820.030 Flavia 2000 coupé engine problem

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Huib
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Posts: 1796
Joined: 17 Dec 2008, 10:12

820.030 Flavia 2000 coupé engine problem

Unread post by Huib »

We just rebuilt a Flavia 2000 engine. Runs beautifully after starting. We can put an euro coin on its side on the air filter. But after some time the bolts for the rocker support of cylinder 4 come loose. And the helicoils / threaded bushes come out. Already when torquing the wrench does not click as sharply as on the bolts of the other 3 rocker supports.
Flavia-head.jpg
Flavia head 1.jpg
Flavia head 2.jpg
Flavia head 3.jpg
Any idea about the cause is welcome.
viiking
Posts: 21
Joined: 20 Aug 2020, 04:54

Re: 820.030 Flavia 2000 coupé engine problem

Unread post by viiking »

I have found helicoils are not good for SOME places on alloy engines. You don't say the brand of what you call "threaded bushes" but the best inserts according to many in the VW scene ( I have interest in these cars as well) are made by "Timesert".

These have a much better locking mechanism than other thread inserts and particularly helicoils. VW engines being originally a magnesium/aluminium mix can become very soft after 50+ years so there are lots of stories about helicoils in particular failing on head bolts and other threaded inserts failing but not Timeserts.

The Timeserts need a special tool to install. Google timesert and you will see a video. You have to drill a larger hole than for a helicoil but that shouldn't be a problem on your application.

Why only one cylinder has a problem? Could just be that whilst you can get the correct torque for the bolt does not guarantee that the insert has sufficient holding power if the insert is either loose or poorly inserted.
viiking
Posts: 21
Joined: 20 Aug 2020, 04:54

Re: 820.030 Flavia 2000 coupé engine problem

Unread post by viiking »

Any further news?
Huib
Site Admin
Posts: 1796
Joined: 17 Dec 2008, 10:12

Re: 820.030 Flavia 2000 coupé engine problem

Unread post by Huib »

Not really. Not yet

I sent both heads to one of the machine shops I work with. The aluminium was tested and found to be in excellent condition. Most likely the thread was damaged before by over tightening or tightening against a loaded valve spring.

Inserts for the full length of the hole were made with special thread on the outside. All assembled with M8 10.9 bolts. They are now on the way back to me.

More news in a week or so.
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