Frank - What size inserts do you/did you have?

I've got some M8 x 15mm
BUT, there's a slit cut into them at the bottom edge (they're self tapping)

Because of this slit, despite being 15mm long, there's only 7mm that I can use


(yes, I can screw further into them, but then I'd have a gap/hole between the insert and the set screw, meaning the set screw wouldn't even plug the hole)

 

There are "do it your selfer's" and there are "do it to your selfer's"; if you keep going the way you have been you will be the latter for sure. Drilling holes off square, drilling through a water jacket all gets complicated and expensive.

If it were me I would pull the head and fix it right to avoid future problems. Even if you just drill and taped it, it would be so much easier.

If you were to just drill and tap it I would go one size larger that you can helicoil to the proper size but run a plug of the larger size that is locked and sealed into place with red loctite. Helicoils make for stronger threads in aluminum and they are readily avalaible.

If it were me I would tap, weld and then helicoil. Its a Porsche not a lawn mower... Fix it right!

 

Hi Ant,

I'm not going down to the workshop for the next few days , but I will have to have a look then.
I do have M8's and there called Re-Coil inserts. They are similar to Helicoils except the teng at the bottom is different.
Can you post a pic up of the ones you have?
A a rule you need minimum of 1.5 X bolt diameter of thread in the hole for a secure fixing.

 

Engine Guy - could you expand on your previous post please?

My plan is to drill and tap it and install an insert, but i need to block off the hole to stop it from leaking too

What do you think would be the best way to do this?

And when you mentioned welding, did you mesn aluminium welding the head, or something else?

I asked on here about removing the head to fix this, but everyone said it was over the top and that i would be better of repairing the hole

 

Here's a picture of the inserts that I've got

They're M8 x 15mm
But, the slit in them means that only 8mm maximum is continuous

 

I see what you mean. I prefer Re-coil inserts TBH. If I was you I would buy some M8 x 12mm Re-coils, if you can manage 15mm then fine. Re-coils in Aluminum are stronger than just Aluminum threads.

 

Ant,
I would try a threaded insert by Timesert. The inserts come in all sorts of metric sizes and various depths. It is a fantastic product and the kit comes with a drill bit, tap and a special installation tool. I would go this route....

Timesert.com

 

Thanks mate

I'll definitely look at those
I can't see the inserts that I've got at the moment being up for the job

They're 15mm in length



But, as they're self tapping they have a slit in them
This gives them an uninterupted thread of 8mm



If I use the insert, I'll probably have to run a set screw into the bottom of that rather than fitting the screw into the head and installing the insert afterwards



However, due to the slit in the insert I can't screw the setscrew in any further than 8mm, otherwise it would have a gap and wouldn't act as a seal/ plug as it would need to

If I were to screw the setscrew in further than 8mm this is what would happen



And obviously, if I screw it in less than 8mm to ensure it's sealed I won't have much thread for the manifold bolt to screw into


I'm getting pretty close to admitting defeat now

 

What about reducing the legnth of the set screw. Remove the extruding portion in the last pic.

 

Hey Paulie

The part of the stud which extends past the bottom of the insert isn't a problem
I only screwed it down that far to show there will be a gap where the 'slit' in the insert is

I could back the screw up in order to get rid of the gap, but I would then be leaving myself with only a very small amount of thread for the manifold bolt to screw into - 6mm maybe 7mm maximum


I'm wondering if it's possible to fit the setscrew first (as the end part of the thread in the head is fine) this would plug the head (As shown in one of the earlier pictures) and I could then fit the insert afterwards - thereby keeping the 'plug' and the insert as two separate entities

 

I've just got off the phone with the garage that carried out my last service
I haven't got much confidence in them, but I thought id use them as a starting point to get an idea of how much it would cost to hand it over to someone else

They quoted me ~ £2,200 to remove the engine, flip the entire unit over, and alloy weld the holes with the head still in place

I think that works out to be around $3,500

 

You don't want to take the engine off yourself and remove the transmission and transport the engine to someone who can do the welding? You did so much work so far, I think you should carry on and save a little bit of men hours.... Of course if your shop agree about that...

 

Forget about welding the holes. Pure aluminum and certain alloys weld up nicely, generally casting alloys are full of silicon, mag, copper, zinc, tin, etc. This makes them difficult to weld. Also it's very hard if not impossible to weld in the bottom of a hole. It's hard to weld where contamination from coolant is a problem. A good weld requires preheating the part, which is impossible here. The heat required to weld up the hole may cause shrinkage of the head in the localized areas, also if enough heat is generated the interference fit of the valve seats can be lost and they may loosen and fall out. Your head will ruined as will your entire motor. I'm certain you can find several welders that will attempt this and ultimately screw it up and make a bigger mess than you already have.

I think in desperation you're looking for the easiest solution, and I think you're on track except for the fact you have to deal with water/steam under pressure. A simple set screw in the bottom of an open hole glued in with RTV and an insert or bolt screwed on top of it will not hold back the pressure.

For a permanent repair, anything else is just a temporary band aid, you need what I described in my earlier posts. A tapered pipe thread plug that has a wedge effect whereby the threads jamb together and mechanically effect the seal. Any added locktite, thread sealer, antiseize, RTV, etc is just a preventive measure to curtail any weeping afterward.

I think doing this is over your head and you should enlist the services of a pro. It's not necessary to have someone with Porsche or even automotive experience do this. I could easily do it and it would take probably between 1-3 hours start to finish for both holes. So I'm thinking if you find the right person it would be very cost effective to farm it out.

 

What is it you would like expanded on.

The one way is to tap the hole to a larger size all the way through and use a short plug to seal the water jacket. I would use red loctite on the plug not RTV or anything else like that. For double insurance you could liquid metal and cap on the back side after the plug is installed and dried. I would rough up the surface before doing the liquid metal cap. Then install a helicoil to the right size for your head bolt. A timesert would not be the right thing for this fix due to the flange on them. The flange would have to be recessed for to allow for the face of the header to mate up properly.

If you need to tap anything there are blind Taps.. The allow you to tap holes that dead end. Here is an example. http://www.emuge.com/taps/enorm.html

My first choice would be to weld and then tap. Despite what someone said above the head would not be hard to weld for a good welder. The antifreeze is not even and issue at all. I weld aluminum motorcycle rads all the time that are pop can thinkness and they have antifreeze in them. Antifreeze is not an issue!!!!!!!!!!!!!

Your best bet is a good welder and a machinist if you do not have the skills yourself. I am sorry this is not a hard fix, it is just one that takes time; and as we all know time does cost.

 

Thanks Nick

The reason I was thinking of using a set screw rather than the tapered screw that you mentioned was that I didn't want to have to enlarge the hole any further

Since trial fitting the set screw though, it's pretty clear that I'm going to need to use an insert anyway, so it looks like a taper plug is the way to go anyway

One thing I'm still concerned about though is whether it's possible to tap too far with the tapered tap and messing things up even further


As far as the job being over my head, - Yes, I think it's definitely too much for me

Like you said before, it's not a difficult job, but you need to have the experience if you're going to do it correctly, and this is something I am lacking

Unfortunately I don't know any good garages or machinists, so I thought I should do the job myself - My thinking was that I could do the job slowly and take my time getting it right - I guess I got that massively wrong also


How does the old saying go?.......

You can't make an omelette without drilling a few holes in your cylinder head


I'm going to look at the tapered taps again, but I think it's about time I admit defeat and try searching around for a good garage