# '65/'66 flex plate



## 1965 TC4d (9 mo ago)

Hello,

installing a '66 326 in a '65 Tempest.

The flex plate I received with the '66 326 does not fit the engine. May not have come from the '66 326.

The flex plate from the original '65 326 also does not fit the '66 326.

Was there a change in the flex plate between '65 and '66?

Do I need to find a '66 326 flex plate or will others work?

Also I see on ebay there are flex-late shims. Do I need a flex plate 'shim'?

Intend to reinstall the original ST300 auto trans.

Modest auto knowledge and even less when it comes to transmissions.

Thanks


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## LATECH (Jul 18, 2018)

Prolly a chevy flexplate LOL

no kidding , it might be 
63-67 326 has the same size crank hub


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## LATECH (Jul 18, 2018)

Pontiac V-8 Crankshafts


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## 1965 TC4d (9 mo ago)

LATECH said:


> Prolly a chevy flexplate LOL
> 
> no kidding , it might be
> 63-67 326 has the same size crank hub


I completely buy that. All kinds of parts get thrown in with an engine buy many times.

But why wouldn't the flex plate from the original '65 326 work on the '66 326 engine?

Unless of course its not a '66 326. It was sold as a rebuilt 326 but who knows. Will have to confirm when I get back this weekend.

Came with a two bbl intake and un-mounted rochester carb. But even a 455 came with a two barrel so that's no indicator.

And what is a flex plate spacer that I saw on ebay? It that another issue?

Thanks


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## 1965 TC4d (9 mo ago)

LATECH said:


> Pontiac V-8 Crankshafts


This was a very useful link. A 2.6" rear hub was used from '55-'63 and again '76-'81.

Now I wonder if the engine sold to me is perhaps a mid 70s 350 or 350 rotating assembly was used in a 326 block.

Will stop by the shop on Saturday and check some block and head numbers.


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## 1965 TC4d (9 mo ago)

LATECH said:


> Prolly a chevy flexplate LOL
> 
> no kidding , it might be
> 63-67 326 has the same size crank hub


The shop confirmed the engine rear flange will require a 2.6" center hole diameter flex plate. Have seen many 2.5 and or 2.75 but no 2.6" flex plates for sale.

Have seen a flex plate for a '76 350 on ebay. According to the chart '76-'81 engines used a 2.6 center hole flex plate.

Also I don't know if this engine came with and or requires a flex plate 'spacer'. How would I determine if it needs a spacer? Would running without a space cause any problems?


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## LATECH (Jul 18, 2018)

I dont run the spacers. Not sure what they are for.
Never had a problem


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## 1965 TC4d (9 mo ago)

LATECH said:


> I dont run the spacers. Not sure what they are for.
> Never had a problem


Thought they might be associated with the flex location in relation to the starter.

Good to hear they can be run without the shim. I'll go that way too.

Thanks


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## PontiacJim (Dec 29, 2012)

1965 TC4d said:


> Thought they might be associated with the flex location in relation to the starter.
> 
> Good to hear they can be run without the shim. I'll go that way too.
> 
> Thanks


Should be easy enough to ID using the date casting numbers next to the distributor. 2-freeze plugs or 3 will also tell you if it is an early block, 1966 and under, or 3 freeze plugs 1967 and later.

Early Pontiac - 1955-'63 2.6" crank register

Mid Pontiac - late 1963- early 1976 2.75" crank register (listed as 2.76") - 326CI falls into this category as well as a 350CI.

Late Pontiac - late 1976 - 1979 2.5" crank register (listed as 2.6") 350CI falls into this category, no 326's.


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## 1965 TC4d (9 mo ago)

Well taken. And agreed.

Clearly should have done so before I bought the engine. 

Coming back from the store this morning I stopped by the shop and it was closed. Will get over there early next week.

The shop indicates that the rear flange is about 2.6". 2 9/16?

Will also try and see what kind of balancer and or damper the engine has up front. Seems there are balanced and unbalanced plates.

Still hard to figure how this engine would have a 2.6 rear flange. Was advertised as a rebuilt 1966 326. Shop that removed it from a car that was in a crash indicated that the NAPA next door rebuilt the engine.
Bolts are not painted like the rest of the engine and can see new gasket ends.

None of this is determinative I know. But still odd if it in fact does have a pre-64 crank with the 2.6" flange.


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## 1965 TC4d (9 mo ago)

PontiacJim said:


> Should be easy enough to ID using the date casting numbers next to the distributor. 2-freeze plugs or 3 will also tell you if it is an early block, 1966 and under, or 3 freeze plugs 1967 and later.
> 
> Early Pontiac - 1955-'63 2.6" crank register
> 
> ...


Turns out there was a 326 in '63 and it was in the Tempest. Engine was from a second hand seller and could have simply gotten the year wrong.

Would explain a lot.


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## 1965 TC4d (9 mo ago)

PontiacJim said:


> Should be easy enough to ID using the date casting numbers next to the distributor. 2-freeze plugs or 3 will also tell you if it is an early block, 1966 and under, or 3 freeze plugs 1967 and later.
> 
> Early Pontiac - 1955-'63 2.6" crank register
> 
> ...


Bad news. If it does turn out to be a '63 326 it appears the flex plate is a one year only thing.

Post from forum:

My parts manual shows a part number for a 63 T8 auto flywheel--9772669 and a number for a flywheel reinforcement plate--9772675. They are one year only numbers and don't show up on any other models or years. It does say the flywheel has 155 teeth on the T8 and 166 on the P8 model.
You may have to straighten the one you have or be ready for an extensive search!

This part is probably so rare that it may explain the sale of the rebuilt 326 and labeling it as a 1966.

May I ask if there is a spacer or other part that would allow the use of the original '65 326 flex plate, or another Pontiac plate, on the '63 2.6" flange.


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## PontiacJim (Dec 29, 2012)

1965 TC4d said:


> Bad news. If it does turn out to be a '63 326 it appears the flex plate is a one year only thing.
> 
> Post from forum:
> 
> ...



Re-read Post #9. What year is the engine block?


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## 1965 TC4d (9 mo ago)

Head code 140 -'67 326

Block code 9778840 - '65 326

Appears the snout is the longer, 3.00" which would make it a '76-'81. The only other series of cranks with the 2.6" rear flange hub were the '55-'63 and they had a 2.5" snout. (pretty unlikely its a '59-'63 389 crank from a rebuilder)

Going to source a '76-'79 350/400 flex plate and see if it bolts up the the small 2.6" rear flange/hub. (hoping that drives the ST300 torque converter)

If it fits, the engine, which is already in the car, and trans should connected and in the Tempest soon.

Will report back if the '76-'79 flex plate bolts up to the small 2.6" hub.


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## PontiacJim (Dec 29, 2012)

1965 TC4d said:


> Head code 140 -'67 326
> 
> Block code 9778840 - '65 326
> 
> ...



OK. That block casting number was used for 1965-66. 

The 350CI crank would also tell you the engine was rebuilt. Why not take the 2.5 flywheel to a local machine shop and have then open the hub hole to 2.6? Probably be cheaper than purchasing the correct one plus the shipping charges.


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## 1965 TC4d (9 mo ago)

PontiacJim said:


> OK. That block casting number was used for 1965-66.
> 
> The 350CI crank would also tell you the engine was rebuilt. Why not take the 2.5 flywheel to a local machine shop and have then open the hub hole to 2.6? Probably be cheaper than purchasing the correct one plus the shipping charges.


Good thought. And would do exactly that now that I know what rotating assembly is in there.

The original flex plate that came with the car is a 2.75. The flex plate that came with the '66 engine does not appear to be a Pontiac plate at all and does not work.

If the 350/400 plate comes in the 2.5" hole size will do as suggested and open the hole to work.

Would you know if there is some reason the 350/400 flex plate would not work with the ST300 TC?


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## PontiacJim (Dec 29, 2012)

1965 TC4d said:


> Good thought. And would do exactly that now that I know what rotating assembly is in there.
> 
> The original flex plate that came with the car is a 2.75. The flex plate that came with the '66 engine does not appear to be a Pontiac plate at all and does not work.
> 
> ...


Not aware of any issues as many will opt to swap in a TH-350 for the ST-300 and have not had anyone say they ever had an issue in that the flywheel did not work, so gotta believe you are good to go. Your local craigslist or facebook marketplace should be an easy source for a good flexplate. Personally, would not pay $50-$75 and that may be high.


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## 1965 TC4d (9 mo ago)

PontiacJim said:


> Not aware of any issues as many will opt to swap in a TH-350 for the ST-300 and have not had anyone say they ever had an issue in that the flywheel did not work, so gotta believe you are good to go. Your local craigslist or facebook marketplace should be an easy source for a good flexplate. Personally, would not pay $50-$75 and that may be high.


Appreciate the comments on the ST-300 TC working with a later flex plate.

Are the original used plates preferable to new ones? Better quality? New standard replacement plates, probably east asian, are pretty inexpensive. Of course a stock used plate is probably over 35 years old with unknown miles.

Lower rpm, stock 2bbl engine so not excessive stress.


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## 1965 TC4d (9 mo ago)

1965 TC4d said:


> Appreciate the comments on the ST-300 TC working with a later flex plate.
> 
> Are the original used plates preferable to new ones? Better quality? New standard replacement plates, probably east asian, are pretty inexpensive. Of course a stock used plate is probably over 35 years old with unknown miles.
> 
> Lower rpm, stock 2bbl engine so not excessive stress.


Probably should have started there but I looked up flex plates on the Butler site to see what they offered.

Turns out this issue with matching different flex plates with other crank flange/hub ends is not necessarily an uncommon thing.

Butler sells an adapter ring that would allow the use of the original '65 326 Flex plate, 2.75" mounting hole, with the 2.6" crank flange.

Original flex plate from the Tempest had about 112K miles and appears to me in good condition.

Rather than try and source a flex plate and hope it works I can use the original plate with the rebuilt replacement 326.

Will report back on effectiveness.


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## PontiacJim (Dec 29, 2012)

1965 TC4d said:


> Probably should have started there but I looked up flex plates on the Butler site to see what they offered.
> 
> Turns out this issue with matching different flex plates with other crank flange/hub ends is not necessarily an uncommon thing.
> 
> ...


Perfect, an adapter ring is the way to go then. As long as the teeth on the ring gear look good and not chewed up/missing, then I see no reason not to use it.


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