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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, 06:59 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.
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, 07:10 PM
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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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Last edited by ZeGermanHam; 05-19-2021 at 07:16 PM.
  #5  
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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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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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 05-20-2021, 11:58 AM
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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?
NOPE. Useable 400 blocks are far more common than 455s these days. ALL stroker cranks will fit in a 400 block with minimal grinding. What you will have is a 3” main 455 with far lower bearing speeds, which is an Achilles’ heel of the 3.25” main Pontiac engines.

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Old 05-23-2021, 05:45 PM
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NOPE. Useable 400 blocks are far more common than 455s these days. ALL stroker cranks will fit in a 400 block with minimal grinding. What you will have is a 3” main 455 with far lower bearing speeds, which is an Achilles’ heel of the 3.25” main Pontiac engines.
The 3.25 mains might be the Achilles heel of the big PMD engines but for 95% of users it does not matter at all.
If you are big time drag strip or roundy round racing sure.
I have a 455 over 500 HP for years and years. One of the reasons it has lasted is I have refused to use any main bearings with only the single round oil hole in the middle.
The shot of oil comes from the tab side of the 3 holes that intersect and if you do not drill a hole in your main bearing that oil has to hit the back of the bearing, mover over and go through the stock hole location.
By that time the crank oil hole has gone by. Fine if a stock grandma,s station wagon but in a performance use you will starve your rod bearings at high RPM.
I even drill our the race bearings with a oil slot vs round hole on 3" main bearings.

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Old 05-20-2021, 11:56 AM
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Store the 389. Build up the 455. Two bolt mains good up to 600HP. Good advise from previous post.

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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 05-23-2021, 07:15 PM
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Quote:
Originally Posted by The Champ View Post
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.
My original 64 389 Tri-Power engine has been on a engine stand for many years and a basically stock 455 engine (Block and crank with good rods and TRW pistons) has been in the engine bay for most of that 20 year period.
The engine now has aluminum heads on it vs the factory heads. I am going away from the solid lifter stuff and will run a flat tappet Hydraulic cam with Rhoads lifters otherwise I would leave it alone. . The engine has HO Try-Y headers.

Remove the early engine and oil it up and store it away and go with the basic 455 engine. The car will be a enjoyment to drive and still perform a lot better vs the 389 engine.

Tom V.

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Old 05-24-2021, 10:32 AM
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Quote:
Originally Posted by Tom Vaught View Post
My original 64 389 Tri-Power engine has been on a engine stand for many years and a basically stock 455 engine (Block and crank with good rods and TRW pistons) has been in the engine bay for most of that 20 year period.
The engine now has aluminum heads on it vs the factory heads. I am going away from the solid lifter stuff and will run a flat tappet Hydraulic cam with Rhoads lifters otherwise I would leave it alone. . The engine has HO Try-Y headers.

Remove the early engine and oil it up and store it away and go with the basic 455 engine. The car will be a enjoyment to drive and still perform a lot better vs the 389 engine.

Tom V.
Tom,
I hope we get to hear about you driving the GTO, here one of these days!!!

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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, 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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