porous plug

jimlb · Aug 30, 2017

What part does the porous plug play in a marvel carburator?

TBN Support · Aug 31, 2017

:welcome:

Welcome to the forum!

I'm going to move this thread over to our parts and repairs section to see if we can get you an answer.

rScotty · Aug 31, 2017

jimlb said:
What part does the porous plug play in a marvel carburator?

Gosh, it's been decades since I've rebuilt a Marvel-Schebler....but they are wonderful carbs. So simple and rugged & respond well to basic cleaning and adjusting. Plus everything in the design - except for that oddball porous plug - makes perfect physical sense. Here's a link to a good tutorial manual:
http://www.oldcarmanualproject.com/manuals/Carbs/Marvel-Schebler/MS-DLTX-TSX.pdf

I'm assuming you are asking about that odd sintered metal plug made of kind of a brassy material? I've done lots and lots of Marvel-Schebler rebuilds and I've seen that sintered metal plug in two places. Sometimes on the bottom on the carb float bowl where it makes no sense at all to me and looks like it ought to leak...but it doesn't.
And I've seen it in the wall of the carb up above the float bowl overflow above the liquid level.... up there where it could at least serve as a fluid-restricting vent.

In both locations, the sintered metal plugs like they were installed at the factory by some sort of staking or stamping process that deform the surface of the surrounding metal just enough to hold the sintered plug tightly in place....That installation method itself sure looks like it is intended to be permanent, and is enough to give the thinking mechanic pause when considering replacing the sintered plug.

Frankly, I've never replaced those plugs. And I've never found them to affect the functioning of the carb. Some Marvel Carb kits include the plugs and others don't. So what I've done is to just clean the surface of the plug well with gasoline and a soft brass brush and then use compressed air lightly against the inner face of the plug to force out any remaining gasoline and/or carb cleaner that might be trapped in the sintered metal Other than that rather cursory treatment I just let them be.

As I said, I like that carb and the way it works and how well it responds to adjustments. And I'm completely mystified by the function of that plug. But that's OK, after all...how often in these days of aluminum and plastics do we get to encounter something as archaically satifying as a carburetor made of cast iron? What's next...stone wheels?

And if anyone does know something of the mechanical history of that sintered plug ..... especially the one that is sometimes staked into the bottom of the float bowl next to the drain plug.... please enlighten us.
rScotty