Hi all,

I am currently rebuilding my M635 engine and its clear that the Valve Guides are worn beyond practical use. Where oh where can I get some of these things??? I have tried the Dealer Network (I work for a Dealer) to no avail as I am told they are no longer stocked by BMW. I have also tried GSF and also no luck!  One option offered to me was to use 12 oversize Valves for the exhaust side, but at £54 a go  I say no!

I would be very grateful to draw on your extensive knowledge for these particular parts.

Thanks in advance, Wheeler Dealer

An old chestnut this one I'm afraid.   BMW have never stocked valve guides for the M5/M635 head just over size valves as you have found out.

I understand that you can use VW valve guides but I don't know which ones. 

http://www.kormanfastbmw.com - www.kormanfastbmw.com do install there own valve guides so this may be a source if they will export.  You could also go to the S14 sites as the same guide applies to this engine.

Installation of new guides is I believe with guides at -300 deg C and head at +300 degree C.

How have you measured the tolerances?  With valve 1 inch out of seat the tolerance is a total of 1.2mm play side to side measured with a DTI(i.e. 0.6mm each side).  This is a massive tolerance.  Are yours over this tolerance?.  Mine were within but still had up to a total of 0.8mm play.  I think the installed tolerance is high to start off with.  More important to change out  valve stem oil seals to prevent oil loss under vacuum and whilst engine stands over night.

I had my head reworked with a 4 thou head skim and then valves and seats recut with a 3 angle finish.  Total for the machine work was £152 which is very reasonable.  They also used a special machine to centre the valve in the guide whilst cutting the valve and seat.  The machine takes up any play in the guide. 

Also are the valve stems OK (7.0mm I recall)  I doubt these have any appreciable wear.  I do have the full specs for my head prior to rebuild if you wish to compare.  Rebuilt engine has 2k miles on it now and runs fine. 

Cheers for now and let us know if you find guides.

Ian

Correction - try http://www.metricmechanic.com - www.metricmechanic.com not korman as korman supply vlaves not guides.

metricmechanic quote $7 per guide (in there engine parts pricing page) but you would need to get confirmation from them that they are for the m5/m635 head

Ian

Thanks for the postings guys, I am going to check all this information out.

James     

ian M635UK wrote: An old chestnut this one I'm afraid.   BMW have never stocked valve guides for the M5/M635 head just over size valves as you have found out. I understand that you can use VW valve guides but I don't know which ones.  www.kormanfastbmw.com do install there own valve guides so this may be a source if they will export.  You could also go to the S14 sites as the same guide applies to this engine. Installation of new guides is I believe with guides at -300 deg C and head at +300 degree C. How have you measured the tolerances?  With valve 1 inch out of seat the tolerance is a total of 1.2mm play side to side measured with a DTI(i.e. 0.6mm each side).  This is a massive tolerance.  Are yours over this tolerance?.  Mine were within but still had up to a total of 0.8mm play.  I think the installed tolerance is high to start off with.  More important to change out  valve stem oil seals to prevent oil loss under vacuum and whilst engine stands over night. I had my head reworked with a 4 thou head skim and then valves and seats recut with a 3 angle finish.  Total for the machine work was £152 which is very reasonable.  They also used a special machine to centre the valve in the guide whilst cutting the valve and seat.  The machine takes up any play in the guide.  Also are the valve stems OK (7.0mm I recall)  I doubt these have any appreciable wear.  I do have the full specs for my head prior to rebuild if you wish to compare.  Rebuilt engine has 2k miles on it now and runs fine.  Cheers for now and let us know if you find guides. Ian

Very good post.  That machining of your head was indeed cheap.  I do hope the workshop flattened the head under a press, before licking 4 thou off the mating face.  Mind you, if 4 thou was enough to clean it up, couldn't have had a lot of distortion anyway.

I agree that the Stem seals are likely to be at fault.  Try softening them with a Wynns product called Engine stop-leak.  If that doesn't do it, change the seals.  Mine have gone in 3 pots.  It could be the piston rings, but judging by the fact that one side of the Sparkplugs is getting crudded, leaving the other side near perfect, indicates the contamination is coming from a given direction. 

Thanks

Head was not placed in a press.  Not necessary unless you are building the ultimate track weapon.  BMW never did it on original manufacturer.

4thou was to clean the surface (it was not distorted) it just had a curious scratch on one of the water channels.

I have used the shop many times before (triumph 1500, dolomite sprint - in my youth you understand), they are genuine people and only charge £25/hr labour.  Never had any problems with them.  They may be asked to port my spare head in the near future.

Ian