Chris,
I just happen to have one of the AEC 960 heads with the "deep" recess you
cite. What I see is that the electrode is flush with the "roof" of the
chamber and the more or less heart shaped design has a slightly notched
(less girth) adjacent to each exhaust valve. I presume this initiates a
swirl like action as the mixture is compressed. I have no earthly idea which
direction it swirls, but I can only surmise that it approaches the electrode
tip from the intake side (right to left). This would probably benefit from
plug indexing.
In other words, I'm still at a loss over whether your modification is
adding performance, which you haven't said much about. I'll continue to
investigate.
dave
_____
From: Chris Dimmock [mailto:austin.healey@gmail.com]
Hi Dave,
No - once we discovered the issue - which was during the rebuild - we just
fixed the problem by machining the plug seats.
It is clearly a factory machining issue.
I'm hoping some other listers may have a 12 port head they can check. I'm
sure that not every Aec960 casting was machined wrongly. After all - they
got the machining on the 6 and 12 port 100/6 heads right, and the a series
heads, and the b series heads.......
Best
Chris
On 06/10/2010, at 12:15 AM, "Dave Porter" <frogeye@porterscustom.com> wrote:
Chris,
This is interesting. I can't imagine who to ask about the behavior of flame
fronts vis a vie compressed versus non-compressed gases.
I was surprised last week when I added up the advance numbers for the BJ8
and it was like 47 degrees total, but there must be an explanation for it
when all of the other parameters among the distributer models are so
similar.
Just out of curiosity, did you experiment with long reach plugs or hogging
out the combustion chamber to achieve a flush insertion as well? I will be
discussing this with some other folks and need to cover the bases..
Thanks!
Dave
_____
Ok Guys - here is the follow up as promised re the spark plug seat issue on
the AEC960 cylinder head.
I've discussed this on and off for nearly 12 years - we discovered this
issue when I rebuilt my BJ8 in 1998
Yesterday, I pulled out 3 different westlake design cylinder heads - a
Sprite; a 100/4; and a 3000 - and using the SAME spark plug - took a few
pics....
Simply - the spark plugs on "some" 12 port 3000 cylinder heads don't go in
deep enough compared to any other westlake head design.
Which is just wrong....
Here is my take, with pictures....
<http://www.myaustinhealey.com/aec960-healey-cylinder-head.html>
http://www.myaustinhealey.com/aec960-healey-cylinder-head.html
Fire away.....
Chris
<http://www.myaustinhealey.com>
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