zeinith vs. marvel carbs

Both are good Carburetors. They both mess up though with dirt and debris. To me being I rebuild both quite often for customers. I sorta' like the M/S Carbs a little better mainly because of the larger float bowl area in the small bore and the large bore. Sparky made a good point about the Zeniths being a little finicky when it comes to fine tuning them. Whenever you rebuild either Carburetor, one thing you have to concentrate on is the inlet cavity. A lot of rust, dirt and debris gets lodged in those cavities and over the years the rust starts to break off out of the threads where the elbow screws in and man does that play havoc with the Viton needles. The Viton needles are great for sealing good, but it you get minute pieces of rust dislodging in that inlet cavity, it sticks to that Viton needle like glue! Next thing you know fuel is runnin' out everywhere.  Both Carbs have their little "quirks" but as long as you can get em' super clean inside, make sure the floats aren't swiping against the inside float bowl walls, both Carbs perform quite well.

When it comes to pulling Tractors, personally, I think you can do a lot of improvements on the Marvels as far as smoothing out the intake bore and small changes with the venturi and increase air speed on both the small and large bore units. The small bore Zeniths I think are a little more restrictive to what you can do, but the large bore Zeniths seem to perform quite well with some mods. Like anything else, it's preference. JMHO.

Steve@B&B

 

The old chap who told it to me was the kind of guy who'd speak about his own wacky theories as if they were fact. But I got thinking about it the other day when someone on another forum posted about carb icing issues on their Oliver 1655. The 1650's, 1655's, and 2-70's all had bad carb icing problems - so much so that Oliver developed a service bulletin with a re-worked intake for that could be changed to draw hot air from around the exhaust. Even today, lots of folks post about the carb icing problem on those tractors. Those Ollies/Whites used 265 cu in., 6 cylinder engines and were about 65 HP. The Allis 180 also had a 265 cu. in. 6 cylinder engine producing the same HP, and I've never heard of any carb icing problems on them, nor have I ever had any issues with my 180 gas (nor the 190, with the same engine). The only difference I can think of from a carb-icing standpoint is the M/S vs. Zenith carbs.

Maybe the zinc bowls of the Zenith's made a difference, compared to the cast iron bowls of the M/S? Zinc is over twice as thermally conductive as steel/cast, so maybe it helped absorb some heat from the engine/surroundings better.