marvel schebler venturi

175 venturi is one inch. Call an AGCO dealer to see if it is still available or not.

Part number from AGCO is 70251715 for the venturi. There is also a retainer 70251726 that I've never used, just the venturi.

Well Im going to have to do what you suggested wi50! Local Agco dealer said the venturi is obsolete and can not get one. Oh well, custom should have its upsides! 

That's the problem with the one I have. Its wrapped and has a tiny crack in it. So if I was to replace it I would just go bigger.

I have found what I think is the keerect plastic venturi. McDonald Carb & Ignition  706-367-4179    Jefferson, Georgia.........p/n  46-A248.....1 inch I.D. venturi for 1 3/16" throttle bore TSX Marvel-Schebler carb   $25 bucks.      Can't make the venturi any longer without changing the internal machining of the carb body.

If one was to be custom made, I would machine out the body of the upper half just a bit and then maybe try and machine upwards about 3/16 of an inch

Be nice to really know if either of them are really 1 inch diameter or the smaller 7/8 inch or even less than that.

About a year ago someone here was asking about what carb to run on a WC. We covered the subject and "your boss" (yeah right) buchard thought that you could pull air through a carbuerator venturi at the speed of sound...... so I wouldn't think carb advice from him could be much of any real world value to those looking to learn. Sounds like you boys are still sore from running into Rockin Rodney Bender.

Anyways John Deere used a Marvel carb, I've got plastic venturi from the 6600 combine was about the largest HP application for that carb. Weather or not it's available through Deere I have no idea, I don't even remember the diameter weather it was 1" or larger.

On the subject of making one yourself, just pay attention and get the smallest point of the venturi positioned properly around the end of the fuel nozzle. You won't have to machine your carb body at all to make a longer venturi to blend into the bottom bowl. You can turn the outside diameter to fit down into the carb bowl. I'll take some time one of these days and take some pictures so you can see what I'm referring to.

Buying one is the easy way to do it, but you can make one easy enough and if you make it properly you'll find a big gain in the airflow capacity of the carb. For example when doing the tests that I refrenced to above and swapping out several venturis it wasn't hard to find another 30 CFM of air through a custom made ventrui in some tests that was the same size as a OEM one. It's all in the approach that the air has to the venturi.

Like I've posted before every orfice (in this case the venturi) has a coefficient of flow, every inlet and exit to that orfice has a flow coefficient. For example if you drilled a hole (approx. 1.18" diameter) with 1 square inch of area in a plate and bolted it to the flowbench and pulled a test at a set depression it would flow just say 85 cfm. Take that same plate and radius the inlet, it'll flow more, radius the outlet (bottom side) and it will flow more yet. Put a long tube on it leading up to the orfice, change some radiuses and you keep finding gains.

A venturi is a very well shaped orfice, unfortunately the area leading up to the venturi is not well shaped, and these factory ones have a fairley blunt bottom end.



I spent to much time last year explaining this to pankey, but if you search for that thread I posted how to figure the size of the venturi needed depending on your engine specifics. Of course a larger venturi will take more "signal" from the cylinder to make it work. Once the signal gets to weak the engine will fall on it's face. By making it and sizing it properly you'll have the added airflow of a large venturi in a carb that will work optimum in a wider RPM range.

The carb I have is a TSX 871, is that a descent enough sized carb?