# 65 GTO engine code



## adamrysz87 (Nov 14, 2021)

I was looking for the engine code and only found something like this ...
076497 S1









On web Wallace Racing I found this code: '61 year..... weird









other numbers are just rear of the engine (K10 and 3)









and right side (C048)
*







*


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## O52 (Jan 27, 2019)

Looks to be a 389 from 1961. 
Date code K 1 0 indicates block was cast on November 1, 1960 for the 1961 model year or 1970 for the 71 model year.
Cylinder head date C 04 8 appears to be March 4, 1968

Look on the side of the block. A 455 will have the displacement cast on the side of the block. 

Please show the casting number of the blocks and heads as shown in these diagrams.


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## PontiacJim (Dec 29, 2012)

1961-1964 uses the starter that bolts to the bellhousing. 1964 is the change over year where some blocks will have the starter bolted to the block, not the transmission.

If you have the earlier block with later bell, then you should see this adapter:



https://butlerperformance.com/i-24452959-pontiac-starter-adapter-mount-starter-on-1964-and-earlier-blocks-bpi-p010004.html



Is this your starter?



https://butlerperformance.com/i-24453305-imi-pontiac-389-421-61-64-bell-housing-mount-mini-starter-imi-123.html


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## adamrysz87 (Nov 14, 2021)

Yes, this is my starter.
Everything indicates, this is the '61 block engine.

I have "61 engine block and Muncie M20 '68, 

What kind of clutch and flywheel I need?


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## PontiacJim (Dec 29, 2012)

adamrysz87 said:


> Yes, this is my starter.
> Everything indicates, this is the '61 block engine.
> 
> I have "61 engine block and Muncie M20 '68,
> ...


You have 2 different posts. You said you have a 455? Now you say a 1961 389?

Which engine do you have?

Look at the lower block. How many freeze plugs do you see? 455 will have 3 freeze plugs. 1961 389 will have 2 freeze plugs.

455 will have 11-bolt water pump. 1961 will have 4-bolts.


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## adamrysz87 (Nov 14, 2021)

Sorry, I believed what someone wrote....Now I verify it...

Jim, thank you for your help and knowledge, everything you say is right.

I found 2 freeze plugs on the left side and 2 on the right side.
















I counted 7-bolts around the water pump (maybe not all of them are for the pump).

Jim, what do you think, what parts to look for this engine block and transmission ? (new flywheel and clutch kit)


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## PontiacJim (Dec 29, 2012)

adamrysz87 said:


> Sorry, I believed what someone wrote....Now I verify it...
> 
> Jim, thank you for your help and knowledge, everything you say is right.
> 
> ...



OK, your photo helps to identify the engine. The 2-freeze plugs means pre-1967. I see a casting number on the block that fits 1961 ad 1962.

1961 389 538181
1961 421 538181
1962 389 538181
1962 421 538181 (early built) 

Looking at my list of engine codes, S1 is 1961, 389 CI, 267 HP/10.25 compression, 538177 casting number of the heads, 2 Bbl carburetor, Automatic transmission. The engine code is not found in 1960 or 1962, so it is definitely a 1961 engine block.

Look at the picture of the 4-bolt water pump. The original 1961 water pump will look like it. You can see it uses 4 bolts to attach to the timing chain cover.

If your timing cover/pump does not look like this, then it has been changed to a later timing cover/water pump.










So the block is 1961, and a 389CI. What you do not know is what is inside of the block. It could be a 3.75" stroke crank which is stock, or a custom stroker crank which can be commonly used. It could be a 4.25" stroke making the engine between 447 CI to 454 CI depending on how much the cylinders were bored over. So if you were told it was a "455", it could be the 454" stroker kit. BUT, you will not know unless you disassembled the engine. Take a look at these kits from Butler.



https://butlerperformance.com/i-24591340-butler-performance447-454ci-balanced-rotating-assembly-stroker-kit-for-389-block-4-250str.html?ref=category:1234862



But, that should not make any difference with the flywheel and your starter problems, just only means your engine is a 1961 389CI block and could be anywhere from the stock 389 cubic inches to 454 cubic inches with a stroker kit.

Here is what I think is the problem. With the 1961 block, you have to use the bell housing adapter for the starter. The flywheel may be OK. The problem is that the adapter is 1/4" or 3/8" thick (?) and that extra thickness is moving the starter nose/gear back away from the flywheel ring gear - too much and the starter is not meshing with the flywheel gear.

The starter may be wrong. Wilcap is well known for engine/transmission adapters for all engines and can even make an adapter if you need it. Take a look at the adapter, part #389-350, for the early Pontiac 389-421 and how it is bolted together. This diagram is for a Chevrolet bolt pattern automatic transmission. You can click on the PDF which explains more on adapting a Pontiac transmission. They list the parts used with the kit, and note that they use a Mopar starter.






Wilcap Pontiac Engine Adapter Page


Wilcap engine to transmission adapters for Pontiac and GMC V8 287 316 347 370 389 1955-60 adaptors



www.wilcap.com





Now take a look at what Butler sells as an adapter for the earlier blocks and later 1965 and bell housings. Theirs is 1/4" thick and in my opinion, looks like an adapter I have used for *automatic transmissions* when I installed a 1968 Pontiac TH-400 on to my 1965 Chevy engine - the only difference is that they added the small "leg" for the starter and the 2 bolt holes. My opinion is that it is cheaply made. I* assume *that the starter shown below the adapter and the crank adapter ring are supposed to work with the adapter. But if you have this set-up, it does not work.



https://butlerperformance.com/i-24452959-pontiac-starter-adapter-mount-starter-on-1964-and-earlier-blocks-bpi-p010004.html?ref=search:https%3A%2F%2Fbutlerperformance.com%2Fsearch.html%3Fq%3Dtransmission%2Badapter



So you need to find out more about the adapter you have. It may be as simple as finding another starter with a longer nose so the gear will extend out further. Verify that your flywheel is 166 teeth, otherwise, you have the wrong flywheel - and that could be your problem too.


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## adamrysz87 (Nov 14, 2021)

I took a photo of my adapter. It is very thin and flat. Look at the color of the adapter (a little dirty) and the oil pan, it's the same fresh. The engine was recently rebuilt, the odometer shows 1,645 miles.

























I checked the starters from Hi Torque, they produce two models for the Pontiac IMI-123 and IMI-108. The IMI-123 is 100% the same as mine and is made for early engines (61-64). Looks like new.








I checked again the flywheel has 166 teeth...Maybe the flywheel is wrong?

The second problem is the distance between the clutch and the release bearing.
Definitely the clutch fork is wrong. I checked the numbers 5014090 = Chevelle '64 - '72.

Maximum difference between the engine block and the bearing is 11 cm (4.3 in)









The minimum difference between the engine block and the bearing is 9 cm (3.5 in)









However, from the block to the clutch with the flywheel is 9 cm (3.5 in). This means the bearing can only touch the clutch at maximum deflection.









Jim, are there different pressure plate heights? Someone put on the LUK clutch .. (previously it was Centerforce II) to be sure I would replace the clutch kit and other parts.


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## PontiacJim (Dec 29, 2012)

adamrysz87 said:


> I took a photo of my adapter. It is very thin and flat. Look at the color of the adapter (a little dirty) and the oil pan, it's the same fresh. The engine was recently rebuilt, the odometer shows 1,645 miles.
> View attachment 147516
> View attachment 147518
> 
> ...


That plate does not look like an adapter at all - too thin. It looks like a bellhousing separator plate modified. Take a look at the assorted plates Summit has to offer and you will see what I am talking about. That may be a factory 1961 separator plate that used the bellhousing to bolt up the starter.

It is still a bit thin to handle the torque of a starter, but I wonder if you could buy a *1961-64 starter *and add some plating to the back side of the separator and run bolts and nuts through the starter and plate. I would then secure the starter side by using a flat steel bar or angle iron to hold the starter steady - again, using one of the bolts/nuts you would use to hold it to the separator. The later Pontiac 400 starters used a bracket that went from the motor mount bolt to one of the starter bolts on the back of the starter to give it more support and hold it rigid. Might be something to consider and/or look into fabricating.









Engine To Bellhousing Separator Plates - Free Shipping on Orders Over $99 at Summit Racing


Find Engine To Bellhousing Separator Plates and get Free Shipping on Orders Over $99 at Summit Racing!




www.summitracing.com





Yes on the different pressure plate heights. Some will have flat diaphragm fingers, some will be raised up, there is the 3-finger Borg & Beck which is another design.

Each type of pressure plate will generally require a matching throw out bearing, both length and the correct style of face that sits on the fingers. For example, a flat finger might use a taller throw out bearing while a raised finger might use the shorter throw out bearing.

The correct clutch fork should help. The correct throw out bearing will have the clutch fork arm pushed forward (towards the fan) and almost up against the cut-out that it passes through in the bell housing. If not, then you have the wrong throw out bearing - too short.

They make 3 different common heights in throw out bearings. I have used all 3 in my experiences. Just depends on the pressure plate fingers and how the angle is on that clutch fork coming out of the bellhousing. Kits don't always supply the correct bearing as many kits are for Chevrolet - which may not work for Pontiac.


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## adamrysz87 (Nov 14, 2021)

You have right, the starter is bolted to the bellhousing and this palet it's only a cover. So that's not a problem anymore. Look at the picture below.
























Starter I think is OK (IMI-123 for early engines) and I think I have a problem with the flywheel.

On the Summit website, I found a clutch that looks like mine.









1968 PONTIAC GTO Luk Clutch 04-002 LuK Clutch Kits | Summit Racing


Free Shipping - LuK Clutch Kits with qualifying orders of $99. Shop Clutch Kits at Summit Racing.




www.summitracing.com













Jim, I want to order new parts, what model and year to look for?
I want to buy new flywheel, new clutch fork, new throw out bearing (what height of the bearing?), new stud ball and maybe a new clutch?
Can you help me find, I will be forever grateful.


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## PontiacJim (Dec 29, 2012)

OK, doing more research. Your post is very misleading. You have a 1961 engine and the 1961 bellhousing, not a later 1965 GTO engine or bellhousing that would require an adapter plate.

The clutch fork you have may be correct for your bellhousing? - most of us were saying to get the correct Pontiac clutch fork based on a 1965 and up bellhousing. You also have the earlier flywheel.

I found a photo of a 1964 flywheel that looks like yours. The ring gear is located differently than on the later flywheels, so the starter may not work as you found out.

Here is what I found on another Pontiac site:

"The ring gear is facing toward the rear of the car. It's not close to the crankshaft. There is champher on the side that slides onto the crankshaft register.

1963 flywheels/ring gears are unique to 1963 and earlier full-size cars with BELLHOUSING mounted starters.

The flywheels are unique for the full size 1961-1962 which are the same,1963 full size only fits 1963, and 1964 full size also is by itself. They also had super duty flywheels for 1961-1962, then 1963.

Will a 1964 full size flywheel fit a 1963 engine/car? Yes. Is it right? no. Will it work? Yes, but *you may experience a short starter drive gear or flywheel ring gear life.* Also, *you may find you are at the outer perimeters of your clutch adjustments* (which sounds like what you are expereincing?)*.*

Engines beginning in 1964 used a new designed block which incorporated a block mounted starter used by the 1964 GTO’s. They also used a different flywheel and bell housing than the full sized Pontiacs. The full size Pontiacs used the same new designed engine block just like the GTO, but they used the old-style cast iron bell housing and bellhousing mounted starter and a different matching flywheel.

1964 was an anomaly. In 1964 Pontiac made a small change to the size of the new designed block. To make everything work the bellhousing is different in a full size 1964 Pontiac 4 speed car. The drive gear is far shorter in the 4 speed starter, and the nose of the starter for an automatic will not fit the 4 speed bellhousing."

I think you want to contact Brad at Fabcraft Metalworks out of Southlake, Texas.

This is the phone number provided to make contact 1-800-208-8242.

Here is the website. You could email them for more information and they can tell you what parts you will need for your 1961 engine to make all your parts work, and not guess. They specialize in the older Pontiacs.









Home - Fabcraft Metalworks


1957-1964 PONTIAC AND OLDSMOBILE 9.3" REAR END COMPONENTS - GEAR SETS AND NEW POSI UNITS -ALSO SPOOLS -AND AXLES - BRAKES -- EVERYTHING FOR THE 9.3" AND MUCH MORE - WE SELL NEW 4 AND 5 SPEED TRANSMISSIONS AS WELL



fabcraftmetalworks.com





 Hope that helps.


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## adamrysz87 (Nov 14, 2021)

Thanks Jim, I will be looking for the parts I hope to make it. I'll let you know.


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## PontiacJim (Dec 29, 2012)

adamrysz87 said:


> Thanks Jim, I will be looking for the parts I hope to make it. I'll let you know.



OK. I am sure there is a way to do this, you just have to find someone who works with the older engines and knows the right parts needed to make everything match. The "old" guys who used to know how to do these things just are no longer around.


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## adamrysz87 (Nov 14, 2021)

I solved the first puzzle. Now the flywheel fits. It was enough to remove the spacer behind the mounting plate in the starter.









Now I will order a deep throw out bearing. 
When everything is OK in the transmission, I will be able to start the engine ...

Another question, is it a crankcase ventilation ?


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## PontiacJim (Dec 29, 2012)

adamrysz87 said:


> I solved the first puzzle. Now the flywheel fits. It was enough to remove the spacer behind the mounting plate in the starter.
> View attachment 147664
> 
> 
> ...



OK, simple fix removing the starter spacer- moves the starter deeper so it matches the ring gear.

The PCV valve is what you have circled. On the earlier engines, it is located in the back of the intake. On the later engines, it is in the front. It connects to a port on the carb. You do want to have it connected. You also want to have a breather on one of the valve covers.


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