Originally Posted by
brute4c
In response to the original question....
The stock 1920 1 barrel has worse fuel mileage and less power than the approx 350 cfm Holley 2415 2 barrel I now have from a civvy 230...there was also a 2300 Holley 2 barrel used on civvy applications, also approx 350 cfm.
The 2 barrel has noticible power and mileage increases as one doesnt have to hold the throttle open as far or as long to get the same speed.
With a stock 230, roughly 9 MPG was the limit. With a civvy ignition, Selectros and the 2 barrel, these changes done in stages not all at once, netted 12.25 MPG highway and single tanks in excess of 280 miles without a stop.
NOTE: The change to the 2 barrel DOES lower the torque right off the line. One can still start the truck n gear with the starter button and idle along at 500 rpm in 1st gear but when taking off from a dead stop 2nd gear, high range, one will notice the engine lugging a little where it didnt with the 1 barrel.
So, for low end torque, as small a venturi or venturis as possible...if there is even a 300 cfm or smaller 2 barrel out there that would fit...
If you are willing to sacrifice a little on the low end you can get better mileage and power across the rest of the rpm range with approx a 350 cfm carb.
Find a way for the intake side of the head to breathe better and you can go higher...as it is stock, the ports from the intake into the head, when figured in area, are only a slight fractional size different than the throttle plates on the 350 cfm 2 barrel...I believe the difference was less than 1% in total area across both...real close.