Carter RBS and the Pony Carb

I was just reading through the "Selecting the Right Carburetor" tech article and was really focused on the section with the 1bbl carbs. I know the RBS is as big a one barrel we will ever get and the Pony is a great carb as well with it's extra features. IIRC the RBS flows 215 and the Pony according to that article flows around 200.

Would it be possible to build a mild six using either one of these carbs? I'm talking about maybe a 110-130HP mild build. Or would it be too much for these carbs?

Howdy Ralf:

It is possible to build an engine and under carb it. In general, RPM goes up, more CFM is needed to support it. 215 cfm is quite a lot of carb for a mild, street 200. Yes, it is possible to overbuild and under carb an engine. But, that's probably a more liveable scenario than under building the engine and over carbing it. I will crank up the CR calculator and run some numbers with 215 CFM as the constant and see what we get. I'll be back.

Adios, David

I have a stock 200 ('78 block and '80 head) with an RBS on it and it doesn't seem to be too much. In fact it runs better than any other carb I tried. The RBS came stock on early Mustangs with 250 engines.

I learn something new everyday. I'd figured from all that I have read on this great site that if someone were to upgrade the cam to a nice mild one you would have to upgrade the 1v carb to a 2v to take advantage. If indeed 215 from a single carb is too much, that's new info to me. Even though it does flow 215, does it do it constantly though? I mean, is it worth it having it there on a refreshened head that has had some work done on it besides a 2v conversion? You know, something like 3 angle valve job, some porting work and rockers?

But anyway, good info to know.

I have a fully ported head, 264/274 cam, and the stock 1bbl Holley 1946. It rocks, but it seems like the cam is capable of using more carb at high rpms. Unless you plan to spend a lot of time at 5000+rpm then I wouldn't worry too much about not having enough carburetion.
I was a little afraid of being lean with this carb so I did put in a larger jet. I don't have any way to check A/F ratio.

I was a little afraid of being lean with this carb so I did put in a larger jet. I don't have any way to check A/F ratio.

Click to expand...

How about the old way of reading the plug's? Nice medium tan is about right on A/F ratio

Howdy Back Ralf and All:

I did not mean that 215 CFM on a stockish 200 is too much carb. Assuming that it is tuned right, it is just about right for performance. Here are some estimates from the compression calculator on our web site.

On a stockish '74 200 with an 8:1 CR, assuming 80% VE @ 4,500 rpms would require 208 CFM to achieve 106 hp. So the stock Carter YF @ 187 CFM would not achieve that hp #. It would run out of breath somewhere near 4,000 rpms.

On the same stockish 200, but with a well done head- 9:1 CR, back cut intakes, three angle valve job and pocket porting, moving the VE up to 85%, at 4,500 rpms requires a carb capable of flowing 221 cfm. The 221 cfm rating will only be required at high rpms, so a carb rated at 215 should do nicely, most of the time. Changing the cam to a more performance oriented one may change these figures some depending on your choice.

Of course these estimates assume that all engine functions are optimized- ignition timing, plugs, carb tune, etc....

The RBS is capable of more cfm then it's factory rating, with just a little tweeking and polishing too.

So, go for it and let us know your results.

Adios, David