What to do about a damage thread?
Discussion
I would some advice on my problem below, the engine is a 1.8vvc K series:
I’m changing from bolts to studs, to attach the exhaust manifold to the block, because there is one thread damaged, the one at the end of the engine near cylinder number 4.
The damage to the tread is such that I can feel it slipped when I trying to tighten it to the same setting as the 4 other one (hand tight).
To solve this problem I was going to use some threadlocker, Loctite 270, which is vibration proof, to lock the studs in place. Before doing so I had the idea of checking the technical spec of it and it says it will withstand temperature up to 250C.
So my questions are:
What temperature the block goes up too?
Does a high temperature threadlocker exist?
What are my other option? (will have to be done by me)
Thank for your help
Jack
I’m changing from bolts to studs, to attach the exhaust manifold to the block, because there is one thread damaged, the one at the end of the engine near cylinder number 4.
The damage to the tread is such that I can feel it slipped when I trying to tighten it to the same setting as the 4 other one (hand tight).
To solve this problem I was going to use some threadlocker, Loctite 270, which is vibration proof, to lock the studs in place. Before doing so I had the idea of checking the technical spec of it and it says it will withstand temperature up to 250C.
So my questions are:
What temperature the block goes up too?
Does a high temperature threadlocker exist?
What are my other option? (will have to be done by me)
Thank for your help
Jack
Most of the head only gets up to 120 or so, but in the region of the exhaust valve it can get hotter. On mine the exhaust primaries get over 500 C. I don't suppose the head will get this hot (and I don't think an alloy head would survive it if did) but it doesn't seem safe to assume that the studs will stay below 250 C.
You could try a thread insert, helicoil or recoil. I have recently used these for the first time replacing cylinder head bolt threads on a BMW lump. It's a bit of a stressful process, drilling in to an engine is not for the faint hearted, but it is very effective and you can be certain that the new thread is at least as strong as the original and temperature proof. You could also continue to used the original type bolts.
Is the engine in the car? If so you may have some problems with access as you need to get a drill in to the existing hole and fairly accurately.
I gather there are visiting services for this sort of work that garages use though I had no luck finding one local and prepared to do private work.
Is the engine in the car? If so you may have some problems with access as you need to get a drill in to the existing hole and fairly accurately.
I gather there are visiting services for this sort of work that garages use though I had no luck finding one local and prepared to do private work.
If the thread is stripped then thread lock will not help.
Helicoil/recoil is the answer unless you feel that you could just go up a bolt size. The constraint with the larger bolt will be clearance between the bolt head and any obstructions on the manifold. Again this could be resolved by using a hex socket cap head bolt.
Steve
Helicoil/recoil is the answer unless you feel that you could just go up a bolt size. The constraint with the larger bolt will be clearance between the bolt head and any obstructions on the manifold. Again this could be resolved by using a hex socket cap head bolt.
Steve
Wire thread insert is the best answer.
You can try thread lock with a new bolt/stud and also run a tap down the hole, I doubt that will last long but it shouldn't do any harm as you can always fit a thread insert afterwards. Don't be tempted to use the stronger stud lock which you won't be able to get out (that's my experience anyway).
Tapped threads in Ali are always a nightmare because of, the risk of pulling the threads out with over torqueing, ease of cross threading, and don't forget galvanic corosion (using stainless makes this even worse!). I'm not a fan.
IMO the proper method is to fit thread inserts from the beginning and I think that is what is done in aero engines. This is obviously too expensive for the mass produced auto market.
Leo
You can try thread lock with a new bolt/stud and also run a tap down the hole, I doubt that will last long but it shouldn't do any harm as you can always fit a thread insert afterwards. Don't be tempted to use the stronger stud lock which you won't be able to get out (that's my experience anyway).
Tapped threads in Ali are always a nightmare because of, the risk of pulling the threads out with over torqueing, ease of cross threading, and don't forget galvanic corosion (using stainless makes this even worse!). I'm not a fan.
IMO the proper method is to fit thread inserts from the beginning and I think that is what is done in aero engines. This is obviously too expensive for the mass produced auto market.
Leo
If you can get the component out of the car, your best bet would be to contact a local engineering shop (yellow pages).
They'll be able to put the whole lot up in a jig borer. You could do a re-bore while you are there! I doubt the actual job will actually be that expensive. Maybe only fifty quid. The real problem is getting it to them. This is what the aerospace people would do.
The wire insert might work.
If you can turn the stud/bolt past it's lock point by hand loctite won't work, irrespective of the temperature. If it's an anerobic adhesive as most of types are, they require the screw interface to come up tight to work.
They'll be able to put the whole lot up in a jig borer. You could do a re-bore while you are there! I doubt the actual job will actually be that expensive. Maybe only fifty quid. The real problem is getting it to them. This is what the aerospace people would do.
The wire insert might work.
If you can turn the stud/bolt past it's lock point by hand loctite won't work, irrespective of the temperature. If it's an anerobic adhesive as most of types are, they require the screw interface to come up tight to work.
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