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Discussion Starter #1
Hello everyone!

First, apologies if I describe anything incorrectly or misidentify a part below... Please correct me so I will learn from my mistakes.

So I have a 1965 GTO which I thought had an original engine but after research I am almost positive it's not. I have shown it to multiple people who have all told me various things (You have a 398... You have a 400... etc.)

Recently I noticed that as the car warmed up I would almost stall when giving it gas from a red light or stop and I could smell gas as if it was spilling out, etc.
I decided to bite the bullet and skip rebuilding the carburetor as it's an older Carter 9635SA and am getting a new Edelbrock 625 installed (basically new version of same carb).

Since having the car, there's been oil and grime building around the valley pan gasket so I decided to replace that as well since the carb was coming off and of course since I am pulling the carb off, why not paint and clean the intake manifold and get everything nice and clean before it's put it back together.

So my questions below are based on the pictures that I have included in this link: https://photos.app.goo.gl/WJhxmrTSjarwYWr5A

1. Is there any way to identify this engine as a 389 or 400 from the pictures?
2. Based on the exposed engine, how does everything look to you? I am a novice so everything looks really clean to me. I was told the engine was re-built about 8000 miles back so this possibly makes sense.
3. Does the one rod (Cylinder #1 I believe) that is a different color mean anything and should I do anything about it?
4. Any suggestions of other work I should be doing while the engines apart? I am not looking to spend more $$$ than I already have to but I figure it would be good to make changes if this is a good time to do so.

They are going to re-paint and clean everything as well as re-route and replace most of the old wiring to make things look nicer when done.
Fingers crossed all goes well :)
 

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The engine appears to be a 1965 389, WA block code, from a full size Pontiac. WA code shows as being a 2-barrel, 8.6 compression, 256 horsepower engine having a manual transmission. The heads are cast "75".

389 engine has 2 freeze plugs while the 400 has 3 - so quick check will tell you what you have. The HEI distributor of course is late model, not original.

Best way to find out what the original engine is would be to order the PHS documents for your car and this will also verify that your car is indeed a GTO and not something altered or cobbled together - very easy to fake a 1965 GTO.

From what I read, the carb you have is a Carter AFB, 625CFM, used for a small block Chevrolet and calibrated as such and may not work so well on a Pontiac without some tweaking.
 

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Discussion Starter #3
389 engine has 2 freeze plugs while the 400 has 3 - so quick check will tell you what you have.
Thank You for the quick reply. The engine definitely has three freeze plugs with two on one side of the block and a single on the other side of the block.
I have the PHS documentation (attached) which shows it was originally a 389 GTO with an automatic transmission.

Screenshots of Build Sheets attached.
 

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"...The engine definitely has three freeze plugs with two on one side of the block and a single on the other side of the block..."

He meant either 2 on EACH side, or 3 on EACH side.

You can enter the WA block code & see all the Pontiac engines that used this code. The only WA code 389's were in '65 & '66. Both were 2-barrel engines.

http://www.wallaceracing.com/enginesearch4.htm

Also, most 400 engines had the numbers 0 0 cast into the block on the pad in the center of the lifter valley. Yours has no numbers.

So, if your block does indeed have only 2 freeze plugs on each side, it should be a '65 or '66 389, which originally came with a 2-barrel carb, and was rated @ 256hp.

"...Does the one rod (Cylinder #1 I believe) that is a different color mean anything and should I do anything about it?..."

That's cylinder #2 . Odd numbers are on the drivers side, starting at the front. Even numbers are on the passenger side, starting at the front.

That pushrod was probably swapped in for one that was bent or damaged in some way. Just guessing.
 

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Discussion Starter #5
bigD: Thank you for the correction on the cylinder # and I will have to look again to see how many plugs.
 
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