1.5" carb on a 1.75" carb head

[Anonymous]

ive been trying to find an adapter to make my 1.5" bore carb fit on a 1.75" bore head. The company has none for my carb available. anyone know where i could find one? Thank you very much for your help!

-Tony

 

[MustangSix]

Just mark, drill, and tap two new holes in the head and mount the old 1.5" base. I've done this a couple of times with no problem.

 

[CZLN6]

Howdy Back Tony:

If you don't like Jack's solution, you could also simply slot the mounting holes in the carb base wide enough to fit the mounting stud.

Adios, David

 

[Anonymous]

increase slots to bolt on manifold, but what will be lost ? fuel economy because less air is available due to smaller carb opening. was told the carb nbr 4784s was for a 70 ford or mercury 6 inline 250. did ford make a 1.5 throttle opening head in 1970 ?

 

[CZLN6]

Howdy Whipper:

Performance will be lost- but only a little. FoMoCo moved up to the larger throttle bore carbs and to a 1.75" carb hole in the log during the '69 year on some castings. By '70 all heads were the larger hole size. Carter YF carbs of that era were rated at 197 cfm on 200s and 150 cfm on 170s. If you use an early smaller throttle bore 200 rated carb on a larger carb hole head, the key will be the size of the inner diameter of the venturi. Both are rated at 187 cfm.

The 1970 250 engines would have had the Carter RBS carb rated at 215 cfm and different in appearance from the YF models.

Officially, Ford did not use the smaller diameter throttle bore carbs in 1970, but, when it comes to Ford, Never say never.

Adios, David

 

[Anonymous]

Hey David,
MAYBE THIS COULD SHED SOME LIGHT.. I DO HAVE A CARTER RBS 1.75 NOW INSTALLED ON MY 1980 HEAD 250 IT STATES ON THE SIDE OF CARB " CARTER MADE FOR MOTORCRAFT" BUT THE 1.5 HAS CARTER ONLY ON THE SIDE. DID NOT CARTER ALSO MAKE FOR AMC LIKE THE RAMBLER BACK IN THE 60'S . THE CARB. SHOP SHOWS THIS NBR CARTER 4784S FITS THE 1970 FORD. iT IS THE FUEL PUMP AT INITIAL STARTUP THAT DOES NOT PUT ENOUGH FUEL IN THE CHAMBER WITHOUT ABOUT 5 TO 10 PUMP WITH THE 1.75 INSTALLED NOW.