Carbs-Refresh my memory
- Thread starter bmcgc1960
- Start date
The Falcon Six cylinder handbook covers the 144 to 250 engine carburation in some detail.There are SCV and non SCV carbs, very important since stock Ford I6's are very sensitive to distributor set up. Most pre 1968's were SCV, but the California vaersions were non SCV from 1967, I think.
The stock 1-barrel (1-bbl) cfm rates are measured at 3 " Hg, or 40 " H20 pressure drop, and the flow rate of any 1-bbl carb is generally 1.41 times that of a 4-bbl carbs flow rate. A 390 or 600 cfm 4-bbl carb would rate at 550 cfm and 846 cfm if the pressure drop was as per the 1 and 2-bbl carb rating system.
4-bbl carbs are measured at a 1.5" Hg (20" h20) pressure drop, half that of a 1-bbl and 2-bbl carbs. When Ford made Holley Weber 2-bbls standard in the Pinto, it was rated as a 280 cfm at 3.0" Hg (40" H20). Comparing a 2-bbl to a 1-bbl is generally the same basic system, but some 2-bbl Webers are rated at 1.83" Hg, just to totally mess you up. So beware when comparing them to 1-bbl carbs.
The ratings vary from s little as 125 cfm for the first 1904 Holley 1-bbl on the 144 to well over 215 cfm for the 250 cubic inch engines Carter 1-bbl. Throughout the years, there were some back flips, and similar replacement carbs which were inferior to the earlier standard items, but there were important reasons for this. Depending on the head used, the carb hole size varied from 1.3 to 1.6875" to 1.75", and the two stud pattern from one type to another. The 1966 to 1987 carb 240/300 big sixes had non SCV 1-bbls carbs which flowed better than the small six carbs, and these do swap with some modification to the stock stud pattern on pre 1969 small six engines, and are easy swaps on to the later small six heads. Some 1940 Autolite replacements made by Holley were small bore, some large, and so there is a lot of specific info needed to make a replacement Ford carb work better than the stock non SCV Autolite 1100 carbs.
The best flowing carbs are the replacement 1908 carbs from Classic Inlines, they are reproductions with bigger internal dimensions and better flow rates than the standard items, but are non SCV.
The stock 1-barrel (1-bbl) cfm rates are measured at 3 " Hg, or 40 " H20 pressure drop, and the flow rate of any 1-bbl carb is generally 1.41 times that of a 4-bbl carbs flow rate. A 390 or 600 cfm 4-bbl carb would rate at 550 cfm and 846 cfm if the pressure drop was as per the 1 and 2-bbl carb rating system.
4-bbl carbs are measured at a 1.5" Hg (20" h20) pressure drop, half that of a 1-bbl and 2-bbl carbs. When Ford made Holley Weber 2-bbls standard in the Pinto, it was rated as a 280 cfm at 3.0" Hg (40" H20). Comparing a 2-bbl to a 1-bbl is generally the same basic system, but some 2-bbl Webers are rated at 1.83" Hg, just to totally mess you up. So beware when comparing them to 1-bbl carbs.
The ratings vary from s little as 125 cfm for the first 1904 Holley 1-bbl on the 144 to well over 215 cfm for the 250 cubic inch engines Carter 1-bbl. Throughout the years, there were some back flips, and similar replacement carbs which were inferior to the earlier standard items, but there were important reasons for this. Depending on the head used, the carb hole size varied from 1.3 to 1.6875" to 1.75", and the two stud pattern from one type to another. The 1966 to 1987 carb 240/300 big sixes had non SCV 1-bbls carbs which flowed better than the small six carbs, and these do swap with some modification to the stock stud pattern on pre 1969 small six engines, and are easy swaps on to the later small six heads. Some 1940 Autolite replacements made by Holley were small bore, some large, and so there is a lot of specific info needed to make a replacement Ford carb work better than the stock non SCV Autolite 1100 carbs.
The best flowing carbs are the replacement 1908 carbs from Classic Inlines, they are reproductions with bigger internal dimensions and better flow rates than the standard items, but are non SCV.
stu in wichita
Well-known member
bmcgc1960":1qj4uhy9 said:
The LOM is extremely simple inside. Pop the cap. You'll see two springs on the point plate, but no mechanincal advance weights and springs.
-Stu
