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Boring out a B18 for B20 pistons? 444-544

posted by RallyVolvo on Wed Apr 18 04:42 CST 2007
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last visit: Sat Jun 9 08:17 CST 2007

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I'm planning on boring out a B18 to install a set of standard B20 pistons that I've had lying around for a while. As far as I know this shouldn't be a problem, but are there any issues with this mod that I'm not thinking of?

-Nick

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ANSWER Boring out a B18 for B20 pistons? 444-544

posted by 122 and 940 and too many on Wed Apr 18 05:59 CST 2007
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last visit: Mon Apr 25 13:12 CST 2011

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If its an early B18 block its possible there isn't enough meat and the metal twixt piston and water jacket gets excessively thin. Normally OK though.

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Boring out a B18 for B20 pistons? 444-544

posted by Phil S. on Wed Apr 18 07:09 CST 2007
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last visit: Fri Oct 24 13:18 CST 2014

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They usually bore that large just fine unless 1) there's a lot of core shift (the original bores are off-center relative to the casting, 2) there's a casting flaw (air bubble in the metal) or 3) lots of corrosion in the water jackets.

What you can do is have the block sonic tested to see how much metal currently surrounds the bores.

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ANSWER Boring out a B18 for B20 pistons? 444-544

posted by JohnMc on Wed Apr 18 04:51 CST 2007
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last visit: Thu Oct 23 07:42 CST 2014

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Talking a skeptical machine shop into doing it. Finding a B20 head to use on it afterwards. That's about it.
--
'63 PV544 rat rod, '93 Classic 245 + turbo

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Boring out a B18 for B20 pistons? 444-544

posted by RallyVolvo on Wed Apr 18 06:39 CST 2007
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last visit: Sat Jun 9 08:17 CST 2007

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"Talking a skeptical machine shop into doing it."

Hah. Nice...
I have at least 6 B18 blocks to choose from, and probably 9 or 10 B20 heads. I've lost count recently... All should be good then. Thanks. I've also noticed some really early B18s don't have the mounts for the cast aluminum bell housing brace. Why am I not using one of the B20 blocks I have? They're all worn and need to be overbored. Since I'm trying to do this on the cheap and already have a set of std. size pistons, it seemed the way to go. Speaking of which, I have 2 extra standard B20 Mahle pistons if anyone is interested...

-Nick

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Boring out a B18 for B20 pistons? 444-544

posted by someone claiming to be VainGlory Racing on Thu Apr 19 07:09 CST 2007 [RELATED]

Any of the B18 blocks have the boss on the right hand side for mounting the AC pump? If so I would be interested in buying them from you.

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