Hi Steven,
I'm doing a little exercise on the early BN4 gallery head to see just how
"bad" it was compared to the later DMH designed one, and some of the things I
have discovered are very applicable to the four cylinder engine too.
Despite the horrible intake gallery design of the early six cylinder head, it
actually flows no different to the later 3000 one when put on a flow bench.
The reason for this is because the majority of restriction to flow is the
inlet valve and combustion chamber area, rather than the actual intake tract.
The later head has bigger valves which for the intake gives better flow at
higher lift, and when a later intake valve is installed in the gallery head
plus grinding out metal around the valve, similar results are obtained to the
3000. The exhaust is marginally worse on the 3000 head than the early one
because the exhaust valves are bigger and get in the way of the flow out of
the combustion chamber. Attached are a couple of graphs comparing intake and
exhaust flow of the gallery head and stock 3000 head.
So, to reiterate the well worn advice of anyone who has used a flow bench-
power comes from air flow and air flow comes from good shape around the valves
and into the chamber. Carbs and intake ports only make a difference if they
are the biggest restriction, and in the case of the Healey engine they are
not. You will make good power from a stock head with some time spent on
improving the air flow around the valves, plus raising the compression ratio
to a sensible level.
Andy.
--------------------------------------------
On Sat, 6/12/14, Steven Kingsbury <airtightproductions@icloud.com> wrote:
Subject: [Healeys] Increased Horsepower
To: healeys@autox.team.net
Received: Saturday, 6 December, 2014, 6:38 AM
A short while ago, some listers were
talking about getting increased
horsepower in their AH 100's by just changing over to an
alloy head with
better breathing. Keeping stock carbs and still getting a
great increase. Does
anyone have any documentation as to the actual increase? The
reason I ask is
that I have a friend with another 100 and he's thinking of
going with full M
mods, (Cold air box, bigger 1-3/4" carbs, new manifold, new
cam, valve
springs, etc.) and keeping his iron head. I told him about
the talk here about
the alloy head and before he jumps in to the rebuild, I'd
like to pass along
some information before he gets too far in to his project.
Thank you all in
advance for your information.
Steven Kingsbury
BN1 #598o;?
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[demime 1.01d removed an attachment of type image/png which had a name of
intake air flow.PNG]
[demime 1.01d removed an attachment of type image/png which had a name of
Exhaust air flow.PNG]
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