- Joined
- Jun 24, 2010
- Messages
- 2,444
- Reaction score
- 967
Finally found time to organize pictures off my camera & quick update. The valve making/seating journey continues, but I think (hope) I have a general plan & procedure now. Im finding theres a lot of variables to this aspect, at least at my skill level.
I made a different vacuum gauge tester to compare valve seal against a known seat reference. For example if valve A draws down slowly over say 10 secs (a good seal) & valve B draws down in only 2 secs (a bad seal) then I know valve B requires remedial work. Hopefully this will give me comparison reference across all my valves. This tester has a tap on the chamber side connected to the vacuum gauge hose. The valve stem side is blanked off with a silicon blind. This way Im not introducing any added sealing effects from valve stem/hole annulus by drawing vacuum on the end (original tester). This effect typically made my seal results look better than reality & introduced another variable. Now, the only seal the vacuum sees is the valve seat itself.
I learned a few things with this method. Machining the valve faces introduces the typical micro troughs from just basic turning. Terrys magnified pics show this really well. If these arent polished off completely, seal is hard to achieve consistently. My homebrew lapping methods were not working great, but probably a function of my technique. The best results was actually the simplest, just wet/dry paper + WD40 on a backing stick until the face was nicely polished progressing up to 1200+ paper. I wish I had a microscope or something more powerful, but my 10X eye thingy was good enough.
I was originally concerned about exactly preserving the original 45-deg valve face. Meaning I didnt want to polish my way to a slightly different angle & create a new problem. Im finding there is a bit of wiggle room here. You cant be too crazy off, but I got pretty consistent results by hand method. I felt penned the face, polished it off until no more color & repeated. Actually I have a theory here. I may well be introducing an ever so shallow arc effect across what was a straight line seat section and maybe thats even helping the valve find its tangent contact point & seal that way?
The Brownell seat cutter was a love hate thing. I just had to be more patient & develop a feel for how it was cutting. It just needs a feather touch & few more rotations vs. trying to rush it. Any downward pressure results in generating some ugly undulations that get progressively worse to point of no return. Everything else related to this is exactly as Terry mentions. Ill use the original tester on production mode cages, but at least Ill feel more confident about the pre-tested valves.
So as a result, my new & improved valve seat plan is going see significantly less valve cage chamfer distance than plans called for resulting in valves protruding deeper into the combustion chamber vs. more flush to the dome. Im slowly picking off those issues now. The cages needs to be more submerged in the head & maybe valve heads thinned a bit.
I made a different vacuum gauge tester to compare valve seal against a known seat reference. For example if valve A draws down slowly over say 10 secs (a good seal) & valve B draws down in only 2 secs (a bad seal) then I know valve B requires remedial work. Hopefully this will give me comparison reference across all my valves. This tester has a tap on the chamber side connected to the vacuum gauge hose. The valve stem side is blanked off with a silicon blind. This way Im not introducing any added sealing effects from valve stem/hole annulus by drawing vacuum on the end (original tester). This effect typically made my seal results look better than reality & introduced another variable. Now, the only seal the vacuum sees is the valve seat itself.
I learned a few things with this method. Machining the valve faces introduces the typical micro troughs from just basic turning. Terrys magnified pics show this really well. If these arent polished off completely, seal is hard to achieve consistently. My homebrew lapping methods were not working great, but probably a function of my technique. The best results was actually the simplest, just wet/dry paper + WD40 on a backing stick until the face was nicely polished progressing up to 1200+ paper. I wish I had a microscope or something more powerful, but my 10X eye thingy was good enough.
I was originally concerned about exactly preserving the original 45-deg valve face. Meaning I didnt want to polish my way to a slightly different angle & create a new problem. Im finding there is a bit of wiggle room here. You cant be too crazy off, but I got pretty consistent results by hand method. I felt penned the face, polished it off until no more color & repeated. Actually I have a theory here. I may well be introducing an ever so shallow arc effect across what was a straight line seat section and maybe thats even helping the valve find its tangent contact point & seal that way?
The Brownell seat cutter was a love hate thing. I just had to be more patient & develop a feel for how it was cutting. It just needs a feather touch & few more rotations vs. trying to rush it. Any downward pressure results in generating some ugly undulations that get progressively worse to point of no return. Everything else related to this is exactly as Terry mentions. Ill use the original tester on production mode cages, but at least Ill feel more confident about the pre-tested valves.
So as a result, my new & improved valve seat plan is going see significantly less valve cage chamfer distance than plans called for resulting in valves protruding deeper into the combustion chamber vs. more flush to the dome. Im slowly picking off those issues now. The cages needs to be more submerged in the head & maybe valve heads thinned a bit.
