Warning to engine rebuilders/overhauls-Important Info about Valve Guides
Posted: Tue May 23, 2023 11:07 am
I hope this information will help all people in the future.
I learned this the hard way, it turns out others did too viewtopic.php?f=7&t=18309.
When I brought my engine heads to the workshop, with all the assemblies shiny new (valves, springs, guides, etc.), I didn't have to ask him to do a good job. He is considered a leading workshop in the field and the whole country works with him. That's why I felt confident when I installed the rebuilt heads on my engine. After about 100 km I got stuck and needed a tow. Back home, lifting the RH engine head, I saw that the intake valve rocker arm was broken: the valve was stuck inside its guide. Oil reached the head and the push rod was full of it. To be on the safe side, I also pulled the LH cover, to find the following pictures. After consulting with the friends here and with Jan in the Netherlands, Salis BMW, I came to the conclusion that nowadays the workshops automatically ream the guides according to the tolerances accepted today, in the age of modern engines, but - it is important to ask them to give an oversize of 0.10 mm and to make sure that the valve stem does have a slight lateral play inside its guide. Mainly in a hot environment, which nowadays due to global climate change, most places on our globe, even in the relatively cold areas, already get there in one period or another, for a few days or weeks.
I learned this the hard way, it turns out others did too viewtopic.php?f=7&t=18309.
When I brought my engine heads to the workshop, with all the assemblies shiny new (valves, springs, guides, etc.), I didn't have to ask him to do a good job. He is considered a leading workshop in the field and the whole country works with him. That's why I felt confident when I installed the rebuilt heads on my engine. After about 100 km I got stuck and needed a tow. Back home, lifting the RH engine head, I saw that the intake valve rocker arm was broken: the valve was stuck inside its guide. Oil reached the head and the push rod was full of it. To be on the safe side, I also pulled the LH cover, to find the following pictures. After consulting with the friends here and with Jan in the Netherlands, Salis BMW, I came to the conclusion that nowadays the workshops automatically ream the guides according to the tolerances accepted today, in the age of modern engines, but - it is important to ask them to give an oversize of 0.10 mm and to make sure that the valve stem does have a slight lateral play inside its guide. Mainly in a hot environment, which nowadays due to global climate change, most places on our globe, even in the relatively cold areas, already get there in one period or another, for a few days or weeks.