Stromberg 175 CD2 rebuild

[Guest]

Hi, I'm new to site & currently rebuilding above carbs, I have a question that I hope someone can help me with.
What is the spring loaded valve on the throttle butterfly? my rebuild kit has new butterflies that do not have this valve fitted, is it actually needed?
cheers.

[StagnJag]

Hi Paul and welcome to the forum.

I think I can answer this!

They are commonly referred to as poppit valves. I believe the theory is that they release some of the vacuum from the cylinders and help to prevent oil being drawn up past the rings. In practice I don't think they really make any difference. I seem to recall being told that they can also be the cause of 'popping' in the exhaust on the over run. Mine does this and I was considering replacing the butterflies with the plain ones that I've got. It isn't high on my to-do list though!

Rgds

Dave

[milothedog]

Hi, I'm new to site & currently rebuilding above carbs, I have a question that I hope someone can help me with.
What is the spring loaded valve on the throttle butterfly? my rebuild kit has new butterflies that do not have this valve fitted, is it actually needed?
cheers.

They were put in to stop exhaust popping on overrun, they tend to get taken out and the hole filled so your safe to just fit the ones in your kit.

Ian

[Stagdad]

Welcome neighbour.
I think it was to stop over lean popping on overrun,I swapped for the plain disks that came with the kit on advise from the forum when I did mine.Alan (157.7)will know the definitive answer.

cheers Steve

Ian and Dave type faster than me

[StagnJag]

Lol, the opposite to what I said then!!

My popping must be something else.

[martin]

lol, the opposite to what i said then!!

My popping must be something else.

beans ?

[Guest]

Cheers guys, I'll steam on then.

[StagnJag]

More than likely!

[Arbman Al]

Cheers guys, I'll steam on then.

Hi Paul

I'm only down the road from you in West End if you need to look at a stag for reference, or help.

Cheers...Al

[stag157.7]

use the earlier plain throttle discs
the poppet valve
was designed to open under conditions of high manifold vacuum, as in engine braking and over-run, when excess fuel tends to be sucked out of the carbs. The open poppet valve allowed more air to be drawn into the engine, which helped burn off the extra fuel and reduced the CO emission levels.

trouble is they did not work to well and opened when they are not supposed to allowing more air in at idle and upsetting the mixture



alan