hey guys,
this guy on ebay says he’s selling USDM ITR .25 overbore pistons…
is there an “mark” that i’m missing here?
Originally posted by gen2ls/vtec
has anyone calculated the displacement difference these overbore pistons make? I dont know the equation, but if anyone knows it or has a link to it please post- thanks guys!!
Asuming Area=r²(pi), and Volume=(area)(stroke):
4.05²3.1416 = 51.530094
4.075²3.1416 = 52.1682315
52.1682315 - 51.530094 = 0.6381375
0.6381375*8.14 = 5.19443925
So the difference between standard bore pistons and 25 over bore pistons in a B17A are only ~5cc’s, thus negligible. People use overbore pistons because eliminating any harsh irregularities in the cylinder walls after tear-down that would require a bore and hone would make overbore pistons necessary to compensate for the boring done.
Tony, here is what an oversized USDM ITR piston should look like. Part # is on the box. HTH
so is it safe to say that using overbore pistons stricly b/c you want a larger displacement is not the wisest of choices? Now using them b/c you’re block needs to be repaired I can see, but just to get another 20-30 cc of dispacement it doesn’t seem like the best investment in either time or money. Anyone disagree?
Originally posted by 92GS-R
[B]hey guys,
this guy on ebay says he’s selling USDM ITR .25 overbore pistons…
is there an “mark” that i’m missing here?
[/B]
so you can kind of see where it looks like it used to say “25”
ARCHIVETHIS
Yeah, I think his are oversized. He needs a digicam with “macro” mode 
Originally posted by gen2ls/vtec
so is it safe to say that using overbore pistons stricly b/c you want a larger displacement is not the wisest of choices?
Yes it’s safe to say.
Now using them b/c you’re block needs to be repaired I can see, but just to get another 20-30 cc of dispacement it doesn’t seem like the best investment in either time or money. Anyone disagree?
With such little difference in displacement from standard to overbore, yes you are right. However, changing actual piston types in an effort to increase CR is a valued investment.
Alright… I think I’m going to go with the PR3 (1st gen b16a) pistons. Is a good idea to upgrade my rods? or get them polished and shotpeened? ARP rod bolts?
thanks guys… 
…
sigh I could have bought a nice Marshall Tube Amp and a Gibson Les Paul with all this money 
hehe 
Originally posted by 92GS-R
[B]
sigh I could have bought a nice Marshall Tube Amp and a Gibson Les Paul with all this money 
hehe 
[/B]
Ah well…much better investment IMO.
Originally posted by B17A
Ah well…much better investment IMO.
not IMO… but oh well… 
Rods
Now that that my pistons questions were answered could someone school me about rods? What does shotpeened means? And if you upgrade the pistons do you really need to do this? Someone please tell me
Originally posted by Ive
[B]Asuming Area=r²(pi), and Volume=(area)(stroke):
4.05²3.1416 = 51.530094
4.075²3.1416 = 52.1682315
52.1682315 - 51.530094 = 0.6381375
0.6381375*8.14 = 5.19443925
[/B]
Dammit! What is that 8.14? It’s driving me nuts!
Though it’s been established already, the reason Honda makes OEM .25mm overbore pistons is for rebuild purposes.
BTW I didn’t know that PR3 pistons are only $40. Compared to $100 for the ITRs that’s pretty good.
:read:
Originally posted by GSpeedR
[B]
Dammit! What is that 8.14? It’s driving me nuts![/B]
Stroke length of the B17A, in cm.
I am so dumb…:sick: For some reason I kept reading it incorrectly.
Thanks
Re: Rods
Originally posted by JTeg
Now that that my pistons questions were answered could someone school me about rods? What does shotpeened means? And if you upgrade the pistons do you really need to do this? Someone please tell me
shot peening is a process that in theory strengthens the metal and prevents stress risers. basically by “dimpling” a metal surface this creates a zone of cold compressed metal below the dimple. As the metal in this zone wants to return the overlying metal back to it’s orginal fiber length, it creates a cold compression zone which by the laws of physics makes starting and propagating of cracks less likely. Also as I’ve heard it reduces stress risers…
kind of a complicated concept…
Makes much more sense but where would I do something like this? A speed shop would do this?
I believe it’s…
roughly ~40cc more for a set of 25 over’s…I’ll double check and get back to you on that.
-Jeff C.
Originally posted by JTeg
Makes much more sense but where would I do something like this? A speed shop would do this?
most machine shops that do engine work can do it for you. best to start calling around to bunch of places to get price quotes, and make sure you ask those in your area for any recommendations on trusted shops that do good work.
Thanks Tony