Single 1 3/4 manifold

[Morris]

I want to use a single 1 3/4" SU on my 1500 engine. I know of the Herald manifold with the "swept" type of runners but have also seen reference to using the Dolomite manifold. Are they different and if so, which is best (fight!).

I know I will have to modify for the carb, not a problem.

 

Thanks.

[Mother Teresa]

Is that for economy reasons, going for 1 carb? John Thomason carried out a 2vs. 1 carb experiment some years ago in the TSSC magazine- do you have access to that ?

[Morris]

Is that for economy reasons, going for 1 carb? John Thomason carried out a 2vs. 1 carb experiment some years ago in the TSSC magazine- do you have access to that ?

It saves me having to move my master cylinders plus simplicity.

A single 1 3/4 supports just over 100 bhp on big A series engines, I can't see the Triumph being any different (I'm only aiming at 80 ish).

 

[akumanospitfire]

AFAIK there's no 1-3/4 single manifold for the Triumph 4 cylinders, only the 1-1/2 version.

However I don't recommend using it; the Triumph single carb manifold has very, very small, inlet ports and some horrible 90degree bends giving poor performance.

80hp is not possible with that horrible intake, the 1500 US spits were rated at 53HP SAE with it.

There's not enough meat in them to make the ports much bigger either.

 

Stick to twin's or run a downdraft Weber if you absolutely must have a single carb, or fabricate your own manifold.

 

 

A.

[clshore]

AFAIK, there are two versions of the single carb manifold, one has tiny 1" runners, the other has 1-1/4" runners, same size as the inlet port.

The tiny port version increased charge velocity at lower RPM, which helped cylinder filling, and boosted torque. Of course, it sucked at higher RPM.

[Morris]

Thanks for the input guys.

I have found that, as said, there are two totally different manifolds. The one I am looking for is the Dolomite one, which has the large ports and nice swept runners. They are also hard to find.

 

As Akumanospitfire suggests, I can see another fab job looming.

[Nick Jones]

I think there was a 1.75" manifold used on the early 1500 Dolomite of 1500 FWD.  The 1.5" was also used.  TBH, I doubt you'll notice much difference going from 1.5" to 1.75"

 

Nick