CHEVROLET Carter YF carburetors.
There have been a number of questions on this and other forums concerning replacing the older Carter type W-1 carburetors and Rochester type B carburetors with Carter type YF. Some have had great success; others less so. This post is an attempt to clarify.
The enthusiast will encounter two major issues with using YF carburetors. The first is the selection of the carburetor; the second is selection of the rebuilding kit to rebuild the carburetor.
Discussing the carburetor selection first: Carter made hundreds of type YF carburetors beginning in 1950 on up through 1986. These were used on applications from Jeep 4 cylinders with 134 CID to Foorrdd 6 cylinders of 300 CID. It is IMPORTANT is use one of the YF carburetors designed for Chevrolet. These carburetors come in 4 groups by size and choke type. The sizes are S.A.E. size 2 which is an inch and one-quarter carburetor with center to center stud spacing of two and eleven-sixteenths inches; and S.A.E. size three which is an inch and one-half carburetor with center to center stud spacing of two and fifteen-sixteenths inches. The two choke types are manual and automatic (when installing a carburetor with automatic choke on an engine which originally had a manual choke, it is necessary to fabricate a “heat stove” to affix to the exhaust manifold).
A listing of Carter YF for Chevrolet
756S size 2 auto choke (1937 and newer engines)
787S size 2 manual choke (1937 and newer engines)
788S size 3 manual choke (1950 and newer engines)
789S size 3 auto choke (1950 and newer engines)
964S size 2 manual choke (1937 and newer engines)
965S size 2 auto choke (1937 and newer engines)
966S size 3 manual choke (1950 and newer engines)
967S size 3 auto choke (1950 and newer engines)
2008S size 2 manual choke (1937 and newer FLEET economy engines ONLY)
2046S size 2 manual choke (1932 – 1936 engines ONLY)
2100S size 3 manual choke (1950 and newer engines)
2101S size 3 manual choke (1950 and newer engines)
The issue with the aftermarket rebuilding kits is quite simple. The carburetors made for Chevrolet were made in the 1950’s and early 1960’s. Most of the YF production was for Foorrdd engines, especially the 300 CID 6 cylinder which require more fuel. MOST (not all) of the current aftermarket repair kits contain a fuel valve designed for the Foorrdd engine which has an orifice of 0.101 inches. The fuel valve as used in ALL of the YF carbs for Chevrolet had an orifice size of 0.081 inches. If you do the math, the valve for the Foorrdd has an orifice size which is seventy percent larger! Using this valve in the Chevrolet carburetor will cause at best an over rich condition at idle, and at worst flooding and fuel leakage.
Jon.
