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in the upper right corner of your picture of the head, there is another casting. clean it off and try to read it...
 

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The 1 looks pretty clear. Other # looks like a 2 to me. What does the passenger side head say? If its the original motor and like you say its a 70 GTO 400 4 speed, then it should be #12 heads. According to the chart in the link #12 were on stick cars, 13 automatics. #11 heads were small valve heads on 350 2 bbl engines.
Pontiac Heads
 

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Discussion Starter #6
The pass side is near impossible to read. The exhaust port to the right of the head bolt in the picture has two "2"s stamped (not cast) into it.
 

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That would be January 16th 1970. Head casting numbers that started with a
"1" were 11, 12(manual and depending on the engine code, RAIII), 13(auto), 15(455) and 16. None started with a 7.
 

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Discussion Starter #10
awesome. thank you. that means its an all numbers matching engine. so how do i go about finding out if its a 11, 12 or so on?
 

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Maybe. What's the 2 character engine code located below the head on the passenger side front of the block? Do both heads say A160? Did you verify the block is a '70? My concern is why the 2 is stamped and not cast. I have some possible theory's depending on what block it is.....

 

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What does your other head say? I have a set of 1970 #12's that were cast in Sept. 1969. when I bought them in 1984, the "12" could easily be read on both heads. Now, the driver's side head is just like yours....illegible. Heat, rust, and age sometimes erode the numbers. I'd bet yours is an original #12 head.
 

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WT is a block code, not a head code. It is for a 4 speed 400 engine. All indications are that you have an original engine and its original heads. Don't worry....be happy.
 

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Year model 1970 --- there should be another 4 character date code on top of the block, back near the distributor. This one can be hard to see with everything installed. It should be numerically "close" to the head codes. Since that first digit is a 1 on your heads and we now know they're 70's, then the only possibilities are 11, 12, 13, 15, or 16. You might try light sanding on that second digit with some sandpaper to see if that second digit will pop out at you.

Bear
 
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