The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Marqs1979 on 07.12. 2013 17:12

Title: Renovating cylinder head
Post by: Marqs1979 on 07.12. 2013 17:12
Hello!

Can anyone tell me what width sealing surface of the valve which is optimal? I milling the valve seats on my A10


(http://forumbilder.se/CGD6D/img-7070.JPG)

Cheers / Markus
Title: Re: Renovating cylinder head
Post by: wilko on 07.12. 2013 21:48
Don't go too crazy with your valve seat cutter. Try just lapping the valves first to save some metal on your seats.   2 mm on the inlet and  3mm on exhaust is good enough.
Title: Re: Renovating cylinder head
Post by: Marqs1979 on 08.12. 2013 15:15
Thanks

Measured the gap on the valve guides and the cylinderhead in the picture was the gap up to 0.3 mm: (

I have one more cylinderhead where the biggest gap is about 0.1 mm. Is it good enough or should I replace the valve guides?
Title: Re: Renovating cylinder head
Post by: chaterlea25 on 08.12. 2013 16:22
Hi Markus ,
0.1mm (0.004in.) between the valve stem and the guide inner bore is on the wear limit
0.3mm is utterly Fu**ed

The guide bore should be 5/16in (0.312) and the valve stems are the required clearance below this figure

Make sure new guides are concentric to avoid excess cutting away of cylinder head material

HTH
Regards
John