Thanks Mike, the picture posted successfully this time. More pictures would be good - I'd like to better understand the shape of the top of the valve guide, and the matching recess in the top of the cylinder/head casting. Because the valve guides are not replaceable on that engine, I can't find pictures of the guide on the internet.
Well done on getting a recommendation (and sample) from Loctite. 640 it is only rated for 175 degrees Celsius. I keep a pack of their 620 for jobs like that - it is rated for 230 degrees Celsius, and is "For permanent assembly of shafts and bearings". However the 620 has high viscosity and requires a thick film, where the 640 can be used between press fit sleeves, which is exactly what we have here. Most likely the Loctite people were concerned to make sure you end up with a film of the adhesive, despite the tight fit between the guide and the cylinder head.
That guide has really come out a long way. Looks like we'll be relying fairly heavily on the Loctite to keep it together in future. By the way, note that 640 is a slow-setting formulation, because they want you to have enough time to press the parts together carefully before it sets - please don't run the engine in the first few hours after pushing the valve guide back into position, so the adhesive will have developed some film strength.
