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Old 05-19-2021, 12:57 PM
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Default Go Big 455 or not?

I have the original 389 out of my 65 GTO, It is a it has never been taken apart or bored over. I also have a 1971,455 complete engine that has never been bored over or any type of machine work done to it.
I want to build a strong street motor. Aluminum E heads, roller cam and rockers and so on.... The question is, do i buy a stroker kit for the 389 to make a 455? Or do i use the 455 to build the strong high horse power that i want? Is the 71 , 455 block a better / stronger casting than the 65 , 389 block?

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Old 05-19-2021, 01:19 PM
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If it were my car, I'd remove the original 389ci and tuck it away. Then I'd sell the 455ci block and use the proceeds to buy a 400ci block and stroker kit to build a 461.

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Old 05-19-2021, 01:49 PM
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Personally I’d build the 71 455. You have it and it is plenty strong. Way cheaper to use the factory 455 crank and just buy rods and pistons. The end result in power and reliability will be the same only a lot cheaper than buying a 400 block and a “stroker” crank. The factory crank is probably stronger than the new cast cranks anyway despite its age. And there are all the parts that readily bolt right on the 455.

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Old 05-19-2021, 02:46 PM
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Stash that original block - there is no since it risking it on a modified build.

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Old 05-19-2021, 03:26 PM
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Let the 389 slumber under the garage work bench
and build the 455.

500 hp and 550 ft lbs should be cake even with Aluminum D port heads!

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Old 05-19-2021, 06:02 PM
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My correctly date coded, '64 GTO 78XW coded, 389 is on an engine stand, complete carb to pan.

I found a standard bore 455 complete carb to pan for $500.00 and went that route for a 462.

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Old 05-19-2021, 06:59 PM
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Quote:
Originally Posted by ZeGermanHam View Post
If it were my car, I'd remove the original 389ci and tuck it away. Then I'd sell the 455ci block and use the proceeds to buy a 400ci block and stroker kit to build a 461.
that’s a lot of effort for a street engine just to go to a 3” main block, no? is the juice worth the squeeze?

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Old 05-19-2021, 07:01 PM
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I vote with the crowd telling you to store the original engine and build the 455 with the factory crank.

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Old 05-19-2021, 07:10 PM
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Quote:
Originally Posted by i82much View Post
that’s a lot of effort for a street engine just to go to a 3” main block, no? is the juice worth the squeeze?
Maybe, but it depends. You can usually find good standard bore 400ci blocks for around $500, and Butler rotating assemblies start at $1800. OP says he wants to build a "high horsepower" motor (a subjective term). By the time you sell the 455ci block, it's within a thousand dollars difference (give or take). And with that in mind, I'd rather have the the 400ci block with the smaller/stronger mains and future-proof it to handle whatever power gets thrown at it down the road. And I assume he'd have to bore the 455ci block anyway, and then new pistons would need to be purchased, further narrowing the price gap.

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Old 05-19-2021, 07:22 PM
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Yep 389 put to bed
Build that bodacious 455

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Old 05-19-2021, 07:25 PM
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Quote:
Originally Posted by ZeGermanHam View Post
Maybe, but it depends. You can usually find good standard bore 400ci blocks for around $500, and Butler rotating assemblies start at $1800. OP says he wants to build a "high horsepower" motor (a subjective term). By the time you sell the 455ci block, it's within a thousand dollars difference (give or take). And with that in mind, I'd rather have the the 400ci block with the smaller/stronger mains and future-proof it to handle whatever power gets thrown at it down the road. And I assume he'd have to bore the 455ci block anyway, and then new pistons would need to be purchased, further narrowing the price gap.
makes sense to me! i guess maybe it depends on his timeline and local availability of a good 400 block.

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Old 05-19-2021, 07:32 PM
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Quote:
Originally Posted by i82much View Post
makes sense to me! i guess maybe it depends on his timeline and local availability of a good 400 block.
Yeah, I'm obviously in the minority here, and I certainly don't fault anyone for suggesting the 455 as a good option. I just think that at the end of the day, there wouldn't be a big cost difference between building the existing 455 vs. building a 461. And because 455s are becoming harder to find, it might also be nice to see it end up in a car that left the factory with a 455.

But I don't feel very strongly about it either way. I think everyone is in agreement to put the original 389 on ice and build the "fun" motor using something else, whatever it may be.

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Old 05-19-2021, 08:21 PM
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Another vote for store the original 389 and build the 455

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Old 05-19-2021, 08:34 PM
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Save the 389, build the 455.
For what you and the vast majority of us do its a waste of time, effort and money to build a "stroker" when a basic 455 is more than good enough.
Once these stroker cranks showed up a lot of people thought there would be a major difference in power and reliability. There is not unless you are pushing the power level to beyond what a PMD block, any of them are safe too. And even then its not much.
A 455 with iron heads are the best street engines around considering you do not have to do much to them to get it done right.

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Old 05-19-2021, 08:42 PM
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A factory 455 block and crank with studded 2‐bolt mains is easily good up to 600Hp. Are you really going to build an engine that makes that much?

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Old 05-20-2021, 09:06 AM
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Ok, the winner is the 455! Thanks guys for your input.
i'll bet this next question might be all over the board. Heads, any and all opinions welcome. I am partial to aluminum heads. Your thoughts?

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Old 05-20-2021, 09:24 AM
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Good decision. The stroker builds are only necessary when you don't have a 455 available to you. You solved that problem.

On heads, you'll have to weigh the cost factor for yourself. I've found redoing 50 year old cast iron heads is a very expensive venture. I generally don't get a pair out of a machine shop for less than $1000 and that's without port work. By the time you buy seats, guides, springs, retainers, valves, and then pay for all the machine work, new guide work, seats and valve job, cutting for positive seals, etc...to have an iron head that flows maybe ~220 cfm, unless you want to spend more for porting, The aluminum heads start to look like a pretty good bargain

I usually do the iron heads for numbers matching type of stuff.

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Old 05-20-2021, 09:58 AM
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Given your trans and gearing, destroking a 455 might be an option.

Pontiac was working on a production 366 roundport motor that "hit the sweet spot" according to engineers but could not get it past marketing. IIRC it had the bore of a 455 but a much shorter stroke. If you are running a 4 speed and 3.55's it may be a much better match.

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Old 05-20-2021, 10:35 AM
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Can’t go wrong with Kauffman, Edelvrock or the Speedmasters. The E heads are tried and true. The Speedmasters are a little less money but flow a little more than the E heads out of the box I think. But horsepower is airflow and the Kauffman high ports flow 330 out of the box. That would be my choice. They can be Cnc ported relatively cheaply by Kauffman. The E heads can too. I had a set of cnc ported by Butler that flowed 340. Very nice too but still I would go highports.

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Old 05-20-2021, 10:42 AM
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Default Been there done that!

I chose to do the 389 in storage and build a iron head 455 - 30 over. 4 speed and 3:55s. Been a really fun car to drive. Did similar in another car and over cammed it for street use. Live and learn. Good luck

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