Seondary Pump Tuning Results: I have been chasing a 50-55mph to WOT rich spike (10.0 to 12.2 A/F spike) and I have finaly made some progress. I was also trying to tune my idle to WOT rich spike of 10.0 to 12.0 A/F which was making the car a dog off the line with the DP carb. With my backup DP on the shelf, I started playing with the secondary pump/cams/arm trying to limit the fuel from the secondary side to try and limit the rich spike. After grinding down a black cam, I noticed the A/F spike getting leaner but not nearly enough. Then I added an air gap at the black cam and pump arm screw and it got a little better. So I knew if I could limit the secondary side more then I should see the results. Then I grabbed a pink cam which has a very slow lobe and I rotated the cam CCW as far is it would go to get the least amount of fuel from the secondary side as possible at WOT. I was not sure that it would work because it did not produce much of a pump shot at WOT. So I went out this morning for a test drive and I am so suprised at the result. Limiting the secondary side of the DP gave me instant tire spin from idle to WOT. Of course I wanted to test this over and over and over again to make sure but after several idle to 100% WOT shots, it was immediate tire spin each time. My idle to 100% WOT A/F showed an immediate lean spike to 16.0 but the tires still spun like mad. The 16.0 spike then richens up very quickly to about 14.2 during the tire spin and then drops down into the 13's as the mph comes up. The lean spike does not appear to hurt the performance but I am going to test a larger primary pump cam to see if this helps. The larger primary cam will also help my light throttle A/F which is now into the 15's with the cooler weather. The warmer afternoon temps may show a richer A/F too. Note: this was with the secondary linkage set at 60% delay. Then I tested my 50mph to WOT rich spike and I was again surprised. My rich spike is now at 12.4/12.6 right where I was hoping. After a 50mph to WOT run, the rich spike starts at 12.4/12.6 then then slowly rises to the 12.8 WOT shift point. Then I tested idle to WOT thru both shift points and they both showed 12.8. I am very pleased!! I am very surprised at the idle to WOT response since the secondary cam has been delayed.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)
My idle to 100% WOT A/F showed an immediate lean spike to 16.0 but the tires still spun like mad. The 16.0 spike then richens up very quickly to about 14.2 during the tire spin and then drops down into the 13's as the mph comes up. The lean spike does not appear to hurt the performance but I am going to test a larger primary pump cam to see if this helps. The larger primary cam will also help my light throttle A/F which is now into the 15's with the cooler weather. The warmer afternoon temps may show a richer A/F too.
