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post #1 of 5 (permalink) Old 05-05-2012, 11:57 AM Thread Starter
 
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1967 gto 400

Can anyone provide any information about boring out a 400 GTO engine. im wanting to bore it out for increased horsepower. Is there any way i can bore it out to make a 455 pontiac. Any help would be appreciated

thanks
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post #2 of 5 (permalink) Old 05-05-2012, 12:07 PM
 
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with a stroker crank and forged rotating assembly it can be a 462+ depending on the bore and stroke.

here is the long stroke kit

Pontiac 400 Stroker Kit 4.500 x 400 block | eBay

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post #3 of 5 (permalink) Old 05-06-2012, 12:08 AM
 
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Just an over bore will do very little for performance. It's all about getting air in and air out. Heads and cam is where power come from. If all else is equal a .030 or .060 overbore will not produce anything extra to speak of. Work on them heads and select the right cam if you want a kick.

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post #4 of 5 (permalink) Old 05-06-2012, 06:08 PM
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Agreed. On overbore is used to overhaul an engine, not to produce power. These engines can be bored safely .060" oversize, after that, you'd need to sleeve it. The rule of thumb is to bore as little as possible......020. .030, .040, etc. You can overhaul an engine several times instead of once, this way. Easy to increase the power and displacement with a stroker crank kit and a well matched camshaft and set of heads. Check out Bear's 461 build on this forum.
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post #5 of 5 (permalink) Old 05-11-2012, 04:04 PM
 
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you can not convert a Pontiac 400 into a Pontiac 455 with a bore alone.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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