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New A series oval port head
No life (a.k.a. DattoMaster)
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Posted on: 2003/2/16 14:46
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Re: New A series oval port head
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The starting bid is a great price.

The 1979 A14 and A15 "210" (B310) use the same head. For those of you not too sure what you have note that the oval looks almost round. But it's definitely not perfectly round as in the A12.

The seller says it's p/n 11041-H7763, and marked on the head 107 and H72. Originally, the 79 heads had part number 11041-H7702 (49-state) and 11041-H9162 (California), but part numbers sometimes are superceded with a new number.

Posted on: 2003/2/16 18:02
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Re: New A series oval port head
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That's open chamber anti-pollution head, at stock form it's even worse than small-port closed-chamber head. Those Open-chamber heads absolutely kill engine performance, they aren't suitable for turbo use either as they make engine to detonate much easier than real wedge heads with same compression ratio. That open chamber head can be made pretty good by milling but factory closed-chamber heads are still more suitable for performance use.

Posted on: 2003/2/16 22:53
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Re: New A series oval port head
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naukkis, I hear what you're saying about using these heads in a high-compression engine ... but not sure why these wouldn't make a good low/mid compression engine. Some of us would prefer a 8.5/9.0:1 engine for the street rather than racing. At this compression using these "anti-smog" heads, our least expensive gasoline doesn't ping (use a 180 degree thermostat).

Can you elaborate on why the open chamber is bad?

I've heard that the air-injection bosses can be ground down in the ports. Most of the US A14 heads are air-pump heads, except I think for the 1975 non-California heads, so these are what most of us have used.

The valves in all A14 heads are inclined, making it a wedge-head (?) except for the large volume below the valves, which as you point out can be milled off. It's still open chamber though, if I understand correctly open chamber means the area around the valves is more flat and "open". The open-chamber design I thought was good for airflow, and using popup pistons to raise compression was superior to closed chamber.

Closed chamber has metal surrounding the valves on the high side of the wedge resulting in a heart-shape combustion chamber. This raises compression and "quench" (movement of the compressed mixture) for more power but high emissions. Newer engines use "swirl" tech for power and low emissions (with varying success) but I'm not sure exactly how that works.

Posted on: 2003/2/17 1:10
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Re: New A series oval port head
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Quote:

ddgonzal wrote:
naukkis, I hear what you're saying about using these heads in a high-compression engine ... but not sure why these wouldn't make a good low/mid compression engine. Some of us would prefer a 8.5/9.0:1 engine for the street rather than racing. At this compression using these "anti-smog" heads, our least expensive gasoline doesn't ping (use a 180 degree thermostat).


Yeah, it won't ping but either it won't produce power and also has bad fuel economy.

Quote:

Can you elaborate on why the open chamber is bad?


Because it's ruined head design just for emissions.

Quote:

The valves in all A14 heads are inclined, making it a wedge-head (?) except for the large volume below the valves, which as you point out can be milled off. It's still open chamber though, if I understand correctly open chamber means the area around the valves is more flat and "open". The open-chamber design I thought was good for airflow, and using popup pistons to raise compression was superior to closed chamber.


No, closed chamber just means that chamber is closed eg some part of chamber is at same level as head sealing and upcoming piston closes the chamber so it becomes smaller rapidly. That squish area is the reason for wedge-head and when tuning you want to make piston to come as close as possible to those squish-areas( and make those squish-areas as large as possible without sacrifacing flow). That open-chamber head makes just opposite, real anti-tuning to engine and that so stupid that you have to wonder why Nissan ever made those.

Here's some link.
http://www.chevyhiperformance.com/techarticles/94138/

Posted on: 2003/2/19 0:54
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Re: New A series oval port head
No life (a.k.a. DattoMaster)
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Isit possible for someone to put up the casting numbers for the best high comp oval head to work on somewhere on the tech info page??

Posted on: 2003/2/28 3:26
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Re: New A series oval port head
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yes, I can add it to the Tech Section. I can either put it in the "best engine" article, or finish the draft of that "a-series engine mods" article I started.

The only problem is ... what are the casting numbers? Or what years/models have the "good" heads?

Posted on: 2003/2/28 7:24
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