pulled threads on valve cover bolt holes...heli-coil? brass?

ok guys...latest flub, checking my clearances (all good) w/o mechanic stand (stupid exhaust) and filled the left front bolt holes w/oil...snugged them down...keep turning ...whats goin on :? ...............omg 8O ....omg no! lol, cest la vie... so what do you guys think... i dont have alot of metal out there and i dont want to bugger her up to bad should i go with a heli coil? brass insert? any helpful hints dealing with either? and anyone use either with success? failure? thanks guys...this should be interesting

mike

 

Helicoil only way to go for the price , then Superglu

 

Re: pulled threads on valve cover bolt holes...heli-coil? br

Brass is too soft IMO. Helicoil is the cheapest and easiest way to go. I have a few different cast iron thread inserts that I like to use, but they're a bit pricey for a project where you're only gonna need one or two.

 

Sometimes you can get away with a longer screw. Likely you didn't strip the threads all the way to the bottom of the hole. I have done this with success on a couple of occasions that I stripped the head and oil pan bolts. You'll either get them to hold or strip the thread all the way down - but you have nothing to lose at this point.

Good luck!
Rob

 

Re: pulled threads on valve cover bolt holes...heli-coil? br

Helicoil is good for that ... spark plug holes dont like helicoils though ...
Anyway if you are doing more than 1 remmeber not to change the locations of the caps ... they are align bored to cam shafts ... and they wear together ...
Cool.
Srinath.

 

Why would you fill the holes with oil pryor to inserting the bolts.
That is a good way to split the bolt hole wide open. especially where the wall is so thin in that area.

I suggest coating the bolts with a thin layer oil, but don't fill the holes.

Just my $.02 cents

 

Yikes!! Yeah, I totally missed that part. Yeah, hydrolock is no fun, I've seen cast iron blocks crack like that. 8O

 

Heilcoil or longer bolt as mentioned before (depending upon location). Definitely do not fill holes with oil, bad idea with expensive damage resulting. Sorry to hear of your follies there Dude, we all learn or experience that one at some point, I'm no exception (try finding a fellow to heliarch your water pump housing at 4 pm on a Sunday afternoon).

 

Sorry I couldn't get the pictures to come up.


Forgot to reset the torque wrench after tightening the head bolts, eh? Now you've gone and stripped out the threads from that nice expensive aluminium casting...

Not to fear. There are ways to repair that head. The cheapest and easiest is to oversize the bolt hole and re-tap. But sometimes that isn't an option. Such as when the bolt is a special design...

Now you need a thread replacement kit. The most famous brand is Heli-coil. The old hole is drilled slightly oversize and a spring-steel thread insert is installed.

Here a 6mm thread is being replaced. First, the hole is drilled out to the specified diameter (1/4")
Next, the enlarged hole is tapped with the special Heli-coil tap. This tap comes in the kit and is the same thread pitch as the original 6mm, but the diameter is slightly increased to accomodate the enlarged hole.
The spring steel insert is installed into the hole using a special tool, also supplied with the kit. The design of the tool has changed over the years. Two different designs are pictured here.

Longer threads can be made by stacking inserts, installing the first one deep into the hole and then adding a second above it, but the standard length is usually sufficient in aluminium.
Both designs have one thing in common: they wind in the insert by driving the bent tang on the bottom. This tang is scored (visible at the top in this picture) so it can be broken off later if need be, but leave it in place until the insert is installed.

Since the insert is a spiral (kind of like a slinky) twisting it in contracts the diameter slightly. When the tool is removed, the spiral expands to grip the hole tightly.
Here the insert is installed with the tool into the prepared hole. This particular tool is designed to ensure the insert is inserted at least flush before the tool can be removed from the work.

Some mechanics recommend a little red (permanent) Loctite to prevent the insert from ever coming loose. If you go that route, use it sparingly and wait for it to set before installing your new bolt. Just in case a little leaks through the spiral...
Here's the insert installed into the hole. If you look closely you can just see the drive tang still in place at the bottom of the insert. Make absolutely sure the insert is deep enough (at least flush with the top of the casting) before proceeding to the next step.
Finally, a square ended drift is used to snap the drive tang off inside the hole. One quick rap with a hammer is all it takes.

Getting the tang out can be a little trickier in a blind hole. Since the engine was still in the bike, turning the part upside down and shaking really wasn't an option. A tiny magnet might work, but often a greasy q-tip is the simplest solution.
The special design of this bolts underscores the need to repair the existing hole in this case, rather than oversizing.
The kits come in a wide variety of sizes. While big expensive professional kits are available that cover a range of sizes, the backyard mechanic is probably better off buying small individually sized kits as needed.

They are still pricey, but at least you don't have to mortgage the house to afford one! Each kit comes with the tap and insertion tool appropriate for the size, as well as a few inserts to start off with. Extra inserts can be purchased separately as needed. Tap handles are not included. If you do not already have a tap and die set, you will need to buy a handle suitable for the size tap that came in your Heli-coil package. Oddly enough, sometimes the tap and the insertion tool need different size tap handles!

 

Also drilling aluminum can be a bit tricky. Be careful, the bit has a tendency to pull right into the work.

A drill press would be the ideal choice but that's kinda hard to do on the bike.

Drill as straight as you can and go no deeper than the original hole depth.

Also if you do use loctite I recommend to let it cure overnite, then gently run a tap thru to clean any that may have oozzed out into the threads.

Good luck.

 

Re: pulled threads on valve cover bolt holes...heli-coil? br

whoa whoa... i didnt fill the holes up on purpose... the bike has a 4-1 exhaust, the way it sits all of the oil in the head flows out the left front side... i just didnt notice as far as drilling straight is concerned, im no good at it but after taking 1/16th off of the bolts they sit in snug and the valve cover doesnt leak. now for a different question. the bolts on the opposite side in the front are pulling also, they didnt leak but they stopped going down about 3 lb's torque, the pit of my stomach dropped and i almost threw something but they havent leaked yet so im not inclined to replace them... why would the bolts on the front of the head be pulling so much easier? i normally screw them in w/ a nut driver before torquing, and i torque to the specs (7 lb's) i know the bike is possibly overheating due to paint (po) and lean conditions, could that cause it? why just the stupid front!!! :lol: sorry about my abbreviated first post, trying to give you a feel of what happens in my mind


thanks
mike

 

Re: pulled threads on valve cover bolt holes...heli-coil? br

Did you pull the valve cover when warm? I've seen aluminum threads pull out because people didn't wait for the motor to cool down, and hot aluminum strips much easier than room-temperature aluminum. Plus you have the extra heat from the exhaust on the front of the head. I dunno, just throwing some things out there. :wink:

 

Re: pulled threads on valve cover bolt holes...heli-coil? br

I pulled exhaust bolts when hot yesterday ... they were tight when cold, and I was worried they may be stripped ... I saw silvery crap around the threads ... They also had rusty head and flange ... was worried I'll strip that (BTW it was a GS500 with allen heads ... ) I got the motor hot ... riding for 20 mins, then turned it off for 20 ... exhaust got cold, but motor was warm, and head was warm ... and I opened them, it was easy, and the damn pipe hadn't seated fully in the head ... making it spit and leak ...
In some cases hot head is better I think.
Cool.
Srinath.

 

Re: pulled threads on valve cover bolt holes...heli-coil? br

Well, aluminum does expand more quickly than iron, so yes, it'll make it easier to break a bolt free, but for whatever reason (I'm not an engineer, so I can't explain it) the aluminum also seems to get softer as it heats up. So, I guess it's a toss up. Do it cold, run the risk of stripping the bolt head or breaking the bolt. Do it hot, run the risk of stripping the threads.