David Ashcroft
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Is a flat band on headbuttons necessary. What are your thoughts .
head button
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bermudadude
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not literally. it only has to match the piston so it can [squish]
thats the short answer
thats the short answer
David Ashcroft
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Thanks Shawn, I am getting a Button made and I was going to have a 0.70thou 1.78mm flat outer band but ,rather I will have a 2 or 3 degree taper all the way to the edge.
Thanks
Thanks
bermudadude
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well if u must have a taper ,makes for less critical setup/tuning, then 1/2 degree.but the outer edge should be flat at least 1mm it will trap unburnt fuel which prevents seizure. esp if it going to be the whole distance. 2-3 is waaaayy too much. unless its only the middle 1-2mm,but with all those calculations it starts getting complicated. then u gotta close the bubble down to get c/r back up.. lots a numbers lol
David Ashcroft
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My stock 80 button has about a 1mm outer flatband.Another good source just expained to me that squish band size should be 65%-75% of the bore volume ,and don't have a outer flat band, but angle band right to the edge.
Jim Allen
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David,
65% to 75% of the bores area is a large amount of squish band area & may cause the engine to go into detonation, rather than help prevent it. 45% to 50% would be considered ideal. Even toroidal type combustion chambers would not have more than 50% squish band area.
JA
65% to 75% of the bores area is a large amount of squish band area & may cause the engine to go into detonation, rather than help prevent it. 45% to 50% would be considered ideal. Even toroidal type combustion chambers would not have more than 50% squish band area.
JA
David Ashcroft
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I have read a number of opinions about squish widths and they vary from 45% upto 75% of the bore volume. At the end of the day it's just cut and try to suit your application and see what happens.I am just getting my buttons cut according to my engine program .I know my new brass button is now .68cc .244"band width @2deg opposed to Stock .72cc .255" width.
Adam Blevins
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This is a topic where its definitely not a one size fits all so to speak...
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