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Main : Mechanical : Engine A12A Cylinder Head ports

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A12A Cylinder Head ports
A12A Cylinder Head portsPopular
SubmitterddgonzalMore Photos from ddgonzal   Last Update2005/6/14 7:02    Tell a friendTell a friend
Hits5498  Comments6    0.00 (0 votes)0.00 (0 votes)
1981 A12A engine (1237 cc)
marked H95 (shrouded oval ports)

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

Poster Thread
Dodgeman
Posted: 2005/6/15 3:26  Updated: 2005/6/15 3:26
No life (a.k.a. DattoMaster)
Joined: 2003/6/27
From: Southern Tablelands N.S.W. Australia
Posts: 8287
 Re: A12A Cylinder Head ports
Oh krepp, it looks like a perfectly good head that has been ruined,.... by design. That lovely oval port seems to be reduced to half its cross section right at the valve stem.

A12A owners,... i feel your pain.

Poster Thread
L18_B110
Posted: 2005/6/15 3:48  Updated: 2005/6/15 3:48
No life (a.k.a. DattoMaster)
Joined: 2002/8/6
From: Brisbane, Australia
Posts: 3792
 Re: A12A Cylinder Head ports
they could upgrade to the round port head! :lol
that's bloody horrible

Poster Thread
pro-240c
Posted: 2005/6/15 3:57  Updated: 2005/6/15 3:57
Home away from home
Joined: 2004/3/3
From: WA
Posts: 957
 Re: A12A Cylinder Head ports
for the amount of good that porting would do, you might as well weld a sharp bit of metal to the top of the piston to reduce detonation

that really is awful. why not just use an A14 oval port head....?

Poster Thread
ddgonzal
Posted: 2005/6/15 8:08  Updated: 2005/6/15 8:08
Moderator
Joined: 2001/5/3
From: Kent, WA
Posts: 31735
 Re: A12A Cylinder Head ports
Quote:
why not just use an A14 oval port head....?
Because the A14 models didn't get 47 miles per gallon. The A12A did. The protrusion in the port was to cause the air/fuel mixture to swirl as it went into the combustion chamber, promoting a more efficient burn (better fuel economy). It reduced emissions too I think.

I would guess that at low speeds, this head makes more power than the unshrouded A14 oval port head. Of course at high speed, the obstruction in the port is not so good.

Poster Thread
pro-240c
Posted: 2005/6/15 8:18  Updated: 2005/6/15 8:18
Home away from home
Joined: 2004/3/3
From: WA
Posts: 957
 Re: A12A Cylinder Head ports
looks more like it would hinder swirl than aid it.

Poster Thread
ddgonzal
Posted: 2005/7/2 5:00  Updated: 2005/7/2 5:00
Moderator
Joined: 2001/5/3
From: Kent, WA
Posts: 31735
 Re: A12A Cylinder Head ports
Quote:
ooks more like it would hinder swirl than aid it.
Does look like it, eh? But scientifically proven to aid combustion (although of course a hindrance to high-rpm flow).

Also used by GM, Chrylser, BMW, Mercedes, etc.

For comparison:


Tech article: GM V8 swirl portQuote:
works well to swirl the air/fuel mixture, increasing low-speed torque and fuel economy ... not particularly suited for producing horsepower in the upper rpm range.
The GM port restriction from the side looks very similar to our A12A photo (Large photo of GM port can be seen at http://www.sallee-chevrolet.com

Poster Thread
ddgonzal
Posted: 2005/6/14 7:01  Updated: 2005/6/14 7:01
Moderator
Joined: 2001/5/3
From: Kent, WA
Posts: 31735
 Re: A12A Cylinder Head ports
Under cylinders 1 & 2 there is only one water hole. But under 3 & 4 there are two holes.