Valve guides

[Rust bucket]

Started work on a good used standard 12G940 head for my 1098 engine, however the exhaust valves are not 8mm deep they are all around 7.50mm, would it take forever to grind that .50mm off the seats with just paste? also it needs a few new exhust valve guides as well, are they the same as 1098 minor ones? thanks.

[bmcecosse]

It would indeed take 'for ever' to get them down using grinding paste..... You need to use a 45 degree countersink - in a pillar drill - or of course a seat cutting tool. At 7.5mm you are at 300 thou...... You will get away with that - the head gasket will give the clearance - although it's a close thing... I know some have taken 10 thou or so off the face of the valve as a means of getting a little extra clearance -and DO set the valve gaps at a loose 15 thou. New guides from the likes of Minispares/Minisport. You need to judge how much wear there is - are the valves sloppy in the guides?? I would leave well alone unless v sloppy.

[MarkyB]

You need a valve seat cutter, something like this;
http://www.ebay.co.uk/itm/Sykes-Pickava ... 1e8433f706

You might be able to borrow or hire one.

[Rust bucket]

Okay I' ll have the exhaust seats cut by a local guy who has done work for me before, yes at leased two guides have lots of play at 1/4 open, thanks all for the info.