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145 Posts
Discussion Starter #1
1965 GTO WT-code 389 long block

I also have this engine listed on Hemmings Motor News. Many of the pictures I wanted to upload are too large. They can be viewed on my ad in the Hemmings Motor News.


Correct standard engine for 1965 GTO with manual transmission. Block part number 9778789. The date code appears to read D75. I believe that would indicate a manufacture date of April 7, 1965.
Approx. 12,000 miles on rebuild. It was in my car for over 13 years. This engine can be re-fitted replacing with what I am keeping off for my numbers-matching engine, installed in another car, and run. The rope-type rear main seal leaks and should be replaced prior to installation. It will also need a dipstick. The one to my numbers-matching engine had the tip broke off, so I am keeping the one off the for-sale engine.
Standard bore
correct 067 cam
correct #77 heads (standard rocker arms with poly locks)
Inside of engine painted with Glyptal

Engine was built by a machinist friend who had a ’65 GTO he bought new. He put a 421 in his car and rebuilt the 389 when it had 40,000 miles for his ’57 Pontiac street rod. He did not bore the block. He honed the cylinders and installed Badger pistons. It has the Arma Steel crank (.010 on the rod and main journals) and likely stock rods. He assembled the engine with wider tolerances to reduce friction. It is noisy during a cold start and quiets down as it reaches operating temperature.
I installed the engine as I acquired it while restoring my ’65 GTO convertible. I never had any trouble with this engine, and it would still be in my car if I didn’t have my numbers-matching engine to put back into my car. It has great low-end torque along with a smooth idle. Perfect for the street.
I have video of the engine running cold and running at operating temperature. I also have a couple of videos of the engine in my car during a drive. The video can be seen on YouTube. Enter my channel Mikeyshouseofbrakes in the search box. One of the videos is a drive in my car. The video is long, and I ramble on with redundant information. You might want to cut through it and watch the snippets you need.

Sold as a long block, but also includes:
timing cover
water pump
oil pan
original chrome rocker arm covers (re-chromed by Industrial Plating Co. in Omaha)
correct intake manifold (port-matched)
pushrod cover
balancer hub and crank pulley
correct cast iron distributor re-curved to full advance at 3,000 rpm.
correct fuel pump (rebuildable core)

Asking price is $3,500. Buyer is responsible for shipping costs. I can deliver within a 100-mile radius of Omaha. This engine is ideal for somebody restoring a ’65 GTO and wants a correct WT-code engine. This is not some 389 two-barrel engine out of a ’65 Catalina with an automatic transmission.
I’ve seen bare WT blocks for sale at Franks’ Pontiac Parts for $1,500. These engines are getting hard to find and this one has never had the cylinders bored and it runs well as is.

Call or text 402-709-6331.


Premium Member
680 Posts
I'm am really tempted, but ideally need a WS motor....

Do you know the compression ratio of the motor?


145 Posts
Discussion Starter #3
The compression ratio is the factory ratio. Advertised it's 10.75:1. Many Pontiac people say the compression ratios were overstated by a half point. So I guess it would make my engine compression ratio 10.25:1.

I did not have detonation issues (pinging). I had the engine timing set to where I didn't have pinging issues. I wasn't racing it, but I drove it the way I wanted.

I use BP Ultimate 91 octane fuel.
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