400 or 455? - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 01-20-2008, 10:30 PM Thread Starter
 
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400 or 455?

I'm getting ready to build another engine for my 66 gto Cannot decide which would work the best 400 or 455. Any body have any suggestions? I already have a set of 670 heads and a set of 455 4x. Also have a roller cam 236/224 @.50.
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post #2 of 10 (permalink) Old 01-21-2008, 03:31 AM
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Is the 400 a 9786133 casting from 1967? If so what is the letter code?

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post #3 of 10 (permalink) Old 01-21-2008, 07:15 AM
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If the 400 is the correct block for the car I would do that, if not, then the 455 would be getting the treatment.
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post #4 of 10 (permalink) Old 01-21-2008, 08:50 AM
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389 would be correct for 66, the 400 with 670 heads would allow for more HP, the 455 with the heads listed will have a lower CR and they have smaller valves.

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post #5 of 10 (permalink) Old 01-21-2008, 09:03 AM
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How about the 400 heads on the 455 block? Could he do that?
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post #6 of 10 (permalink) Old 01-21-2008, 09:14 PM
 
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Yes. I have a 455 block w/670 heads in my 67.


67 Post Coupe,
69 RA III Judge
06 BOM, M6, 18's
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post #7 of 10 (permalink) Old 01-21-2008, 09:59 PM
 
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I prefer a 428 with some open chamber heads
but using the parts you have I would go with the 400 and the 670 heads
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post #8 of 10 (permalink) Old 01-26-2008, 02:12 PM Thread Starter
 
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What kind of compression do you have with 670 heads on a 455? I would like to use pump gas.
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post #9 of 10 (permalink) Old 01-27-2008, 11:02 PM
 
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I say 455. I am running a 70 455 H.O. 64 head in my 66 hardtop and a 73 455 with 78 6x heads in my 78 Trans Am SE. both 30 over
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post #10 of 10 (permalink) Old 01-28-2008, 04:38 AM
 
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I was running a 1970 455 with 670 heads with a rooler cam for years just switched out the solid roller cam to hyd cam and put eldebrock heads on i like that set up better can actually drive car and not worry about breaking stuff like with that solid cam.

If it isnt a GTO then why are you driving it.[email protected]
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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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