Stripped Manifold Hole in Cylinder Head

[david.g.chapman]

I have a stripped thread in one of the manifold stud holes on a twin cam head. I have bodged something for now, but would like to helicoil it in the near future.

If I am not mistaken I need a 5/16 inch UNC insert about 18mm long. My question - is there enough aluminium around the hole to drill it out to take the insert? The head is a stromberg type with the smaller exhaust ports. I do not want to strike oil or water!

Dave Chapman.

[Frank Howard]

David,

There's probably plenty of material around the hole, but I know there is not much at the bottom of the hole. I speak from experience because I took a drill to mine and struck water! The aluminum is so soft, I thought I was cleaning out the remains of a stud but it didn't take much to go right through without realizing it.

A mechanic told me that many cars are built with the studs going right into the water jacket and he recommended some sort of sealer that is used for this purpose. It did the trick and I have never had a leak, at least in this area of the motor.

I do hope you'll never have to resort to this. Good luck.

Frank Howard
'71 S4 SE
Minnesota

[john.p.clegg]

Dave
I'm sure it's not standard but I'm sure i replaced the bolts with stainless studs locked in and used nylock nuts (fit and forget).

John

[cliveyboy]

Dave
If the threads have stripped and the stud has come out, you might be lucky enough to tap the new thread without drilling. I have done this once or twice when the threads have stripped out completely as the hole you need to drill is only fractionaly bigger than the diameter of the thread that has stripped. Just be careful with the helicoil tap not to cut to much at once and use lots of cutting fluid.
There are other thread inserts on the market which I tend to prefer.
They are more like a solid threaded insert and have tiny pins on the outside that lock the insert in place. Only down side is they are quite expensive.
Clive

[Jason1]

Guys

Has anyone tried this HTS 2000 stuff? Have a look at the link and watch the video on the top right of the page.

http://www.aluminumrepair.com/

The video is pretty impressive, if it is for real

Jason

[david.g.chapman]

Jason, that is one cool video. I suppose it is for real, although I find it hard to believe.

I will, however, try to make a repair without removing the head - just the exhaust manifold and the servo - so the idea of just using a helicoil tap straight away is attractive.
The offending hole is on number 1 exhaust port.

Cliveyboy, have you any more details on those expensive inserts?

Dave Chapman.

[Otto]

Hi

I have several times fixet my motorbikes head with Helicoil, without drilling! It is easy to feel, if if the tap goes too tight. I will recommend not drilling! It is easier to take material out than in! and the drilling part can easely make the hole too big or uneaven.

[cliveyboy]

I used some inserts a while ago (iirc) K- serts but I can not find any info on them.
The other alternatives are as mentioned Helicoil inserts or there are some similar type inserts by www.wireinserts.com
they do some inserts with a friction/locking design which will work better with studs as they will tend to stop the stud unscrewing when you undo the nut.

Clive