[rod]

to set the slapper bars right, first the pinion angle must be correct. then the car must be race weight and race ready. either weight the driver seat [some weight must be on the floor board, to simulate leg weight] or find someone exactly the same size and weight to set in the driver seat. then set the bars. both should be the same-distance or compressed. with the weight out of the driver seat, the pass side should remain the same and the driver side should have a gap. more gap, on both bars, will equal a harder hit, less air gap will equal a softer hit. adjust the bars depending on what the car requires to get the 60 you want. leaf spring cars should rise at the rear [not squat] if the car does not rise, you must change the angle of the bar [read higher in the front]. most Camaro/Firebird cars have the front spring eye the same height or lower than the center of the axle tube. the only way to make the car rise in the rear, especially if the front of the car is lower than the rear, is the make the front of the bar contact the spring some distance behind the spring eye. it will be hard on the spring over time. however, if the car does not rise, you are fooling yourself.
some thought should be given to putting both shocks on the same side of the axle [if rule legal]. shocks should be as straight up/down as possible.
you should also fab up some sort of safety loop, at the front of the bar, in case the bar should break and dig into the strip.
over the years I have seen a lot of really fast slapper bar cars. I once watched a big block Camaro almost pull the rear tires off the ground on gear change. I made a few suggestions and the car picked up 4 tenths. with only a slapper bars angle change, totally free, that is a deal.
when it is race time, you need lots of videos. I dont care how much you think you know from the driver seat, nothing beats a photo.
Rod in AZ