How Much are you Milling your heads?

#1
I made up a tool like KustomKartKids for turning/milling a flathead Briggs cylinder head in the lathe, and I am wondering: how much material are you taking off when you are milling your heads? I don't mean for a racing application, just a general modded 5hp Briggs.

I ran this head for a trial run and I ended up taking .045" off.
ImageUploadedByTapatalk1426756881.121432.jpg
 
#2
Hi Clay,

This is from the "Awesome Guide to Modding Briggs thread:

"Get a Raptor BluePrinted head for $30 on eBay, and if you get a milled head, or one milled yourself, don't ever buy one or get one milled over .030. Any more than that, and again, flow starts to decrease. You won't notice any more speed from this, but more torque and power in the middle end."
 

CarPlayLB

Well-Known Member
#6
I use a piece of glass and wet dry sandpaper. Takes some time, no where near as perfect as yours Clay, but it gets the job done!
 
#7
I use a marble tile with a round stick on 80 grit disc on it and rub it in different directions . This works unreal I've done a Honda head and a raptor head and there flat and don't leak . Here's a pic of the Honda head , looks like it came off a milling. Machine .
 
#9
I took off .030 and it seems to run much better. Unleashed some torque. I used a bridgeport mill and power feed. The cutter was a 1/2 inch carbide endmill. It left some swirls, but they were easy to stone off.
 
#10
I always used to do it by hand on a nice flat surface with sandpaper, but once I saw how KustomKartKid did his on the lathe I figured that would be a quick and easy way to do it. I checked run out on the head and I only got .001" difference all the way around. I thought about using the mill but thought setup might take longer depending on how true the top of the head and the gasket surface would be to each other. Especially considering wear.
 
#11
I wish there was someone near me to mill flat heads. Nobody wants to take the time...:confused::surrender::censure:
That's the sad thing, something like this doesn't take much time, but a machine shop doesn't make enough from it to be worth while for them. Or at least that's what I always ran into before I was able to do it myself.
 
#12
Wow! I can't believe it was only out a thou! It took me a while to tap it around to get it that true. I'll have to try that out after the guy that runs the lathe leaves for the night.
 
#13
Looks good Clay...I was going to ask how much run out was in it before you started. I was hoping it didn't take .045 just to clean up.. HA ! Various factors can contribute to run out like the spark plug hole not being tapped perfectly perpendicular , or the plug gasket surface is uneven or the end of the tool you made not faced off square...or the head is just warped. Good to know it was only out .001 that's nothing.
The other problem is with the offset plug hole you have all that unbalanced mass spinning around you can't really spin it as fast as you would like to get a good fininsh unless you want the lathe to start walking across the floor. I originally made the tool way back when to do moped heads that were very small in diameter and had a centered plug...you could spin those up no problem.
You did a great job with that, the finish looks perfect. :thumbsup:
 
#15
Pretty sure you need a lathe with at least a 10 " swing to face off a small block Tecumseh or Briggs head. I think the H35 head just barely cleared on my 10" South Bend.
 
#18
Thanks for offering Phil and thanks for saving me the shipping Gerry...


Sent from my Texas Instruments Speak and Spell...[emoji2]
that doesn't mean i can't do it! let me try out a tecumseh head. if i can
mount it and get it trued i'll let you know. otherwise you are forcing
me to buy a milling machine......
 
#20
Thanks Gerry, I started out with a tool with a .002" nose radius and it chattered where the head is further from the chuck, but I ground a brazed on carbide tool to a point and dropped my feed right down and it go rid of any chatter.

I too was surprised on how little it ran out, but as was mentioned, how straight or wore out the plug hole is will determine the run out.

I did this head at work on a lathe with a 18" swing but 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. ImageUploadedByTapatalk1426900228.056611.jpg
 
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