How much heat can valve stem seals handle?

[Selfteaching Dane]

Hi guys!

I'm doing my CB 400 F rebuild. I'm painting the engine with VHT Aluminium paint, and I'm curing it in the oven. But how about my head and the valve stem seals? How much heat can they handle? Obviously they must be able to handle working temperature of the heads, so I could just cure it a that temperature, but what is it?

 

[NobleHops]

If you read the directions on the can of VHT (I know, I know), you will see that they advise curing for 1 hour at 200 degrees, which is no problem for any of the rubber parts in your engine.

 

[NobleHops]

P.S. I am assuming your engine is together, and that is why the valve stems seals are still installed. If I am wrong you really ought to replace those.

 

[Selfteaching Dane]

Thank you for the answer.

I believe my can says "Apply heat and gradually build-up to maximum working temperaure" - but 200 degrees Celsius has been the curing temperature for the other parts, so if that works for the valve and the head, I will continue to do so. (the paint so be able to withstand temperature op to 500 degrees celsius)

The engine is apart and the stems will be replaced. My concern is that I was planning on having a machine shop do the work on valve and so on and therefore having it painted either before or after (probably before)

And alternate solution is to remove the valves my self. Paint it and have the machine shop grind the valves and fit the new stems, but I haven't on that yet.

 

[NobleHops]

Whoa, the VHT I have used is cured at 200 degrees fahrenheit. Doesn't sound like what you're using. 200 degrees C is as they say, a horse of a different feather (could be just me that says that )

I'd personally strip the head, soda blast it, wash it clean, degrease, etch, paint, let it cure a few days, the bake it, then give it to the machinist. Worst he'll likely do is put a grimy fingerprint or two on it, easily cleaned back off.

 

[Selfteaching Dane]

I've decided to take out the valves myself. I thought it was to big of an task but after a YouTube video, I decided it could be that hard. I'm happy I did it. So I will do as you have suggested and not having to worry about what temperature my stem seels will brake.

200 Fahrenheit and 200 Celsius is af difference! the VHT I use claim to withstand heat up to 500 degrees Celsius.

 

[o1marc]

VHT Engine Enamels resist heat up to 550°F (288C). The directions say it is an air dry paint, but can be oven cured at 200°F (93C) for 20 minutes. It will cure on it's own from the engine heat during use.

Are you using something different?

 

[NobleHops]

I've decided to take out the valves myself. I thought it was to big of an task but after a YouTube video, I decided it could be that hard. I'm happy I did it. So I will do as you have suggested and not having to worry about what temperature my stem seels will brake.

200 Fahrenheit and 200 Celsius is af difference! the VHT I use claim to withstand heat up to 500 degrees Celsius.

Attaboy - good job.