Helicoil, bugger!

[britishrallying]

Hi peeps,

Got a prob, last week or when ever it was, when removing the exhaust manifold the last stud gearbox end snapped. Drilled it out and thought I had got away with it, stud tightened up ok, well so it seemed!

Last night put the manifold back on and tightened all the bolts up got to the last one in the sequence, which was the problem stud, as it torqued up the stud pulled out of the head and stripped the thread oh well never mind these things happen.

I have a couple of options:

1. Chemical Metal
2. Helicoil

Chemical metal is the cheapest and quickest option but helicoil seems the best long term option. Which would you reccomend? has anybody else tried these options before on an exhaust stud?

If I go the Helicoil route, what size do I need? am i right in thinking its a M10 with a pitch of 1.25?

All this because nobody else decided to have a fiddle with the engine in the last 14 years! take it apart every year keeps the threads rust free :lol:

Cheers

Gaz
www.britishrallying.com

 

[rayman75]

i would recommend heliciol matey.

 

[cojack]

How bad is fella you should just be able to re-tap it with a thread tap :?:

 

[britishrallying]

Quite bad mate! sort of no threads left. Saw my hoop to be honest, thought i'd got away with drilling the snapped stud out, but must have slightly damaged the thread.

Put some Chemical metal in the hole with the stud last night, will see what its like this afternoon, torque it up if it holds then will try that but if not helicoil it is!

Like you say could re tap it next size up and just get an oversized stud, but dont really want to weaken the head.

On the bright side get gearbox back today

 

[Fast Guy]

Like you say could re tap it next size up and just get an oversized stud, but dont really want to weaken the head.

It shouldn't weaken the head. All you do for a helicoil insert is re-tap the hole a bigger size to suit the insert, then the screw the helicoil in and it steps the thread down to the correct size.

 

[britishrallying]

Ordering on from here tomorrow:

http://www.toolsnextday.ltd.uk/Helicoil_Kits/helicoil_kits.htm

Measured the thread, and the exhaust stud is defo M10 x 1.25 pitch £37 though for the helicoil, oh well better than the mani blowing.

Got gearbox back today, bearings replaced for £220, internals are in very good condition, the bloke said the car must be on low milage, just the low quality jap bearings was the only problem! happy days, car back on road the weekend hopefully!

 

[jiw]

Fitting helicoils makes it stronger, they helicoil aluminium in the aerospace industry as common practice where high torque figures are used for tightening.

Your stripped thread should be ok as the tapping diameter for the helicoil is the major diameter of the thread it is replacing, jeff

 

[britishrallying]

did the helicoil, got the engine back in this morning and the car feels like new now, with a new clutch and new bearings in the box!

Well happy now, no gear crunching

Even more happy as it was the first time ive ever took a whole engine out on my own, used the guides on this forum and my own initative 8) and jobs a good un!!

Cheers for everyones help over the last few weeks!!

Gaz