These are air flow numbers measured on a flow bench.
The later head looks like it should be much better than the early one but in
reality the biggest issue is small valves and poor combustion chamber shape,
not the actual gallery. The only place where the stock BN4 head outflows the
later one is at very low lift and this is due to having 30 degree valve seats
which have a larger curtain area than the later 45 degree ones. This makes no
real world difference in horsepower though.
Andy.
--------------------------------------------
On Mon, 7/9/15, Wilko2 <e-wilkins@cox.net> wrote:
Subject: Re: [Healeys] Longbridge head modifications
To:
Cc: healeys@autox.team.net
Received: Monday, 7 September, 2015, 5:17 AM
Are these numbers theoretical, or
from actual dyno?
I'm very curious about how that design could out-perform the
later design.
Wilko
On Sep 6, 2015, at 1:05 AM, Andy Thorp wrote:
> Since it is a bit quiet, here's something I've been
playing with over the (southern hemisphere) winter. I was
always interested in just how "bad" the Longbridge gallery
head was given that it is pretty much the same layout as the
later ones with two carbs and a log manifold channeling air
through a series of abrupt 90 degree bends. The biggest
improvement in the later head is the bigger valves, and when
these are fitted to the gallery head with chambers and ports
relieved accordingly, the air flow rises to above the stock
3000 setup. The exhaust is a little different though- the
3000 exhaust valve is too big and reduces flow due to
bore/block shrouding. Hoping for 125hp from an otherwise
stock Longbridge engine this summer once it is all back
together.
>
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