valve seat cutter question

[jimbaker]

I am considering buying one of the Neway Valve seat cutter kits. I am a bit of a tool junkie, have 2 cubs to do, one right now (the engine is apart on the bench) and the other eventually, so buying the kit is just fine. My question is that in reading the forum, I noticed most postings that deal with using the seat cutters cut a 3 angle profile. Originally, I believe the cub just had a single 45 degree cut. I am aware of the flow benefit in automotive applications of the 3 angle cut, but is it necessary and/or that beneficial in a cub? This is a pretty under rated engine, and inasmuch as the cutters are about $65 for each angle, and it seems like a but of an overkill to 3 angle the valves when the rest of the intake/exhaust is so restrictive. I am wondering if the single 45 degree cut would be sufficient.
Thanks in advance,
Jim

[John *.?-!.* cub owner]

I cannot answer your question, but do not overlook the fact that a cubs valve seats are cast as part of the head and not very hard. if they need much work they have to be cutout and new seats installed, You may want to think about the cutter head needed for that.

[Cecil]

I have a neway set and I use the 45 degree on all my valve jobs. I have done may and have never had a problem.

[Gary Dotson]

I cut all 3 angles. Seat area extending beyond the valve face area will often cause valve face erosion (ie burned valve), it's more about narrowing the seats than it is about performance. I suppose a Cub engine may not care that much but failure to narrow the seats on an automotive application is a sure recipe for a do-over. Yes, the cutters are expensive, I watched e-bay until I found a used set I could justify.

[Alan Riley]

I also cut all 3 angles using a Neway set. It cut the hardened seats just fine but I still lapped the valves to the seats to be certain of a good seal.

[gusbratz]

I have done many valve jobs on stationary natural gas engines, very similar to a cub but much larger (12-16" bore). I was taught to do an included angle, meaning the seat is like 45.5 and the valve is 45. ideally the contact pattern is high on the seat in the head and low on the face of the valve. since the angles are different this will provide a very narrow seat contact pattern. also as it wears the wear contact point will go up the face of the valve and down the face of the seat giving you a longer live. I never used carbide cutters always just a stone and stone dressing tool. I would guess and check with a blue check on my first valve till I got my grinding wheel dressing tool just perfect then I ground all the seats. I hope that helps. a picture would be worth a 1000 words here.....