EXACTLY!! When you watch the linkage on the carb go from a steady cruising position to WOT, the secondary linkage moves so fast that the air gap is taken up in a flash. With the correct secondary squirter, I can not feel any hesitation at all with a large air gap.
I am currently testing the secondaries with the pink cam which has a very slow ramp speed (& medium sized volume) and I am using a .048 squirter on the secondary side to help speed that back up. If I was to use a quicker ramp speed cam (maybe a black), then the squirter will prabably be smaller. What I am trying to achieve is to lessen the amount of pump shot given by the secondary cam to lessen my idle-WOT A/F and my cruise-WOT A/F rich spike that I currently have without screwing up my other A/F readings. Since my cruise and my WOT A/F's are very close, I know by the A/F gauge that the secondary cam is giving too much extra fuel when I go to WOT.
Since I know that the pink secondary pump cam is too much volume, I could use a smaller pump cam or just shorten the adjusting bolt to create this air gap on the pink cam. The overall amount of the pump cam is reduced with the air gap (shorten the bolt) and since I had a slight hesitation at 50-WOT with a .037" squirter, I changed the .037" to a .040" to get rid of the hesitation. Since the pump cam is just a "band-aid", that is all that I am using it for. I do not need the entire pink cam's volume, so I am going to make the air gap larger by one full turn and retest. Then if that is still to much volume, then I will make the air gap larger by one more turn and retest again. Then if I run out of bolt adjustment, I will drop down to the smallest pump cam and retest. I did this several times last year and I have charted some of the changes. Since I made some ignition changes over the Winter, I am now just re-tweaking the rear pump cam to finish the tuning process.
I agree that the .042" primary squirter "seems" huge but I am using one of the smaller pump cams (red) and the Red/.042" combo keeps my acceleration A/F numbers in the range that I want. The squirter just speeds up or slows down the volume created by the pump cam. Since I do not want to increase the overall volume of the primary pump cam, I just want to adjust the speed of it by using a larger squirter until my A/F numbers are where I want them for accel. If I was using the stock #68 primary jets, then I would guess that I would be able to use a much smaller primary squirter. But since I have dropped my main jets from the stock #68 to now #60's, and I am able to use a smaller red pump cam, then I need the larger squirters to help tune the speed. I am running 30 of timing at idle. This might be some of the reason that a .042" primary squirter gives me a better A/F than a .037" primary squirter on light - medium accel.
I have found that since I have done so much tuning on the other circuits, that now I am down to just juggling the secondary cam and squirter to keep my A/F in check. The .042" squirter is not what "everyone else" is running, but neither are #60 primary jets. This is exactly why these O/2 sensors are such a great tuning tool.
I now totally understand why some people say "do not use a DP carb on an auto car on the street". They can be a bear to get the mechanical secondaries tuned. But I can now see exactly what my A/F is doing from idle-WOT and from cruise-WOT and I can correct the amount of fuel that the secondaries are adding which is causing my rich A/F spikes at WOT situations. I have found that in my case, limiting the secondary pump cam volume is the key. Is "everyone" tuning their DP like this? NOPE!! Can "everyone" running a DP see what I am seeing? NOPE!!
Thanks for the response and get that new float installed!
