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Old 08-20-2018, 10:04 PM   #1
Scooby Newbie
Member#: 490311
Join Date: Aug 2018
Chapter/Region: South East
Location: Florida
2006 WRX STI
World Rally Blue

Default Oversized Valve Guides?

Im rebuilding my heads, and i was looking into valve guides, i understand they come in different bronze materials, but GSC Power Division offers them in +.001 & +.003 option. I am not quite sure the application purposes or what the pros and cons of oversized valve guides would be.
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Old 08-21-2018, 09:29 PM   #2
Scooby Guru
Member#: 32669
Join Date: Feb 2003
Chapter/Region: SCIC
Location: Woodland Hills
2007 2.34LR, EFR7670
LINK G4+ hybrid STi


I honestly don't know enough about oversize valve guides to talk intelligently about the subject. I also know if you don't have the proper tools and knowledge to install them which most people don't, it really doesn't matter to the end user. The shop that rebuilds your head's will replace the valve guides if necessary and size them according. The clearance value is more important for the end user than whether or not it was oversized by .001 or .003
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Old 08-21-2018, 10:34 PM   #3
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Join Date: Dec 2013

Sometimes when a guide is removed, some parent material comes with it. In that case, a standard guide would not have enough press fit so oversizes are needed.
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Old 08-22-2018, 08:45 AM   #4
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Join Date: Sep 2004
Chapter/Region: NESIC
Location: USA
Leh Keen Approved
'68 Volvo Amazon


Correct. Oversized guides are on the OD for when a press fit cannot be achieved due to oversized guide bores in the head. As long as there is no damage (when removing the old guides) and you head is in good condition the STD sized guides should work fine.
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