How much carb is too much carb?

[MIKE/ILLINOIS]

Hello all! I'm planning to build a 250 in the next year or so. I've got the Falcon six handbook. I originally was thinking of a 3x1 setup, more for the looks although I do want performance too. After studying the handbook I'm kinda thinking about a 2 carb setup. I've seen Mustang Geezer's website (totally awesome site btw!) and like the dual YF setup. But it sounds like Doug is saying in his caption that it was better on the top end 3500rpm+ and maybe not as good down lower. Maybe too much CFM? I'd also, like some opinions on maybe 2 5200's. Again, could be too much at over 400 CFM. However the venturis are pretty small and the carbs are progressive so it might work O.K. I'll use headers, probably 264 cam, electronic ignition, etc. Sorry for th e lengthy post. Let me hear your input. Thanks, Mike

 

[xctasy]

Talk at once to stang 200. Chris has looked at doing this.

In Europe, a few twin carb BMW 3.0's and Mercedes Benz 250/280 models used very similar Solex 2-bbl carbs to do the same job. In the days of cheap fuel and the treat of Arab fuel rations, the Germans decided to leve the combinations as they were for many years. Injected engines were just around the corner. As they were, they were very thirsty, but those little sixes were very heavy and had rev ranges up to the 6000 rpm plus area. Solex carbs were not very realible in the way a US carb has to be. A nice 200 with even a stock camshaft would do well with the US spec 5200 carbs.

The trick is to get the linkage working well, and tailor the idle and secondary jets well. The little 97 cube European Pinto SOHC engines were never released in America, but they ran 75 hp form just one carb with the same jetting as the Pinto 2000. (121 cube)

I'd start with the 5200 Holley Weber, and then apply a gas anaylser or maybee an onboard oxy sensor gage to get the air fuel mix right. The idle correction may need to be changed, and the two chokes would have to be syncronised in some way for cold starts.

 

[Anonymous]

I've seen Mustang Geezer's website (totally awesome site btw!)

Thanks!

It wasnt too much cfm's IMO.....the venturies are so big on a carter YF that I think it just couldnt keep the velocity up until it reached the higher rpms...if that makes any sense

They are only rated at 190 or so cfm's a piece but when you compare them to say a Holley 2 Bbl they have a lot larger, venturies/throttle plates, etc...

I thought that weber made some small 1 bbl carbs in the 150 cfm range. Somthing like that would be excellent IMO!!

I just wanted the adjustability that you can get from a holley carb....thats why I changed...

Later,

Doug

 

[MIKE/ILLINOIS]

Thanks xtaxi for your reply. I will have to get in touch with Chris as I think he is located in St. Louis which is just across the river from me. And Doug, yes that does make sense about the larger venturis being the problem rather than to much CFM. That's why I was thinking about 2 of the 5200's---relatively small venturis to keep velocity up but will it be too much flow for the 250 to handle? Any more opinions or comments welcomed!! Thanks, Mike.