# trying to identify motor



## Montegto (Nov 24, 2020)

hi i am new to this forum, and hope someone can solve mystery. I just bought a 1966 gto convertible. although it was advertised with 389, i suspected it wasn't. i really liked the car regardless and already have another one with 455 and love it. anyway the casting # in back is 9790071 which corresponds to 68 or 69 400 I believe. it has YS on front. what confuses me is the date code shows B136 which according to my research is feb, 13th 1966. how is this possible.
other numbers i noticed is 522970 above the YS. and CM10 on heads i believe. thank you all for your help


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## PontiacJim (Dec 29, 2012)

Montegto said:


> hi i am new to this forum, and hope someone can solve mystery. I just bought a 1966 gto convertible. although it was advertised with 389, i suspected it wasn't. i really liked the car regardless and already have another one with 455 and love it. anyway the casting # in back is 9790071 which corresponds to 68 or 69 400 I believe. it has YS on front. what confuses me is the date code shows B136 which according to my research is feb, 13th 1966. how is this possible.
> other numbers i noticed is 522970 above the YS. and CM10 on heads i believe. thank you all for your help


You may have a pieced together engine. Looks like 9790071 is 1968/69 block, so maybe B13*8*? YS corresponds to 1968/69.

Not sure what CM10 is coming from. You should see a 2-number casting on the center exhaust outlet on the head which ID's the head. Could be #16? The date casting in just below the valve cover towards the rear if looking at the driver's side, front if looking at pass. side.









How to identify Pontiac engine blocks


Matching those numbers




www.hagerty.com


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## Montegto (Nov 24, 2020)

PontiacJim said:


> You may have a pieced together engine. Looks like 9790071 is 1968/69 block, so maybe B13*8*? YS corresponds to 1968/69.
> 
> Not sure what CM10 is coming from. You should see a 2-number casting on the center exhaust outlet on the head which ID's the head. Could be #16? The date casting in just below the valve cover towards the rear if looking at the driver's side, front if looking at pass. side.
> 
> ...


ok thank you! i will double check


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