How to remove the plenum trumpets.

[mk1fan]

Going to shorten my trumpets. How do I get them off the base? Gentle tap to the side with a hammer? Drift out from the underside.

[Wedg1e]

Put the assembly in the oven at 100 degrees or so for an hour, the alloy base will expand and let you wiggle the trumpets out. Most you should have to do is tap them around a bit, you can't easily drift them out as the base is stepped.
It's debatable whether shortening the trumpets has any effect without serious additional mods., mind you.

[Number 7]

Shortening them will tend to move peak power revs upwards - unless you're going to compensate with a spacer under the base. John Eales used to do an exchange base with his 45mm shortened flared alloy trumpets (standard are 38mm) but then you'd need to open out the inlet manifold to match the larger trumpet ports.

[Brithunter]

Your standing on the edge of a very slippery slope .............................................. so careful! One little step is all it takes to begin the descent into serious modding and tuning One on the way down it is almost impossible to get back up to the top once more!!!

Known in some circle as "The dark Side" ..................................... have fun

[adam quantrill]

Mine remove themselves...

[billynobrakes]

mk1fan said:

Going to shorten my trumpets. How do I get them off the base? Gentle tap to the side with a hammer? Drift out from the underside.

The route you are taking so far with bigger brakes, vented bonnet etc why not just buy a bigger engine and have done with it

[TV8]

billynobrakes said:

The route you are taking so far with bigger brakes, vented bonnet etc why not just buy a bigger engine and have done with it

knowing Stewart, he will probably do that as well!

[adam quantrill]

in that case the answer would be:

To remove the plenum trumpets, first remove the engine, then put a bigger engine in.

[mk1fan]

3.5 is fine. Got a thermal gasket coming with the manifolds so would like to keep things 'even'. Plus, moving the centre trumpets away from the underside of the plenum top is an easy bonus.

[Wedg1e]

mk1fan said:

3.5 is fine. Got a thermal gasket coming with the manifolds so would like to keep things 'even'. Plus, moving the centre trumpets away from the underside of the plenum top is an easy bonus.

Depending on the insulator thickness it can also move the plenum chamber rather closer to the bonnet than you might expect.
My car has a 10mm insulator but I milled 10mm off the bottom of the trumpet base to compensate.
Shortened trumpets, couldn't tell any difference... but you can place your hand flat on the plenum after a good thrash and it's merely very warm rather than too hot to touch.