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Piston to bore clearance tsm typo?

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First_Gear View Drop Down
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    Posted: Jan/26/2021 at 11:57am
Ok so I have my old 232 partly taken apart. I have the new head in the mail. I want to replace the rings as well since increased compression in the head can cause blow by around the rings or so I've read. 

Anywho the tsm states "piston to bore clearance specification is 0.0003 to 0.0009" is this a typo?? This is an insanely tight clearance. I would think 0.003- 0.009 makes more sense.

It does not specify where in the bore you are supposed to take this measurement. Then it says cylinder taper must not exceed 0.003". This does not make any sense if the piston to bore clearance is a tighter tolerance.. I'm assuming, hoping it's a typo. I'm not even sure I can accurately measure 0.0003"

Thoughts? Does anyone have a later tsm? This is a 66 and I'm reading the specs for the 232.

Edit: I now see it says to measure this 2 5/16" below the top of the deck. It still seems insanely tight. Just honing it could change it by several tenths.


Edited by First_Gear - Jan/26/2021 at 12:06pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 58American! Quote  Post ReplyReply Direct Link To This Post Posted: Jan/26/2021 at 4:18pm
That has to be a typo. Standard would be right in the range you mention, although I think better is 0.003 to 0.006. 0.009 is starting to get a bit loose.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote First_Gear Quote  Post ReplyReply Direct Link To This Post Posted: Jan/26/2021 at 7:33pm
I did some more research. I don't think it's a typo! There's no way a used engine is going to meet those specs so I'm just going to press on with my ring job and not worry about it. If I were doing a full rebuild I would bore it out and buy oversized pistons but not for a simple ring and head job.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Cricket Quote  Post ReplyReply Direct Link To This Post Posted: Jan/26/2021 at 7:41pm
Originally posted by First_Gear First_Gear wrote:

I did some more research. I don't think it's a typo! There's no way a used engine is going to meet those specs so I'm just going to press on with my ring job and not worry about it. If I were doing a full rebuild I would bore it out and buy oversized pistons but not for a simple ring and head job.

Now you Don’t think it is a typo? I’m Pretty sure it IS a typo, .0003-.0009 is ridiculous tight for anything, especially an engine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote First_Gear Quote  Post ReplyReply Direct Link To This Post Posted: Jan/26/2021 at 9:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jan/26/2021 at 9:40pm
That's the Piston to Pin clearance put in the wrong spot.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote First_Gear Quote  Post ReplyReply Direct Link To This Post Posted: Jan/26/2021 at 9:57pm
Originally posted by Trader Trader wrote:

That's the Piston to Pin clearance put in the wrong spot.

JEEZ! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote First_Gear Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2021 at 12:16am
https://theamcforum.com/forum/uploads/1736/232_Engine_Manual.pdf

And page 23 here? It just seems crazy there would be that many typos but the ring clearance does seem hard to believe.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 58American! Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2021 at 1:15pm
You could maybe go that tight for cast iron pistons in a cast iron block, but no way for aluminum pistons in a cast iron block.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote First_Gear Quote  Post ReplyReply Direct Link To This Post Posted: Jan/27/2021 at 10:30pm
When I get the pistons out I will measure the bore diameter and the piston and post my findings.. Of course this engine had been rebuilt in the past plus some wear and my tools aren't accurate to the nearest 0.0001 but maybe it will shed some light on this. Every source I have checked on google seems to be around 0.0009 to 0.0017 with some minor variations.


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