Carter RBS swap info?



I was reading the other posts about the carb cfm and saw that the carter RBS had the most cfm for a 1 barrel carb and was used on the 250's. i just wanted some info on swapping one into my car. would you need to make the intake hole to 1.75"??? you know just what would be involved and if this isnt such a good idea for a 1 barrel carb upgrade then what would be a good one? i have a 1100 right now. need more 8). thanks alot for the help guys.
Howdy PonyRider66:

You didn't say what distriburtor your using. If it's still the Load-A-Matic, vacuum advance only, that will make a difference in what I reccommend. Is your Mustang a Calif. car? Are you willing to adapt/modify linkage?

The Autolite 1101 is also a 215 cfm carb and closest to a bolt on. It does have a 1.75 carb bore. It was only used in 1969 on 250 engines. For best results you should also upgrade to a '68- 69 distributor, with both vacuum and centrifugal advance. Your Petronix should swap over.

The Carter RBS is slightly lower profile and was used on 250 engines from 1970 to about '74. It also has a 1.75 carb bore, and a different fuel line and linkage configuration. The later distributor mentions above would be a good idea here too.

Plumb the vacuum advance line from the new distributor to the ported vacuum source on either carb. You'll love the difference.

Adios, David
PonyRider, I have an RBS in my hand right now. I just measured the carb bore. Contrary to popular opinion it is one and nine sixteenth inches in diameter at the throttle plate outlet ( the part that bolts on to the manifold). hope this helps-----------Larry
PonyRider, I can give you some more information. I also have an 1101. the RBs and the 1101 are exactly the same height and have the same general profile. The fuel inlet is the same and the throttle linkage is the same. Both will be the same as your 1100. The only difference I can see that might cause you some problems is the choke. the RBS has the typical carter heat tube vacuum piston automatic choke while the 1101 I have has a manual choke. I prefer a manual choke and when I ran the RBS I converted it to a manual choke but all youd have to do is run a heat tube from the choke housing to your exhaust manifold if you dont already have one. The only major difference in the two carbs is how they make their cfms. the restrictor in the throat is the same size on both carbs, the bottom hole of the RBS is one and nine sixteenths while the top hole is two and three sixteenths. The bottom hole of the 1101 is one and eleven sixteenths while the top hole is Two inches. They flow pretty much the same cfms, give or take a few but seem to have a reverse pattern of doing it. Of course with the different top hole dimensions you would probably need a different air cleaner. If you have a vacuum advance on your distributor both carbs have a veturi vacuum outlet port for a vacuum hose. Good luck on your choice----Larry
Everyone says the bigger carbs. have a 1.75" bore just for convenience, basically, rather than specifying 9/16 or 11/16. In fact, if you measure the 1100, it's bore is not perfectly 1.5". It's a little smaller.
thanks alot for the help guys. ok so in order to do a either autolight 1101 or a RBS swap i would need a new dizzy, make the bore in the intake mainfold to 1.75" and then the rest is just easy throttle and vacume adjusting right?
ponyrider, there is alot of difference between 1 3/4 and 1 9/16, if your manifold is 1 1/2 and you used the RBS you might not even have to open it up it would just be 1/32 of an inch smaller all around . If you did open it up you would have a lot less grinding or machining to do about 3/16 of an inch lessthan if you used the 1101. and you can use your old disrtibutor until you get an upgrade . just some more to think about ----larry