill guides and the tap guides and test your ability to free-hand drill tight tolerance holes. Then do the same for tapping the holes.
The time-sert kit will seem like a rip-off.
But you need a bunch of stuff that is not cheap to do this right.
The STI tap in particular needs to be very good quality and designed for aluminum, not steel.
Good luck. Hope this makes sense.
1) Time sert vs Helicoil. They use the same taps. So they take out the same amount of metal. They also need the same drills and have the same issues drilling and tapping square.
2) To drill straight, you need the following:
2a) you need a stiff+short+sharp drill bit with the right coating & finish.
2b) To tap straight, you need a close-tolerance hole. This means no wobble in the drill. Check for oribital slop. If driling by hand underzide the bit by 1/64.
2c) Buy and use a drill guide and a tap guide. Time sert has a tap guide, its $7 extra + you buy it alone. Not in the kit.
2d) Practice. Buy some aluminum square stock.. It is sticky. It is very hard to dill square by hand because of this. Will grab drill bit.
2e) Use the right cutting fluid for aluminum.This will reduce grabbiness.
3) Buy extra inserts. practice using the drill guides and the tap guides and test your ability to free-hand drill tight tolerance holes. Then do the same for tapping the holes.
The time-sert kit will seem like a rip-off.
But you need a bunch of stuff that is not cheap to do this right.
The STI tap in particular needs to be very good quality and designed for aluminum, not steel.
Good luck. Hope this makes sense.
max 2NM torque. this is a no-go.
shockwave
Well-known member
grap a drill bit the size of hole to center a starting point and use reverse drill bit to remove broken stud with threads intact
try this before talking timesert heilcoil
try this before talking timesert heilcoil
APEowner
Well-known member
This is not that big a deal to repair in place. I like Keensert inserts if there's enough meat but a good old fashioned Heilicoil will be as strong or stronger than the original threads. Which ever you use you'll have to work at it to not have the drill follow the existing hole.
bmxdad
Well-known member
What about a keensert, which are made for soft material? If I remember right, you only need to drill a hole a little larger then a heli-coil ... looks to be a little cheaper too.
YES I got those 3.4L Bluuuues. I have heard of the time sert . I think I am going to check all the other rocker arms to see if they are torqued properly . I have a 1/2' drill that is variable that turns really slow . I was thinking of working my way up in drill bit size . the pedestal that the rocker arm sits on, drilled out would make a guide if I can find another one, it has that grove in the bottom that fits in the vertical grove that goes through the bolt hole.
good idea will try that
LOL Drill right threw the head. Yeah I believe they were over torqued , the plastic intake manifolds...what are auto makers thinking of. there is a vid on you tube where one exploded.
I Don't think the drill guide will fit in the limited space. I was thinking of finding another pedestal that the rocker arm sits on, has a grove in the bottom that fits in the grove in the cylinder head. going to drill it out and cut it down maybe. probably will not use any guide if I cant clamp it down.
I Just found that I have some M8 X1.25 HELI Coils left over from my motorcycle days. I believe that is the bolt size. if the heli coil does not work I will use the keenest since it requires a bigger hole. I still need to check the rest of the rockers to see what condition they are in.
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