Pump Cam curve Question

[CDN]

Tuning for street driving manual trans want to delay pump shot a bit on light throttle
Primary side : 80513 4150 carb which pump cam ( have pink & blue ) has the slowest curve ?

[Nick_nl]

You could move the screw to the "2" position. This delays the pump shot to further in to the rotation.

[CDN]

Tks I should have said I use #2 position have 1100 idle
I know the blue has alot less volume than pink but do they both start at same throttle opening or does one start later ?

[Nick_nl]

Well you could have a look at the pump cam chart. It shows cam lift vs rotation angle.
This chart would indicate that the pink one has the slowest curve.
You could just try it, it's only one screw

[74 roadrunner]

Looking at the pump cam chart from Holley the blue cam has more pump cam lift and throttle rotation than the pink cam.

[CDN]

Yes I have the chart just not sure if Im just not sure if im understanding it correctly
The pink cam has almost double the capacity as blue
but over more throttle opening so does that mean it starts slower ?

[Nick_nl]

Would this be driving very gentle?
I have been working on the pump cam too and saw that when really slowly opening the throttle there is no pump shot. The white cam for example went on longer, the orange one was done faster. Both were with a 31 nozzle. I didn't measure the volume.
Just looking at the cams the pink one is very gentle. The Blue one is like hitting a wall.

What's the issue your trying to fix?

[CDN]

Yes on the throttle very gentle when normal street driving het a rich spike 12.2 when pump comes in
Expect that of course however if I could delay it a bit and not so ruch would help overall afr in cruise
No driveability issue working on overall crruise afr with IFR &IAB changes and making progress just thinking about accelerator pump cam / squirter tuning when I get afr as good as I can
At this point just a thought
One change at a time

[Nick_nl]

You could also use a smaller nozzle, that will lengthen the pump shot duration. The same amount over a longer time period. Though this might give a lean bog during hard acceleration.
I wouldn't worry to much about this item, fuel mileage at steady cruise is more important.

[57 210]

The method I use for to determine pump cam suitability is to hang them on a round rod or screwdriver shank the size of a throttle shaft lined up with the flat sides all on the left then pin all the # 1 holes and squeeze them together. You can then look down the apexes and determine which one is best for your application. This method is eye opening and gives you the best understanding of different cam operation. Use this along with pump cam chart volumes to make your selection. Everyone should try it.