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Main : Mechanical : Engine A Series Head comparison

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A Series Head comparison
A Series Head comparisonPopular
SubmitterFandatstickMore Photos from Fandatstick   Last Update2009/10/19 11:27    Tell a friendTell a friend
Hits3222  Comments5    0.00 (0 votes)0.00 (0 votes)
Head comparison.

mm A12 GX    H89 (A14/A15) A12 Round Port
Inlet port 39 X 30    35 X 29        27.5 X 26
Exhaust port 28 X 26    28 X 26        27 X 26
Inlet valves 35    37        35
Exhaust valves 29    30        29
Combustion
chamber depth 13    8*        10
Comments *H89 Head has been planed.  
Others are Unmolested.

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The comments are owned by the poster. We aren't responsible for their content.

Poster Thread
ddgonzal
Posted: 2009/10/24 18:30  Updated: 2009/10/24 18:30
Moderator
Joined: 2001/5/3
From: Gone to Maui
Posts: 31391
 Re: A Series Head comparison
Looks like an A12T cylinder head, instead of a GX head:


Oil Passage Comparo

Notice the one labeled GX doesn't have the oil passage on the head face, instead there is a white area where the gasket had a hole for the oil passage.

Poster Thread
Fandatstick
Posted: 2009/10/25 10:28  Updated: 2009/10/25 10:37
Home away from home
Joined: 2003/10/23
From: NZ
Posts: 282
 Re: A Series Head comparison
DD - what other differences do you think there are between GX and "A12T"? To my eye it's just a later version GX head.

The engine it comes off is mid dizzy A12 and had twin "SUs" (which I promptly sold a week after buying the engine as I was after the head. Got more for the carbs+inlet man than I paid for the whole lot. The guy who bought them was putting a Datsun A series into a 'Spridget' and wanted the engine to look vaguely 'British').

I have another GX head on my race-engine. Looks identical except it has the oil feed hole (as per early engines).

Poster Thread
ddgonzal
Posted: 2009/10/26 1:27  Updated: 2009/10/26 1:27
Moderator
Joined: 2001/5/3
From: Gone to Maui
Posts: 31391
 Re: A Series Head comparison
Quote:
mid dizzy A12
Right, Datsun 1200 GX engine was front distributor, so your engine was the A12T. Mid-distributor engine don't have the extra oil passage in the cylinder heads.

All these Datsun engines came with twin Hitachi sidedraught, hence the 'T' in A12T. SUs were not used. Hitachi design is probably a licensed version of the SU carburetor technology, or perhaps the patent expired. Anyways the Hitachis are very reliable so any bad things you hear about SUs don't apply.

A12T head was used by B210 and E10 (Cherry) and is similar to the A12 GX head. Similar ports sizes, same valves sizes, dual-valve springs. Ports may have a slightly different measurement. By contrast, the A14T has small ovals, same size as regular A14 head.

The A12T head appears to be every bit as good as the A12GX head, except you cannot just bolt it on an ealry engine. You can bolt the GX head on both old and new engines.

Poster Thread
Fandatstick
Posted: 2009/10/26 10:19  Updated: 2009/10/26 10:19
Home away from home
Joined: 2003/10/23
From: NZ
Posts: 282
 Re: A Series Head comparison
Thanks DD. Sounds like an 'A12T' Head is just a later model A12 'GX' Head (ie only difference being that it doesn't have the oil feed drilling).