Crosman exhaust valve repair

I recently got a new project rifle, a Crosman 766. I bought this rifle to see if I could make it into a bulk fill CO2 rifle. 

That Blog should be next....

Once I got the rifle apart I found this, a crusty exhaust valve with a crumbling seal. I have a couple spare exhaust valves but the stems would need to be shortened and they don't have the brass body. I'm not sure if the brass makes the valve any better but having the extra metal in the valve makes me feel better. 

Here is the exhaust valve as it came out of the 766, It's sitting in the pliers for display purposes. 

I used a couple cheap Chinese pellets to protect the stem while I clamped it in the vice. I should really invest in some soft jaws for my vice. With the valve secured in the vice I used my butane torch to heat up the body. 

The stem is a press fit in the body and the heat expands the body enough that it can be pried off. I tried to be careful but still managed to put a couple dings in the body. The small dings wont really cause a problem since they don't affect the  sealing of the valve.

I cleaned the crud and corrosion from the stem and body. With everything clean I measured for the replacement seal, .310" OD the hole for the stem is .14" and it needs to be .062" thick. 

I had some options for seal material, Delrin, PTFE or HDPE (High Density Polyethylene) I went with HDPE for my first attempt since it is a bit softer than Delrin or PTFE. Turned to the correct diameter and the hole bored I parted off a  new seal.

The seal was a good fit in the body. 

I used my arbor press to re-install the stem in the body. 

The rebuilt valve.... 

I didn't really expect this to work on my first attempt, much to my surprise once the valve was put back together and installed in the 766 it held air. Now I can get on with trying to get the 766 to run on CO2.