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1966 GTO w/421 v-8 ?

Posted by Eric F 
1966 GTO w/421 v-8 ?
February 06, 2004 04:12PM
I'm looking at buying a 66 GTO w/ a 421 v-8.

The car looks very nice, but can you give me some opinions on the motor?

In general, is this a good motor, year for the GTO's?

I love the design, I was looking for a good 67', but this 66 really caught my eye.

TIA - The Bigest E from Chicago.
Re: 1966 GTO w/421 v-8 ?
February 06, 2004 08:09PM
I know the 421 v-8 is not original to the car, I would like opinions on the motor in general. I'm not a gear head, and have never really heard of the 421 motor before reading about it on this site today.

The car has bucket seats, power steering and brakes, an AM radio, and It has a 400 B & M automatic trans. The car looks to be in great shape, and is in my price range. The car will be for driving on the weekends with the familly.

Any Opinions???

Thanks !
Re: 1966 GTO w/421 v-8 ?
February 06, 2004 08:25PM
I think the 421s were mostly used in the bigger Pontiacs up till 1966.
Probably the biggest drawback to a 66 GTO with an auto trans is the 2 speed powerglide. Since the one your looking at has a TH400 it wont be a problem.

A 421 was not put in a GTO from the factory. I believe from the outside a 421 and a 389 (which would be original to a 66) look the same. Its possible that the car actually has a 389 but the current owner thinks its a 421 (for whatever reason) You should check the codes on the engine to determine what it really is.
Re: 1966 GTO w/421 v-8 ?
February 06, 2004 08:39PM
How do I go about checking the codes ??

The car is being sold through a used car dealer. I'm sure there not to up on the details on this car.

I had the exact same thought that it's most likely a 389, but most proberly with a 421 air intake. Does that make sense?
Re: 1966 GTO w/421 v-8 ?
February 09, 2004 11:04PM
Try this link
Once you enter the site look down on the right side of the page.
There is a link named "Engine ID"
Once you click it you can choose Pontiac.
This is a great parts suplier and the info on how to ID a Pontiac engine is great!

Hope this helps!
P.S. The site also has some VIN and Body Tag decoding.
Re: 1966 GTO w/421 v-8 ?
February 13, 2004 04:20PM
The 421 engine was created for the 1965 2+2. This was a Pontiac Catalina, gold with white interior, 421 tri-power and a hurst 4 speed tranny. This car was only marketed 1 year. The 421 was experimented with in the 1966 GTO but was turned down. Some of the 421 GTO's were claimed by GM exec's and kind of faded away. There are still some in the basement of Pontiac Motor Division plant along wit tons of other experimental cars.
Re: 1966 GTO w/421 v-8 ?
February 14, 2004 02:45AM
the 421 was made from 1961 thru 1966, also called a 421 sd, short for super duty , the 389 was made from1959 thru 1966 , 389 high performance motors made from 1964 thru 1966 , the 421 was only .030 bored over from the 389 , and has 4 bolt main caps , so in short , it is some what of a collecters item and hard to find , but a very good motor , I wish I had one.

Re: 1966 GTO w/421 v-8 ?
February 14, 2004 08:37PM
There is a difference between the 1959-1964 389 and the 1965-1966 389. The heads and intakes are not interchangable between those two groupings. The Early 421's were alot more power ful than the later some of them being estimated at over 400HP. In 1963 GM did away with these engines and they were detuned. Just a bit of info I obtained through a GTO book. Good luck on the goat. Lance
Re: 1966 GTO w/421 v-8 ?
April 21, 2010 03:00AM
Read your question on the difference between a 389 and a 421 the difference is the bore and stroke, a 389 has 3.75" stroke while the 421 has a 4.00" stroke, the mains are also different the 389 has 3.00" mains while the 421, 428 and the 455 has 3.25" mains, hope this info helps.
Re: 1966 GTO w/421 v-8 ?
March 23, 2011 08:53AM
buying a 66 GTO w/ a 421 v-8 is not a big deal and frankly speaking wonderful cars to have but you have to keep spending lot of money on its maintenance and the biggest issue is parts are also not available so you have get it made for your self so extra charges again you have to pay .

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Re: 1966 GTO w/421 v-8 ?
April 15, 2011 08:32AM
The 1996 Pontiac is a king of muscle car & its have outstanding features. I like its excellent contours and distinctive headlight features. Cars for sale

Edited 1 time(s). Last edit at 04/15/2011 08:36AM by Micheal73.
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