Cutting piston bowls

mfsuper90

mfsuper90

300ft is all I need
Getting ready to do a Reenterant delete to an engine I’m playing with.

The piston im working on has an offset bowl with a deep lip. My plan was to cut the lip straight down to the bottom radius of the bowl. Going to chuck it up in a four jaw chuck and center it to the offset bowl then cut the lip off. I’d love to post pictures, but photobucket screwed me and I haven’t taken the time to figure anything else out.

I know bowl geometry is a complicated design, so I’m not looking to totally redesign it. I just want to open the bowl up to keep from burning the lip off the piston when we run advanced timing.

Application is a 1006 perkins running a “Farm stock” class
 
Well I finished them

34285aedb35812030870d81073c88c40.jpg


Before and after.
Before the bowl ID was 1.9, now it is 2.45”
Went from 45cc bowl to 60cc. Should put compression at 14.5:1. I think that’ll work fine for what we are doing
 
mfsuper90 said:
Well I finished them

34285aedb35812030870d81073c88c40.jpg


Before and after.
Before the bowl ID was 1.9, now it is 2.45”
Went from 45cc bowl to 60cc. Should put compression at 14.5:1. I think that’ll work fine for what we are doing
Click to expand...



Nice work!


Sent from my iPhone using Tapatalk Pro
 
Interesting side note, just torqued the head down. Specs are 80ft lbs then plus 180 degrees if it’s a medium length bolt (different lengths get different degrees). After running them, I set my torque wrench to 150ft lb, and the bolt I tested didn’t even budge.

I’m not a big guy, I had to have a 3ft cheater pipe to get them torqued. That’s a lot of torque on a 1/2” bolt
 
TheBac said:
You did good. Thats how shops cut Dmax pistons, for the same reasons you did. What size radius did you put on the edge?
Click to expand...

I gave it the eye ball radius :lolly:

I’m no machinist by any means, but I’m slowly learning. The grinder I use has no degree marks so cut them by eye with the regular tool I was using. Then I cleaned them up with some rough sandpaper and finished them with some rough scotch brite (red pads?). I couldn’t get my tool to give me the surface finish I wanted, but it did the job. Need to upgrade my tooling
 
I like it. :) I believe when Merchant cut mine, his machinist used a .25" radius. Yours look close to that.
I figured it lowered my comp ratio around .5 by doing so, too.
 
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