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In 1998 I bought a Triumph Herald 13/60, here you can read about it's restoration and share in a few photo's from it's travels. Please feel free to leave comments to any of the posts, of even email me if you want to.

Monday, February 13, 2017

Converting a Triumph Herald to EFI (Part 2 - Fabricating the Inlet Manifold)

I decided to make the inlet manifold from mild steel, as it was the easiest material for me to work with as I had access to a MIG welder. It was also cheap, I bought enough steel to make several manifolds for around £40. It uses a single throttle body and injectors from a Rover 25, these were chosen as they are used on engines of similar size and slightly above the bhp achievable on relatively standard 1296cc Triumph engine.

The construction of the manifold is a pair of flanges, 4 runners, single plenum and adapter plate for the throttle body. I was struggling to find someone to make the flanges and adapter plate for me, but a local TSSC Devon member who had a lathe came to the rescue.

Cylinder head flanges and runners
The first stage was to clamp the flanges to a spare cylinder head, then tack weld the 4 runners keeping them at 90° to the flanges and parallel. Then offer up the plenum to the other end of the runners, mark and cut the 4 holes needed and then tack into place.

Flanges, runners & plenum tacked in place.
Once I was happy everything was where it should be it was fully welded. Then the end plate, reducer and throttle body adapter plate were all welded on. Next was to add 2 bungs for vacuum connections for the MAP sensor and fuel pressure regulator, mounting and inlet tube for the idle control valve, a guide for the throttle cable, mounting plate for the fuel rail and finally the 4 injector bungs.

Top side of the inlet manifold
Underside of the inlet manifold
Inlet manifold painted and in place.
I wanted the runners as long as possible, so the plenum was just inside the inner wheel arch. The engine side valance had to be modified to allow it to project that far and for the throttle body be just to the right of the radiator.

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