'51 8N valve job

Hey guys, I have replaced the valve seats in my '51 8N and I need to cut the seat faces and I was going to use a Neway carbide cutter with a 0.342 diameter pilot. I was wondering if only cutting a 45 degree seat face angle is sufficient or is it necessary to cut three angles at 30, 45 and 60 degrees. I will be doing this manually and have no way to grind three angles on the valves. Any input will be appreciated. Thanks, Matthew.
 
While there's certainly nothing WRONG with a 3 (or 5) angle valve job, with the low displacement per cylinder, slow turning "N" engine I think you'd have to split a gnat's eyelash to see a measurable HP gain vs. the simple valvejob it left the factory with, IMHO.
 
get it done properly...as how do u expect to get the seat on the valve in the correct position like that. there is also a seat width spec. also. and there is an interferance angle also... seats 44 degree's and valves 45 degree's to give the valves a good and faster seating. gotta use 3 stones. and you no not grind three angles on the valves, its the seats that require that.
 
Thanks for the input guys. Unfortunately there is no competent machine shop near me to get this done by a professional so I'm going it alone.
The I&T FO-4 manual covers valve seats on page 28 paragraph 26. It calls for grinding, or cutting, the seat faces to 45 degrees, seat face
width not to exceed 0.125 inch. YT service manual page 20 shows same procedure and includes minimum seat face width spec of 0.062 inch. Both
service manuals call for 30 and 60 degree cuts only if seat face width needs to be reduced, assuming I comprehended both manuals correctly.
This afternoon I ordered a Neway seat cutter number CU234 with 30 and 45 degree cutters. After cutting my plan is to lap each valve then give
them the bubble test I saw on a video. Here is the link.https://www.youtube.com/watch?v=o_a-qowOnHo
 
The FO-4 covered an alternative method for seat removal using an arc welder. I did something similar with a smith torch, cutting tip number 00. Dry ice and two sockets for the new seat install.
 
Matt, You do not need to lap the valves if you are using Neway cutters. When you use stones you need to lap the valves.
 
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Figure FO-33 in the I&T manual illustrates welding 3 small beads onto valve seats, I heated them orange in 3 spots and they came out easily by gentle prying with a flat screwdriver
.
 
you never lap valves when using stones. that is an old obsolete way they used to do it back then. that is the whole idea of the interferance angle.
 
Lap, don't lap, who knows. I'll use my not so popular and unorthodox methods to get these new valves to seal tight. They must each pass the bubble test with a blow gun and soapy water. I'd like to see this tractor idle at 450 RPM. Takes good valve sealing to achieve that low of an idle. Be neat to watch the vacuum gauge after this valve job.......Thankful there is no computer on an 8N. :D
 
6 years ago An engine shop installed new seats and ground them with a single angle, Then I hand lapped them and it is still running great. These are NOT racing engines.
 
(quoted from post at 23:06:51 10/18/16) 6 years ago An engine shop installed new seats and ground them with a single angle, Then I hand lapped them and it is still running great. These are NOT racing engines.
hank you R Geiger, that's good to hear.
 

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