I'm going to put modern valves in and called Neway to order valve seat cutters. I was going to cut them 15' 46' & 60'
But Neway says I don't necessarily need to cut a 15 degree.
Would you recommend a 15 degree cut on the seats too?
I'm open to any thoughts or even a different opinion on the best way to cut seats
That's the set I have and I use all three. The only reason I can think of why they would tell you that is the 46-degree is supposed to be so in the first several seconds of running, the fine contact of the 46-degree seat vs. 45-degree on the valve face sort of laps, or beds-in, on its own, but I think this applies more to newer engines with higher spring pressures. I still cut the seat to the desired width and give them just enough lapping in by hand to make the contact I want. To achieve that width, I still find it necessary to use the 15-degree cutter in the event I need to raise the bottom of the seat.
I was informed long ago that the 45/46 degree faces helped prevent buildup on the seat/valve faces causing valves to be held open a hair.
Did they recommend using a 30 degree in lieu of the 15?
The typical 3 angle valve job is 30,45 (or 46),and 60. Some high performance racing engines will use 5 angles, 15,30,45,60 and 75.
The 30 and the 60 angles are used to manage the seat width and where on the valve face the seat makes contact.
I was not thinking on my initial reply. My set is 31, 46, and 60 and, of course, 31 does the top.
I don't know how you'd do the job without the top cutter. Without larger diameter valve heads you'd have the seat all the way out to the margin.
(Message edited by WMH on March 14, 2017)
The 30 degree angle isn't always necessary.
I use all three to get the seat where I want it on the valve face and also to control the seat width. I don't know if it is really necessary on a T block, but you really should not have the seat face too wide.
Gary's last sentence is right. That is how you control the location and width of the seat to the valve.
I have a Neway valve seat cutter set purchased for Model T valve seats. I have a combination cutter head of 31 and 46 degrees. I also have a single 60 degree cutter head. The combination cutter has 5 blades each side, the 60 has 3. I am happy with the combination head but would not recommend the 60 because it has only three blades. 5 blades is the way to go.
One more tip. You will need to use adjustable pilots for the two oversize valve stems. Make darn sure the pilots are clean from grit when tightening them down. If any foreign material gets into the mandrels, the cutter angle will be affected and you will not get a good job. Very important.
In my experience the 60 degree cutter is not very important on T seats. The 31 and 46 definitely are.
I got a set from Neway two years ago 60, 46,31. I don't like the 46 degree cut for the seat. I had several valves that leaked after lapping and then running the engine. When checking using compressed air at 80 psi, I tried lightly re cutting and lapping with the Neway cutters but I ended up using an older 45 degree seat cutter that I had to finally get them to seal. I don't think the T combustion chamber pressure gets high enough or maybe its the spring pressure is too low to seat a 45 valve on a 46 degree seat. The other two angles are used in the end to determine where the seating area contacts the valve and control the width of the seating area so I don't think those angles matter as much. IMHO I would use the 45 degree cutter. I really like the Neway set up but wish it didn't cost $200 to get a 45 degree cutter head.