21-01-2020, 10:07 PM
(This post was last modified: 21-01-2020, 10:16 PM by Bob Culver.)
This was all thrashed out some years ago but I do not have the reference. A complication is the lack of written designation on the parts and the interchangeability of the tops; ie dashpot or not. Only the output dia seems to differ between the 1 inch and 1 1/8 inch and on stock non sport cars the piston seems to seldom or ever lift fully so any performance difference unlikley, although a small outlet gives a more progressive throttle. Later semi downdraught look wrong on a 1930s car. Note that when comppring needle shapes only the diameters in range of lift are invoved in normal running. I only have experience of the 1 1/8 dashpot on a mildly altered RP. Seemed surprisingly beneficial ; much as the 1937 head. And car could be driven very smoothly in downtown traffic crawls as applied before the stop go sprints associated a myriad traffic lights.