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post #1 of 5 (permalink) Old 07-10-2009, 05:01 PM Thread Starter
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New Guy with a lot of Questions

OK, my father and I are building a 1966 GTO hardtop, ground up with a multitude of parts put together over the course of several years and through the purchase of two tempest parts cars and the GTO project car. At any rate, this will be the first of what are probably many questions to come. Several years back I bought a 455 and turbo 400 and had them rebuilt. When we got the hardtop car, the man we purchased it from said it had a professionally built 455 in it. It also had a Muncie four speed and tri power setup. We are currently in the process of deciphering all the casting codes but it appears that the 455 was initially a 1966 389 engine. Unfortunately, the heads appear to be off of a 1968 400 engine. It looks like the the original manifold. We haven't checked the carburetors yet, but are suspicious that they are reproductions. We're trying to follow up on the transmission. What I'm thinking, if a lot of this stuff matches up, we might try to keep it and restore it as a set. If it's not close to numbers matching though, what does a good rebuildable (it runs and holds oil pressure) 455 (originally 389), a Muncie four speed, and tri power setup bring in your area? It may not translate to mine, but I don't have another idea of how to value this stuff. Any help would be appreciated.
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post #2 of 5 (permalink) Old 07-10-2009, 08:46 PM
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I don't think you can make a 455 from a 389.

1964 400 4 speed Roller cammed RoadRacer
1969 400 T400 auto 2nd owner
2004 LS1 6 speed modded for roadracing
1966 GTO Altered wheelbase former 1970s show car
1973 Challenger 360/727
1931 Ford Model A
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post #3 of 5 (permalink) Old 07-11-2009, 03:14 AM
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If you want to be certain about what you have for a motor, check your numbers against this reference site, I believe they are about 99.99999% accurate.


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post #4 of 5 (permalink) Old 07-13-2009, 10:44 AM Thread Starter
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No doubt

The engine is definitely a 1966 389. I don't really know how it's been modified. The fellow we bought it from said it was a 455. I think that he knew more about buying and selling stuff than cars though. At any rate, that's not really the information I'm after, although it is helpful. I need to know what this stuff is worth. What would be good asking prices for parts like this.
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post #5 of 5 (permalink) Old 07-13-2009, 03:39 PM
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i can buy the mystery motor in the car running, let me know when and were, post pics. really a 389 into a 455 is just not going to happen. too much custom work. cut crank, open block, custom pistons, rods. your 389 is a 389 or 400. if you have 400 heads on it then you have 400 pistons in it.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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