When I was working on my radial engine, I was confronted with 18 stainless valves that all needed to seal, and anyone who has done this knows it can be a PITA and frustrating at times. I decided early to create valve guides/seats of aluminum bronze that would combine guide, seal, etc into a monolithic unit. These tend to be easier to fabricate and seal rather than working directly with a cylinder head. A bonus is that if valve or guide doesn't work, they can be replaced.
Rather than install, then test, I decided to create a tool that would allow me to test the seal before it was installed in a head. I also made use of special abrasives (TimeSaver lapping compounds) that are guaranteed not to embed in the softer bronze. Very effective abrasives.
The valves were worked with their dedicated guide, and then installed into this aluminum turning:
At the bottom is a simple hose coupler for compressed air. At the top is a turned area for an O-ring:
Obviously, the device needs to be air-proof in all areas except for normal valve actuation.
On top goes a threaded cap to compress the o-ring and tighten everything up:
It is crude but effective. To test the general sealing capabilities of the valve + guide, apply a few (10 to 30) PSI to the device, and simply listen. There will almost always be some tiny leakage, but your ear can easily determine (for example) "this valve + guide is excellent; this one needs additional work." Of course, pressing on the valve stem with a punch or similar will actuate the valve, and you can check the action easily.
Once done, the valve + guide should be paired. A light engraving (or using a sharpie marker) will do this.
Overall, this setup worked well, and I was able to make 18 valves and guides, plus a couple of spares, that I had confidence in. Hope this gives people some ideas.
Rather than install, then test, I decided to create a tool that would allow me to test the seal before it was installed in a head. I also made use of special abrasives (TimeSaver lapping compounds) that are guaranteed not to embed in the softer bronze. Very effective abrasives.
The valves were worked with their dedicated guide, and then installed into this aluminum turning:
At the bottom is a simple hose coupler for compressed air. At the top is a turned area for an O-ring:
Obviously, the device needs to be air-proof in all areas except for normal valve actuation.
On top goes a threaded cap to compress the o-ring and tighten everything up:
It is crude but effective. To test the general sealing capabilities of the valve + guide, apply a few (10 to 30) PSI to the device, and simply listen. There will almost always be some tiny leakage, but your ear can easily determine (for example) "this valve + guide is excellent; this one needs additional work." Of course, pressing on the valve stem with a punch or similar will actuate the valve, and you can check the action easily.
Once done, the valve + guide should be paired. A light engraving (or using a sharpie marker) will do this.
Overall, this setup worked well, and I was able to make 18 valves and guides, plus a couple of spares, that I had confidence in. Hope this gives people some ideas.
