389 vs 400 - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 05-12-2012, 02:06 PM Thread Starter
 
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389 vs 400

Hi. New here and looking for some advice. Just got a 65 GTO and am starting to restore her from the ground up. Car came with a 400 in it but I have the original 389 block, crank, pistons and heads. There pretty rusty from sitting out on the salt air. Wondering which motor to invest in for rebuild. Want a weekend warrior when done. Not a 1/4 car but a red-light runner. Would like around 400 horses. Any advice would be appreciated.
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post #2 of 9 (permalink) Old 05-12-2012, 05:26 PM
 
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Easy Call for Me

Go with the original. The numbers will be correct and the car more desirable therefore worth more. Harder to find nowadays.

Had a '66 389 3/2 growing up. Blew up the motor and replaced it with a 400 -- always regretted it. Did have enough sense to use the 3/2 setup on the 400. Of course sold the car for peanuts when gas went up.

Took me 30 years to get another one. Wish I still had that '66.
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post #3 of 9 (permalink) Old 05-12-2012, 05:56 PM Thread Starter
 
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Thanks. That's how I felt to but had friends tell me to go bigger. Can I get 400 or so up out of 389 with 3/2?
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post #4 of 9 (permalink) Old 05-12-2012, 07:31 PM
 
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389 tri-power will make 400 HP no problem with the right set-up... welcome

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post #5 of 9 (permalink) Old 05-13-2012, 02:37 AM
 
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not much piston choice if bore is necessary. 400 to me offers more flexibility. Keep 389 intact when going back to original. Run 400 in case it blows or pump fails, which happens.
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post #6 of 9 (permalink) Old 05-13-2012, 09:30 AM
 
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You can bore the 389 out to use 400 pistons. But the valve reliefs are different between the 2 motors. Per many on here, if the cam isn't huge that isn't an issue.

Burning rubber since 1982!!
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post #7 of 9 (permalink) Old 05-13-2012, 09:38 AM
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BTDT, more than once. My take: build the engine that's in the best shape. The 389 sounds like it might not be buildable due to corrosion and rust pitting. Lifter bore sleeving and cylinder sleeving can be done, but are expensive. A 389 and 400 block are about the same. I prefer the 389 in the early cars because it has more "cache" to it than "400" It just sounds better.....like 396 sounds better than 402. Custom pistons are the way to go with either engine, as you will then be able to run the original heads on pump gas, so there will be no difference in build cost. Rods are likewise: forged Eagle rods or comparable are the same part for both engines. If the 389 is rebuildable, you may want to oil it up and mothball it and build a consumable engine for the car....that way, if it does grenade, you still have the #'s matching engine, and the car's value will not degrade. Up to you. Either engine will pull like a frieght train.
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post #8 of 9 (permalink) Old 05-13-2012, 01:10 PM
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...with Geetee

Ask yourself this question: who are you building the car for? Yourself or someone else? If you're building it to please someone else (in other words, trying to maximize resale value) then 100% original is usually the safer bet. However, if you're building it to please yourself, then forget about resale value and build what makes you happy.

If you want a drivable, stoplight-to-stoplight car that will be fun to drive and will be able to embarrass most of what might pull up beside you, then build the 400 and strongly consider going with a stroker kit and building it into a 461. (For reliability you want to replace the stock cast rods with good forged ones anyway, and adding the cost of a good cast 4.25 stroke crank and a good set of forged pistons isn't -that- much more). Plus 389 parts are getting hard to get, even in the aftermarket, so you might wind up boring the 389 to a 400 bore size anyway. Save the 389 block for the day when you might want to maximize resale value and sell the car. Build the 400 (or 461) to maximize the width of the smile on your face.

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post #9 of 9 (permalink) Old 05-13-2012, 10:33 PM
 
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Or you can put in a 326 0r 350, then just lie and say it is a 389, very hard to tell by looking, plus it is good practice for when the wife asks about the car ......
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