All Small Six Winter Project: Better breathing with a large log

[awasson]

I think the guy in the video said he used 50* a lot. But not on a six

I think he was talking about his seat angle preference when he said 50°. I think ours will be 45° seat angle. He seems to work on really exotic high performance stuff.

 

[clochard68]

@Engine Fan : What tool did you for the backcut and the radius besides the drill press? File or stone?

Also here is an article from Joe Mondello who also talks about backcut and breaking the edge of the intake valves:
"Reface valves 45 º undercut 30 º the same width of your 45 º primary seat angle. On the upper edge of the 45 º next to the margin set your valve re-facer to 50 º and break the edge .005” to .007” wide."

realoldspower.com-Great article by Joe Mondello

Lots of great info in this article written by Joe, plenty of his "hardcore" racing specs. Rocketing the 455 Oldsmobile Engine into the Future By Joe M

www.tapatalk.com

 

[Engine Fan]

@Engine Fan : What tool did you for the backcut and the radius besides the drill press? File or stone?

Also here is an article from Joe Mondello who also talks about backcut and breaking the edge of the intake valves:
"Reface valves 45 º undercut 30 º the same width of your 45 º primary seat angle. On the upper edge of the 45 º next to the margin set your valve re-facer to 50 º and break the edge .005” to .007” wide."

realoldspower.com-Great article by Joe Mondello

Lots of great info in this article written by Joe, plenty of his "hardcore" racing specs. Rocketing the 455 Oldsmobile Engine into the Future By Joe M

www.tapatalk.com

File and emery cloth was used.
And yes break the edge of the margin next to the seat, but leave the combustion chamber side of the margin sharp

 

[clochard68]

break the edge of the margin next to the seat, but leave the combustion chamber side of the margin sharp

Thanks, good advice about leaving the chamber side edge sharp, I was wondering about that...

Also your valves look so precisely cut, I thought you machined it with a professional tool... really a job well done

 

[awasson]

Did mine for a 300 on the drill press. Lapped the seats after(gray line). Has always been part of a build for me.
No need to backcut the exhaust(one way flow)
Just radius the margin on the exhaust
Keep the intake margin sharp.

This is exactly what I was proposing to do with my drill press and a file. I figure I can build a jig at 30 degrees for the file so that I can get that back cut right and only back cut the intakes and only radius the front of the exhaust margins.

That info from the article @clochard68 posted fills in some knowledge gaps too.

I’ll see what the shop wants to charge for doing that. If it’s an unreasonable amount, I can still do it myself.