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1973 Cylinder Head
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Buddy of mine picked up a 1973 1200 car. He says it has original early A12 engine with 4 speed. Plans to pull both engine and gearbox out and no use for it. Cylinder head has no markings. Any idea if this is open or closed chamber, round or oval ports? Can't tell if it has double valve springs from pictures. He said manufacture date is mid 1973.

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Posted on: 9/9 3:35
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Re: 1973 Cylinder Head
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Good questions

* In USA, orginal A12 (1970-1973) was the only A12 ever sold in this country

* Only the 1971 came with closed chambers

* Dual valve springs were not used in USA, but certainly could have been purchased from Datsun Competition and installed. A photo from the side will tell

* Unmarked head is either A12 or A12GX. I see a carburetor peeking out of the edge of the photo with the 1973-or-later anti-diesel valve. It appears to have all the stock 1972/1973 emissions gear

Posted on: 9/9 3:55
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Re: 1973 Cylinder Head
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Thanks DD. So then this would be an open chamber meaning lower compression? And does it have round or oval ports? I have seen the GX heads with the "Japan Nissan" stamp. Some GX heads do not have this writing?

Posted on: 9/9 4:36
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Re: 1973 Cylinder Head
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Open chamber does not mean low compression. With the A-series engine, the compression is mainly due to the piston dish (3 different pistons were used on B110s)

29cc A12GX head
31cc A12T GX head
28cc A12 Closed chamber

Compare to 30cc H89 Closed chamber

9.0:1 1971 North America (69 hp)
8.5:1 1972-1973 North America (68 hp)

1972-1973 north america used open chamber with a deeper dish piston

Closed chamber is more efficient, more resistant to detonation. It's good for 1 hp on regular gasoline, and 3hp with flattop pistonz and premium unleaded. But closed chambers also creates more NOx pollution which is why it was changed to open chamber

All A12 heads are round-port -- except A12GX and A12T. I believe all GX heads are cast with "JAPAN" and "NISSAN" on the top of the head
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This is the open chamber 1972-1973 head
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Posted on: 9/9 10:40
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Re: 1973 Cylinder Head
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Appreciate the info DD. So in 1974, the A13 was introduced and later years with the A14 and A15. This particular engine is an early A12, dizzy below #1 plug. What years and what vehicles came with the late A12 engine? I am familiar with the A12A that was offered in the 210 beginning in 1978.

Posted on: 9/9 15:43
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Re: 1973 Cylinder Head
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Late A12 engine came in non-USA B210, Vanette, B310 Van, Cherry, F10

Posted on: 9/9 20:36
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