372 with 268xp piston help

[MotherGoose]

hello im new here. I just acquired a 268xp piston to put in my 372xp. I measured my squish as it sits with factory base gasket. I got 42 to 46ish so my question is how much of do I have turned on the 268 piston to get the squish to 20. Also how wide of a pop up. I hope I made that clear. Any help would be appreciated thanks

 

[Stump Shot]

Hello and Welcome to OPE.
It's pretty much about measuring and reference points. Measure your 372 piston from the top of the pin hole to the top of the dome and the same for the 268 piston, then subtract. This is your difference to cut off to be standard. So if squish is at lets say .044" then take .024" less to be at .020" final squish. Measure your squish band width to see how wide to cut, this should be just a little bit wider, roughly around 10mm.

Here I used the reference point of the top of the ring land to get my final measurement while cutting this 272 piston.

 

[MotherGoose]

Ok thanks I think I came up with the number. I see you have a lathe. Is this something you do for work?

 

[Stump Shot]

Ok thanks I think I came up with the number. I see you have a lathe. Is this something you do for work?

Glad you got it figured and no, I haven't turned Pro yet.

 

[MotherGoose]

Ok cool. I need to find a machinest then. Thanks for your help hoping this is going to satisfy my crave for more power. Not ready to do any port work yet

 

[Stump Shot]

Plenty of them around here for hire. @huskihl

 

[huskihl]

I could turn a pop up. Not sure of the final port timing numbers though. I suppose if you sent the cylinder also I could tweak the ports to where it would run

 

[MotherGoose]

That would be great. What’s the cost of having the piston turned

 

[huskihl]

Sending you a pm

 

[cgraham1]

I’ve had @Mastermind and @blsnelling do machine work for me in the past. It seems that lots of other guys around here can do it, as well.

 

[MotherGoose]

Cool thanks but I’ve got huskihl helping me out

 

[Dub11]

FFP FTW!

 

[drf256]

Kevin will get you set up.

What I can’t figure is your numbers. If your squish sits at .042, there’s nothing you can take off the piston to tighten it up. Unless you are stating that the stock 372 sits at .042, and the 268 piston is taller.

 

[Mastermind]

Never found this mod to be worth the hassle.

 

[David Young]

The 268 piston is 1mm taller approximately 40 thou. The ex and transfers will stay the same as stock but you will end up with long intake. Like 82-83

 

[huskihl]

The 268 piston is 1mm taller approximately 40 thou. The ex and transfers will stay the same as stock but you will end up with long intake. Like 82-83

That's what the math says. Intake should open 2-2.5mm earlier

 

[Marshy]

Never found this mod to be worth the hassle.

Maybe you were using baking soda instead of baking powder?... j/k. Never heard of this mod before. Sounds interesting. Note to self, I need a lathe.

 

[MotherGoose]

I was hoping this 268 piston would hold me over for a little while until I’ve finished some other projects and can afford getting the saw ported and done up right. I just figured I can always pull the piston out and have it ported later

 

[Mastermind]

I was hoping this 268 piston would hold me over for a little while until I’ve finished some other projects and can afford getting the saw ported and done up right. I just figured I can always pull the piston out and have it ported later

It works fine for some guys.....but the way I build that needs as much case compression as possible. The full skirted piston really helps move the transfers.

 

[old guy]

Never found this mod to be worth the hassle.

Oh,I love mine, tons of torque.