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post #1 of 7 (permalink) Old 11-05-2010, 08:02 AM Thread Starter
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400 ho

Always wondered, what makes a 400 HO special from a regular 400?
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post #2 of 7 (permalink) Old 11-05-2010, 09:02 AM
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An 068 cam instead of an 067, and open element air breather, and special high flow exhaust manifolds. Oh yeah, the block code is different, too....WS instead of WT for the stick cars. For automatic cars, YS is the base 400, I forget what the HO auto code is, but it's easily looked up.
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post #3 of 7 (permalink) Old 11-05-2010, 09:20 AM
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I'm not sure if it's applicable to all years, but I believe HO's had large valve heads. My 69 has #48's which I believe they only put on stick shifts and Ram Air 3's. 428 used the same heads as well as the 350 HO that year. Pontiacs used so many different head castings it's almost insane.
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post #4 of 7 (permalink) Old 11-05-2010, 09:27 AM
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Originally Posted by geeteeohguy View Post
an 068 cam instead of an 067, and open element air breather, and special high flow exhaust manifolds. Oh yeah, the block code is different, too....ws instead of wt for the stick cars. for automatic cars, ys is the base 400, i forget what the ho auto code is, but it's easily looked up.
yz ........



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post #5 of 7 (permalink) Old 11-05-2010, 09:50 AM
 
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Valves= 2.11 and 1.77.....as i recall



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post #6 of 7 (permalink) Old 11-05-2010, 11:54 AM
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All standard and HO GTO 400's had the same, big valve heads........#670's. Even some of the early ram air '67's used this head.
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post #7 of 7 (permalink) Old 11-05-2010, 06:26 PM
 
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After 66 all non-2 barrel heads had 2.11/1.77 valves, including the mid 70's 6X heads. I don't know if some of the heads flowed better or what. Round port RAIV heads def flowed better, but that's not the question..

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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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