# 400 or 455?



## rod collins (Jan 12, 2008)

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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## 05GTO (Oct 6, 2004)

Is the 400 a 9786133 casting from 1967? If so what is the letter code?


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## Rukee (Feb 8, 2007)

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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## 05GTO (Oct 6, 2004)

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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## Rukee (Feb 8, 2007)

How about the 400 heads on the 455 block? Could he do that?


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## SANDU002 (Oct 13, 2004)

Yes. I have a 455 block w/670 heads in my 67.


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## Jeffs386 (Nov 1, 2005)

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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## rod collins (Jan 12, 2008)

What kind of compression do you have with 670 heads on a 455? I would like to use pump gas.


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## likethat (Oct 5, 2007)

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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## Showgoat67 (Feb 16, 2005)

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.


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