Valve lapping and seat inspection

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assembled
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My Cars: 1991 Citroen BX TZD Turbo
1989 Citroen BX GTi 4x4

Valve lapping and seat inspection

Post by assembled » Wed Aug 06, 2014 12:32 pm

Hi, I am going through a XUD7TE rebuild and have yet another particular question.

One exhaust valve sea looks like this:
Image

I have tried hard, but pitting is too deep to remove by lapping. Also, looking at the pitted edge seat closest to head surface an edge can be noticed. This particular seat is slightly off-center towards camera.

How bad is this?


P.S. As this is not the first nor last question in this rebuild, maybe I should simply start a blog topic? Please advise.
1992 TZD Turbo berline, aircon, ABS
1991 TZD Turbo berline
1989 GTi 4x4 berline, ABS

Tinkley
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Re: Valve lapping and seat inspection

Post by Tinkley » Wed Aug 06, 2014 6:41 pm

You probably need the technical document for this engine. It will give the valve seat width and cutting angles. The normal cutting angles are 45 and 30 degrees, and then lapped to a perect fit.
Valve seat cutting gear is not cheap, last time I looked some years ago around 600 quid. So for this a specialist is probably cheaper. But try and find the data for the seat geometry first. It should also give max permitted wear.

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citsncycles
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Re: Valve lapping and seat inspection

Post by citsncycles » Thu Aug 07, 2014 12:33 pm

Off centre wear may mean issues with either the valve or guide. If you're just going for an engine that should run OK then so long as you end up with a smooth ring around the seat the valve shoud seal OK, otherwise as mentioned machining or even a replacement seat may be needed, which will require specialist machinery. Where are you based, as there are various companies round the country that members here have used.
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assembled
Confirmed BX'er
Posts: 79
Joined: Thu Jan 05, 2012 2:21 pm
Location: Arendal, Norway
My Cars: 1991 Citroen BX TZD Turbo
1989 Citroen BX GTi 4x4

Re: Valve lapping and seat inspection

Post by assembled » Thu Aug 07, 2014 7:14 pm

Thank you for your input.

I'm from Lithuania... But there is a great company to go to for a job like this. I shall get exhaust seats done.
1992 TZD Turbo berline, aircon, ABS
1991 TZD Turbo berline
1989 GTi 4x4 berline, ABS