225 to 235

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elvaliant66

elvaliant66

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Have a 225 the motor was supposedly rebuilt and now is a 235 c.i. . How do I calculate how much they bored out?thanks in advance !
 
Pretty shitty quality in that pic but all I see is C 225 5 "05" not sure on the last 2 numbers stamping gets cut off and lighting is bad in the pic
 
A 225 is 3.40 x 4.125stroke, for a 224.7cid total

To make 235 cid the bore would need to be 3.477. this is .077 oversize.
If one assumes a piston could be found at plus .080, the actual bore would be 3.48, and the final cid would be 235.4.
Whether or not the block would accept 80 over I cannot say; this is just the math.
 
They rebuilt a Chevy....
original%20engines%203.jpg
 
235 / 6 = 39.1666666

39.1666666 / 4.125 = 9.4949494949

9.49494949 / pi = 3.02233629

sqrt 3.02233629 = 1.73848678

1.73848678 * 2 = 3.47697" bore
 
AJ/FormS said:
A 225 is 3.40 x 4.125stroke, for a 224.7cid total

To make 235 cid the bore would need to be 3.477. this is .077 oversize.
If one assumes a piston could be found at plus .080, the actual bore would be 3.48, and the final cid would be 235.4.
Whether or not the block would accept 80 over I cannot say; this is just the math.
Click to expand...

So I'm pretty sure it's probably b/s that it has been rebuilt . The only way to find out is by removing the head? Gonna do a comp test see where it's at.
 
.080 over pistons were readily available at one time. So it is possible.
PS: A slant can usually be bored .100 with no problems. Some have gone even bigger.
 
I have a magazine form the 60s that says they bored a slant six .130 over, so .080 would not be out of the question. There is a lot of metal between the cylinder wall and water jackets, which is also one of the reasons they last so long. Mine is bored .040 over which works out to just under 230 cid. I plan to go bigger next rebuild.

Bore 3.40 + .040 = 3.44 formula is pi x radius squared x stroke x no. cyls

so 1.72 x 1.72 x 3.14 x 4.125 x 6 = 229.9; or in your case with a bored of 3.48; 1.74 x1.74 x 3.14 x 4.125 x 6 = 235.28 cid
 
Rock Auto still lists the .080 piston for the slant six. Sealed Power 244NP at $23.79 ea.
However, they do not have ,080 rings listed. That could be a problem.
 
Charrlie_S said:
Rock Auto still lists the .080 piston for the slant six. Sealed Power 244NP at $23.79 ea.
However, they do not have ,080 rings listed. That could be a problem.
Click to expand...

Seal power can make a set no problem, about 120 shipped
 
You should be able to get rings by type and size.

You might have to look for another make's piston with a different oversize....
 
If memory serves me correctly (no guarantees ) I bored one of my /6's .060 over, and it came to 232 Cu In !!
 
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