a boring question...
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Senior User
Joined: Nov 2005
Posts: 236
Likes: 1
From: Texas
a boring question...
Ok, just bought a shortblock thats "supposed" to be rebuilt. However it still has the stock pistons in it 
. So my question is how far can the 7.3l be bored out and still use the stock size pistons 
?
. So my question is how far can the 7.3l be bored out and still use the stock size pistons ?
Posting Guru
Joined: Feb 2004
Posts: 2,365
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From: IOWA
I can't answer your question, but I thought it was going to be an "uninteresting" one!
Are you going for high performance? If it has stock pistons, what was rebuilt then? or just new parts put to it, like rods?
Are you going for high performance? If it has stock pistons, what was rebuilt then? or just new parts put to it, like rods?
Hotshot
Joined: Jan 2002
Posts: 17,988
Likes: 207
From: La La Land
For proper piston-to-wall clearances, it can have NO over-bore if using stock diameter pistons.
There are many reports of the cross-hatch hone marks being still evident at teardown after hundreds of thousands of miles, so it's conceivable that it didn't require an over-bore to rebuild it.
However, that said, to maintain the tight tolerances that prevent piston "slap" I would like to think they used new "standard" pistons.
If I were doing it, I'd use the smallest oversize piston and power-hone it to size, i.e., not use a boring bar at all unless taper or ledge made it absolutely necessary. Sunnen makes a nice machine to do just that, and the stones aren't THAT expensive.
Pop
There are many reports of the cross-hatch hone marks being still evident at teardown after hundreds of thousands of miles, so it's conceivable that it didn't require an over-bore to rebuild it.
However, that said, to maintain the tight tolerances that prevent piston "slap" I would like to think they used new "standard" pistons.
If I were doing it, I'd use the smallest oversize piston and power-hone it to size, i.e., not use a boring bar at all unless taper or ledge made it absolutely necessary. Sunnen makes a nice machine to do just that, and the stones aren't THAT expensive.
Pop
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Senior User
Joined: Nov 2005
Posts: 236
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From: Texas
No build sheet because i just bought it off ebay, only spent a couple hundred for it, two heads and an assortment of other engine parts. So im not sure that it actually was bored out, just the cross hatch marks and the fact it was supposed to be rebuilt made me think that it was bored. The pistons are the originals i know because they still have soot stains from combustion.
I guess im going to have to find a good machine shop around and have the wall thickness checked to make sure that its not bored. but my plans are to do a performance build with it so ill be taking it all apart anyway for fire ring-ing and aftermarket rods and pistons.
I guess im going to have to find a good machine shop around and have the wall thickness checked to make sure that its not bored. but my plans are to do a performance build with it so ill be taking it all apart anyway for fire ring-ing and aftermarket rods and pistons.
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Lead Driver
Joined: Jan 2007
Posts: 6,708
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From: Kiowa CO
No build sheet because i just bought it off ebay, only spent a couple hundred for it, two heads and an assortment of other engine parts. So im not sure that it actually was bored out, just the cross hatch marks and the fact it was supposed to be rebuilt made me think that it was bored. The pistons are the originals i know because they still have soot stains from combustion.
I guess im going to have to find a good machine shop around and have the wall thickness checked to make sure that its not bored. but my plans are to do a performance build with it so ill be taking it all apart anyway for fire ring-ing and aftermarket rods and pistons.
I guess im going to have to find a good machine shop around and have the wall thickness checked to make sure that its not bored. but my plans are to do a performance build with it so ill be taking it all apart anyway for fire ring-ing and aftermarket rods and pistons.
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Thread Starter
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Senior User
Joined: Nov 2005
Posts: 236
Likes: 1
From: Texas
Ya, i won't worry about boring it unless its recomended to do so, at most id do a honing technique like pop suggested. But does anyone know of a good machine shop, thats worked with diesels before, in the dallas/ft. worth area?