Holley/Proform 50cc pump install

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Cudafever

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I have had a carb stumble for a couple of years now, that isn't a problem, if i roll the throttle instead of stabbing it...........
Well every once in a while i forget to roll the throttle(usually while competing)......stab.....stumble.....****.

I got me a 50 cc Squirter Pump and installed it tonight.
Kit came with 2 pump cams, a brown and a yellow. Yellow had a larger.....base circle? Assuming that it was for a Dominator carb, so i used the brown one. It only has One hole. in position #1 on the carb, there was more play then the adjuster could take up. Moving it to position 2 worked but, would start to travel off the cam, causing the pump to start to release at full throttle.

Bent lever so that it would be adjustable in position #1. Problem, was that the cam ramp was to flat and wouldn't squirt at the first motion of the throttle.
Drilled a 2nt hole in the brown cam and reinstalled/adj it. still to slow to activate at first touch of the throttle.

So blue cam when back on. (off of the 30cc pump setup) Touch throttle squirting response is back. way to late to start and test it.

NOW After All of That.
Do the 50cc pumps use the same cams, or is there a completely different pump cam kit, for the 50cc?
 
if i remember the 50 cc just allows for more volume,what discharge nozzle are you useing, factory # 28 ,i like #31 that clears up most bog, hesitation.
 
I run blue cams #1 hole on my 340. 37/39 nozzle high flow screws. If you are above 1k rpm leaving the line use #2 hole up front. I made my own custom length bolts to get the slop out.
 
Any cam that could be used with a 30cc pump.......turns your 50cc pump.....into a 30cc pump.

The potential added volume afforded by the 50cc pump comes from the added stroke the larger cam provides.
 
Snake said:
if i remember the 50 cc just allows for more volume,what discharge nozzle are you useing, factory # 28 ,i like #31 that clears up most bog, hesitation.
Click to expand...
I went all the way up to 35s but the 28 works better, in the front because the squirter last longer. or longer duration.
Here is a video that shows my Problem.

 
Did you also get the 50cc pump ARM?
 
As RRR said, you have to be using the correct arm.

Here is a pic of the 50cc stuff as it comes installed from Holley on the secondary side of a std 850DP.

On this carb, any rotation of the shaft results in movement of the pump arm, and it’s adjusted so that at WOT the pump is almost bottomed out(full stroke).

319588B0-3B37-417F-95C2-B1802F3E3480.jpeg


56D9ACE1-1759-4350-9BAC-A710F84027D5.jpeg
 
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Power valve? I went through the bigger pump , all sorts of nozzles for an off idle hesitation/bog issue.
Turned out the I had to go to a higher rated valve.
I'm using 31 extended nozzles front and rear
 
RustyRatRod said:
Did you also get the 50cc pump ARM?
Click to expand...
yup complete kit. Even came with pivot shaft, screw and C clip.
fishmens67 said:
Power valve? I went through the bigger pump , all sorts of nozzles for an off idle hesitation/bog issue.
Turned out the I had to go to a higher rated valve.
I'm using 31 extended nozzles front and rear
Click to expand...
My 50 cc is on the front.
When out, tested blue cam, no improvement.
Drilled another hole and installed the Brown can that came with the kit.
Squirts at the touch of the throttle...........tested.........marginally better.
Remove my 28 squirter and replaced it with a 35. off idle, i wouldn't say its a bog anymore, but slightly flat.......When stalled at 2000 rpm, what i leave the line at, its sharp/clean. Before that is when it would stumble the most. So major improvement.

Next step.
I noticed that my front fuel bowl is slight below the fuel line in the sight glass so i need to address that. Then when i get back up to the track, adj my 4 corner mixture screws. I haven't played with them for while.
 
Then if you bent the arm, something was wrong. You should never have to do that.
 
Everyone has their own way of doing things......

That being said, I find that I’m adjusting/bending the pump arms more often than not when I’m tuning the accelerator pump circuit.

I’ve kind of adopted the view that when it comes to carb tuning........whatever someone is doing........that’s working out for them......is fine.

Watching Cudafevers video........I think most of his stumble could be resolved by slowing his right foot down a bit.

When I was racing regularly, I learned how to “quickly apply the throttle”, in a nice fluid motion.
As opposed to “stomping” on the gas.
 
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PRH said:
Everyone has their own way of doing things......

That being said, I find that I’m adjusting/bending the pump arms more often than not when I’m tuning the accelerator pump circuit.

I’ve kind of adopted the view that when it comes to carb tuning........whatever someone is doing........that’s working out for them......is fine.

Watching Cudafevers video........I think most of his stumble could be resolved by slowing his right foot down a bit.

When I was racing regularly, I learned how to “quickly apply the throttle”, in a nice fluid motion.
As opposed to “stomping” on the gas.
Click to expand...
yup!
You are the one that taught me that one. But some time i for get and she stumbles.
I'm also doing the 50 cc because i "think" i can get a better 60' time.:lol:
 
PRH said:
Everyone has their own way of doing things......

That being said, I find that I’m adjusting/bending the pump arms more often than not when I’m tuning the accelerator pump circuit.

I’ve kind of adopted the view that when it comes to carb tuning........whatever someone is doing........that’s working out for them......is fine.

Watching Cudafevers video........I think most of his stumble could be resolved by slowing his right foot down a bit.

When I was racing regularly, I learned how to “quickly apply the throttle”, in a nice fluid motion.
As opposed to “stomping” on the gas.
Click to expand...
I agree, I've just never had to do that one.
 
Not a lot of option in a 50 cc pump cams........not that that is a bad thing really.
carburetor 50 cc accelerator pump cams - JEGS High Performance

It says that the red one is for a 30 or 50 cc pump.
I'm going to have to dig through all my Pump cams to see if i already have that Red Cam

The yellow one in my kit won't fit. must be for the 4500 Carburetor.
 
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In your second video, it looks to me like the secondary and primary boosters have a little too much delay in pulling fuel after the blades go wide open. You said the primary bowl float needs to come up higher, and it looked like to me that the secondary float is to low also. Turn the idle up a little higher and adjust your idle screws and pump arms to the new idle setting, so the engine does not try to stall every time it comes back to idle. It's a race car you don't need that perfect idle for the traffic lights, just one that keeps the engine happy. It's the age old story give the engine what it wants not what you think it wants and it looks like it wants a quicker response from the boosters. So raise the floats till you get a more instant response from the boosters, and then go back to tuning your pump shot.
I am not a carburetor expert, just a guy that has run into this kind of problem before and what I did to correct it.
 
Thank you!
That's how i feel and it's funny that you could Not see my float levels but hit it spot on. front fuel was down, and the rear one was down slightly as well.
Adjusted them both, and will be doing another test in a while.
 
Raised float levels on front and rear bowls
Warmed and set idle mixture screws, in gear(gained 200 rpm)
tested......No stumble but now it goes right to 3000 rpm and then climbs to my stall at 4000 rpm.

So now, i either have two much squirter or to much pump......Changed #35 squirter back to #28

Wow i think i have a new car.
video coming right up........................well in the next hour or so.....................
 
Here is a pump cam chart that I found to be very helpful.
If I remember right the brown and yellow cams will only work to there potential with the 50cc pump and arm.Now with that said I believe quick fuel has an arm that is for 50cc pumps but is low profile and doesn't

carb-science-series-accelerator-pump-tuning-for-holley-carburetors-2019-11-04_20-26-50_938332-...jpg
look like the 50cc holley arm.
Good advice from all here.
 
Thank you!
That will be helpful if i need to fine tune the squirter cam some more at the track.

Sad part is my next race is Aug 19 and it's a street tire only race.
Sep is are last race of the season and is a slick race.
 
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