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Discussion Starter #1
What would you do?

looking to build for my 67 gto clone a street car

I have a 400 complete with 6x heads and just picked up a 455 short block

I also have a good set of 64 heads

Thanks
 

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good question you pose that's worth chatting about. i'll say use the 400. more driver friendly and seems like it is ready to go right now. the 455, although has more potential for big power, is heavy and much more costly to build. that's my opinion anyway. thanks for asking.
 

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Discussion Starter #3
Forgot to say that they both need a rebuild
Im just looking for some opinions on what anyone would do
With that its just a street car and it don't need to have a ton of hp but just some to enjoy!
 

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if they both need a re-build i'd say stroke the 400 and get the best of both. These days the aftermarket stroker kit can get you all the cubes you desire with the better (smaller) 400 crank bearings. Forged rods are a must, no need for forged crank and pistons unless you plan to push it over 500HP which by the way is easily done with the right heads and cam. Once you push the cubes up with the bore the 6x heads should be just about right for 9.5:1 compression for pump gas, and even with a mild street cam you'll be in the low to mid 400HP/450TQ range and good up to 5,500 RPM redline.
 

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If it were me, and it's a street car (not a race car) I'd build the 4oo and not stroke it.....I'd go with the 64 heads (the holy grail head for a 400, being big valved, screw in stud, and 87cc chambered). It would be a low cost build, because you would not need a new crank or special pistons. With the right cam, it would be a solid, reliable performer. Depends what you really want, though. I've put over 78,000 miles on a similar rebuild I did on my '67 GTO, and it's been reliable, economical, and fun for the past 25 years as a street cruiser.
 

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Depends on your goals and your budget. For a mild streeter I like Geetee's ideas. For big power I'd also go with the 400 and build a stroker motor. The 400 is inherently stronger than the 455 because of the smaller main bearing journal size and it also doesn't have some of the oiling problems that a 455 can. The 400 and the 455 will weigh the same - so that's not a consideration. With a stroker crank you can easily get to 461 cubic inches using a 400 block and you can make some pretty serious power with it depending on (again) your budget and your planned operating regime. I built a 461 out of my 400 for my 69 GTO. It has run a best of 11.86 @113 mph at 4000 lbs race weight, and we just got back from a 2800 mile road trip in it (the Hot Rod Power Tour).

Bear
 

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I used #15 heads, which are smaller valve heads but the same chamber size as 64's. I couldn't locate any 64's for a reasonable price, or I would have gone with them. Horsepower? I have no idea, but it's less than the stock 335, more than likely. But it'll pass about anything on the road with ease, and it gets over 20mpg at 75-80mph all day long with the Bonneville salt flat gears I'm running. 500 horsepower is nice, but very expensive and not always practical for a street driven car. I drive my cars on the street, and for long distances on vacations.
 

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Discussion Starter #9
why all the preferance for the 400? cost? strength?
It seems the 455 is a more sought after engine.
 

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Before the stroker kits became available/affordable the 455 was the stump puller for torque but it's RPM limited with the bigger main crank journal (more bearing surface, more friction, less oiling, thinner main webbing in the block). The 400 can now be built to 462 by boring and stroking it and with the right parts can rev over 6000 RPM. Really depends on how you plan on driving it. Other considerations are what trans and what rear gear you will use. I have a 12 bolt with a 3:55 gear sitting in the shop for the Tempest and after doing a 2 hr freeway drive this weekend and getting nearly 20 mpg i am liking the stock 2:56 gear in it quite a bit. Chugged along at 70 at 2100 RPM and 70 to 100 was a quick trip and still 1000 RPM under my redline. I had a passenger and it was the first real over the road test since the full retooling of the car, but no doubts it would bounce the speedo off the peg. Horsepower sells engines, torque moves objects.
 

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why all the preferance for the 400? cost? strength?
It seems the 455 is a more sought after engine.
Strength. And like Instg8ter says, 455 used to be the popular engine before the availability of stroker kits. Now the stroker motors give you the same (or more) power without the disadvantages.

BEar
 

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What would you do?

looking to build for my 67 gto clone a street car

I have a 400 complete with 6x heads and just picked up a 455 short block

I also have a good set of 64 heads

Thanks
Since you already have the 455, I'd build it, providing it is a good buildable engine. A 455 is plenty strong for a street car, and it doesn't cost much more than a 400 to build. If the 6X heads you have are 400 heads, they work great on a flattop 455 and already have hardened exhaust seats. The 6X's flow comparably to the #64's. As Bear said, the 455 and 400 weigh about the same, and they are both fairly heavy. If you gotta have the weight, you may as well have the cubes, IMO.
 

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Discussion Starter #13
Thanks for all the info guys, I am really new to all this and I am just trying to get a better idea of what works best and why.I know a lot is personal preference and that's why I found this forum for some answers. Bear gave me some great advice on stroking the 400 in another thread. Theres something about the 455 that intrigues me when someone asks whats it the car? Im 47 and jumping in with both feet on this car because as a teenager it was something I always wanted to do and now I have the chance. Once again thanks and I look forward to everyones opinions.
 
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