would a 1969 gto hardtop be able to function with a 454 big block?


Asked by Oct 12, 2007 at 12:24 PM about the 1969 Pontiac GTO

Question type: Car Customization

would a 1969 pontiac gto be able to run with a 454 big block and if so what would the gas milage be?

12 Answers


I wouldnt see why not, you may have to modify the motor mounts and trans to adapt. But is your GTO Judge a stocker? I would keep it that way :)


Agreed, no sense butchering a classic. Get a junker and fix it up if you want to experiment with hotrodding.


I agree with littlehorn and Krez 100 percent. This car has become a valuable collector's item and its collector value would assuredly drop if modified in such a way. As to gas mileage of the 454, that would be impossible to say as there were several different versions and an uncountable amount of modifications possible. But generally speaking if you have to ask about gas mileage, you don't need to consider a 454.



There are plenty of 400 blocks out there that will be a direct bolt-in, and they can be built up and bored out to fit practically any application you have in mind. Take the original motor out and store it, these cars are becoming very valuable! If mileage is your concern, you can get a direct bolt-in 700 or 200r4 overdrive depending on what's in the car now.


If you do happen to do that to a 1969 GTO, then why not put the Pontiac 455 BB in it instead of the 454. It does take motor mounts to be changed. You would also either have to shave the firewall up to two inches or put an electric fan on it. But don't do it, because a 1969 GTO stock is a lot of loot... buy a junker and try it out. And about the gas mileage... who worries about gas when they are putting a BB in a car?

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And a turbo 400 would definitely hold the power of a BB... no 700R4 would. The 700R4 in my S10, lost its forward sprag (underdrive and overdrive didn't function), when I was pushing 350 horses...

454 will fit , change motor mounts on the chasis , the tranny has to be changed & most likely the drive shaft , & a few snip & tuck of a few wires & plugs. if you're going to use headers it might be tight by the steering column . is this a 4 speed or auto? if its a 4 speed just change the bell housing if it's an automatic it has to be changed . or you can just drop a nice 400 or 455 & not change a thing,just sayin.

4 people found this helpful.

Keep it all Pontiac ! The 400 or 455 with Edelbrock aluminum heads, good cam,intake and ignition wiil get you lots of torque and horsepower. And it will bolt right in....


i'm not even gonna answer this !

1 people found this helpful.

454 will fit, need chevy belhlousing or auto transmissision, chevrolet motor mounts and other stuff that is readily available for the GM a body

1 people found this helpful.

It is the same. frame...BodyA

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