I could have used the manifolds from the
2.5PI set-up. The main reasons I didn’t
were:
Too mean to buy a set (sad isn’t it), especially when I was
going to have to modify them anyway.
If you want to use the airbox that goes with it, you have to
put a bulge in the bonnet.
The throttle linkage is a bit of a pain
A single throttle body plenum type arrangement would be
easier to supercharge in the future.
So I decided to make one. I once worked as a fabricator but my garage
is much less well equipped than a fab shop.
This is why it took more time and effort than I had originally expected!
The components laid out. The flanges were particularly time consuming
being made from 10mm plate!
I wanted the runners as long as possible
(in the hope of keeping the torque up).
They are offset forward to keep the plenum clear of the clutch
master. I over-did it a bit and was
short of space at the front as a result.
The plenum is rectangular as I wanted to
be able to smooth the entrance to the runners after I welded them in.
Tacking it all together. The spare head was an essential part of the
process.
Fitting the injector bosses.
I wanted these as close to the head as
possible squirting onto the back of the inlet valve. Didn’t quite achieve this – but close.
Inside the plenum. Corners were radiused to help airflow into
the runners. The angled runners should
help too,
The brownish blob bottom left is the tip
of the inlet air temperature sensor mounted so that is just in the edge of the
airflow. In practice heat soak is a bit of a problem.
Almost finished - the underside of the
manifold. Note the throttle cable
guides and stubs for breather/extra air valve plus a spare in case I ever want
a brake servo. You can also see the
outside of the inlet air temperature sensor.
In case you were wondering, in this
picture the throttle body does have an idle solenoid on it. As it turned out it didn’t work
(Lucas)! Therefore it got cut off and
the holes left were plugged.