How Much are you Milling your heads?

#21
.... I just chucked it up on my lathe with 11" swing and it clears the ways with some room. I think it may be able to be done on a 10" swing but likely no smaller.
Noted and corrected... that's good to know. When I looked at the picture the plug hole offset looks like it was more than the Tecumseh and I thought I remember that being close on the 10" lathe. Must be an optical illusion...doesn't look like that Briggs head would ever swing in a 10" lathe.

What model motor is that head from...that lip around the one edge looks odd to me ? Maybe I just never noticed it before. Can you get away with machining just the head gasket portion or will that lip contact something. It must seem like it takes forever when your feeding slow across that section...tick....tick....tick....tick.
I would machine it off too like you did...well...just because it would bug me if I didn't. :rolleyes:
 
#22
This head is from a newer flathead 5hp Briggs. I'm not for sure, but I don't remember that lip on the older engines?

I think I had to machine that edge as well, but I'd have to check again, but like you said it probably would've bugged me if I left it.
 
#23
Should also note that sometimes the travel of the cross feed screw is the limiting factor. You may be able to rotate a the piece in a 10" lathe, but may not be able to face it with one continuous cut. That is when a bigger lathe comes in handy.
 
#24
Should also note that sometimes the travel of the cross feed screw is the limiting factor. You may be able to rotate a the piece in a 10" lathe, but may not be able to face it with one continuous cut. That is when a bigger lathe comes in handy.
That's a good point. This post made me check it out, and I don't have much travel left on my cross slide, on a 11" swing.
 
#26
Couldn't you chuck your adapter in a 4 jaw chuck and try to better center the head so it isn't so off balance?
Yep...it would take some trial and error to find the sweet spot but then you could put some witness marks on the chuck so you could always come back to it later.
 
#28
There is an alternative to milling your 5hp flathead. Find a 4hp head. They have less volume than the standard 5hp head, thus raising your compression. You can identify a 4hp head because it has '10' cast into the front left corner between the fins. A normal 5hp head has a '13'. I have seen briggs I/C motors that came from the factory with this change. The bad news; 4hp heads aren't easy to find.
 

Beal

New Member
#30
I had read something saying not to use the 4hp heads. But now I don't remember the reason. Something about the valves maybe?

But hey if it works that's great
 
#33
I did my 3.5hp .015" using a tile and sandpaper. I don't like to go too far. Every time I take the head off to clean I take another .005" to clean it up. I used to work as a machinist. If doing it at work, I would probably do it on the CNC lathe and just run a quick program to face it; with a higher rpm slow feed/high speed skim cut.

Since this is an interrupted cut you guys should use coated inserts with the right geometry for aluminum. Do the roughing with a .016 radius and skim cut it with a .002 or .004 with slow feed at higher rpm.
 
#34
There is an alternative to milling your 5hp flathead. Find a 4hp head. They have less volume than the standard 5hp head, thus raising your compression. You can identify a 4hp head because it has '10' cast into the front left corner between the fins. A normal 5hp head has a '13'. I have seen briggs I/C motors that came from the factory with this change. The bad news; 4hp heads aren't easy to find.
Yes it gives ypu alot more compression but you actually can go to far. It hurts so much flow that it kinda offsets the compression, so you would get good low end but weak top end.
 

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