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Old 09-21-2012, 03:48 PM
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My New Way to Measure the Holley Pump Shot

If you follow the Corvette Forum you may know that I've been fighting a rich bog associated with the pump shot on my Holley 600 dp.

I determined that there had to be a way to measure the shot while observing its characteristics.

I came up with an idea so that I can now very accurately measure the volume of the pump shot while observing the fill pattern. You guys who are losing your hair will instantly recognize this for what it is.

This will "self thread" into the hole once the squirter is removed. A nylon washer seals the bottom. When you pump a shot and the volume comes to a level and does not leak down, the seal is tight. In fact, you must unscrew it a bit to let it leak down between shots. I'm using water here.

I don't know if anybody makes anything like this for the marketplace. Sure would be easy to produce and a great tuning tool. It's just a plastic graduated cylinder and could be made with a proper fitting and seal and bleed down valve. My idea, just send me the first one!



Well it would appear that every centimeter of tube length represents 1/4 ml (i.e., 1/4 cc). Nice! Makes it easy.


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Old 09-21-2012, 04:22 PM
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If it had an o-ring and a check ball with an open top,you could just pour it out after each test.and do it on a car with out filling the manifold with fuel
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Old 09-21-2012, 04:29 PM
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Might be a good way to measure while on the bench but what about real world testing with the motor running at different rpm's. The amount of it's shot and characteristics would change I think.
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Old 09-21-2012, 04:46 PM
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of course the engine would have to be off,lol. I see that tool as similar to what pilots use to test fuel as a preflight inspection. Look at the colour/clarity of the fuel in the bottom of the bowl.Checking the volume is a bonus. Cam profile and squirter size is the behaviour,also combined with a different CC pump.also to confirm the the 50 cc pump the guy said he installed is there,,,
great idea,not solving all the worlds problems,just helping a little.
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Old 09-21-2012, 04:48 PM
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I dont quite get what your trying to measure are you measuring if your getting the full 50 or 30 cc from your pump? Because the duration (time it takes to pump the 30 cc's through the pump discharge nozzles) is controlled by the size of the holes at the discharge point of the nozle and the pressure of the spring on the fuel pump actuating arm and the pump cam ! And how well the ball seals at the bottom of the bowl!

Please elaborate Im interested!

Jester
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Old 09-21-2012, 06:46 PM
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BTW, the advertised volume of the various accelerator pump cams is per 10 strokes of the accelerator pump. Just so there's no confusion.

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Old 09-21-2012, 06:52 PM
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I am measuring the actual volume of fuel that is being delivered by the squirter nozzles. Just because you have a 3 or 5cc pump doesn't mean that you use all of that capacity. You only use as much capacity as the pump cam "plunges" out of its bore.

I have a rich bog that comes on with the pump shot so I am looking to reduce the volume of fuel being squirted. The squirters control how long it takes to discharge this volume with a smaller squirter taking more time and I've already gone to the smallest squirters so I need to reduce the volume a bit.

But what is the volume???

For example the Holley Manual lists that the "pink" cam squirts 1.8ccs in Position 1 and 2.25cc in Position 2 for a squirt if you extraolate the 5cc pump to a 3cc pump. So, if you want a leaner squirt, you would use Position 1.

I measured 2.20cc in Position 1 and 1.83cc in Position 2 for a squirt with a 3cc pump. This is just the opposite of the published values and I confirmed it with several other pink cams. Very strange!

Holly lists the blue cam at 1.08 cc per squirt in Position 1 and 1.17 cc in Position 2.

I measured 1.45 cc in Position 1 and 1.69 cc in Position 2.

It should be of note here that every chart you see for these pumps are based on the 5cc pump and maybe these values can't be directly extrapolated to the 3cc pump. That being the case, I don't think there is any 3cc pump data to be had.

Last edited by toddalin; 09-21-2012 at 07:00 PM.
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Old 09-21-2012, 07:31 PM
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Thats what I thought Just wasnt Quite sure.

Jester
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Old 09-21-2012, 07:57 PM
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Are you just checking or are you modifying your cams by filing the ramps and are you testing on a dino with a load? For your results? Or at a track?


Ive filed and swaped cams & switched squirters at the track but that was by the seat of my pants LOL I even had a dino in my shop but never thought to do dino tests or record results! your very innovative Id be interested in your results.

Jester
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Old 09-21-2012, 10:47 PM
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Quote:
Originally Posted by painted jester View Post
Are you just checking or are you modifying your cams by filing the ramps and are you testing on a dino with a load? For your results? Or at a track?


Ive filed and swaped cams & switched squirters at the track but that was by the seat of my pants LOL I even had a dino in my shop but never thought to do dino tests or record results! your very innovative Id be interested in your results.

Jester
Dyno testing, but only when the occasion arrises every couple years. I watch the A/F and its effects on the torque. The pump shot was creating an over-rich mixture. If have re-profiled some pink cams for less delivery and will give it a shot (pun intended) when the weather cools.

Also, my testing shows that the numbers for the pink cam are reversed from published values. (I know it's crazy.) I may be able just to use the other position now that I know that it delivers less rather than more fuel on a shot.
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Old 09-22-2012, 07:42 PM
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Quote:
Originally Posted by toddalin View Post
I am measuring the actual volume of fuel that is being delivered by the squirter nozzles. Just because you have a 3 or 5cc pump doesn't mean that you use all of that capacity. You only use as much capacity as the pump cam "plunges" out of its bore.

I have a rich bog that comes on with the pump shot so I am looking to reduce the volume of fuel being squirted. The squirters control how long it takes to discharge this volume with a smaller squirter taking more time and I've already gone to the smallest squirters so I need to reduce the volume a bit.

But what is the volume???

For example the Holley Manual lists that the "pink" cam squirts 1.8ccs in Position 1 and 2.25cc in Position 2 for a squirt if you extraolate the 5cc pump to a 3cc pump. So, if you want a leaner squirt, you would use Position 1.

I measured 2.20cc in Position 1 and 1.83cc in Position 2 for a squirt with a 3cc pump. This is just the opposite of the published values and I confirmed it with several other pink cams. Very strange!

Holly lists the blue cam at 1.08 cc per squirt in Position 1 and 1.17 cc in Position 2.

I measured 1.45 cc in Position 1 and 1.69 cc in Position 2.

It should be of note here that every chart you see for these pumps are based on the 5cc pump and maybe these values can't be directly extrapolated to the 3cc pump. That being the case, I don't think there is any 3cc pump data to be had.
That would be a 30cc/50cc pump capacity. That is the max deliverable per 10 strokes, nominally.

The pump charts aren't all based on using a 50 cc pump- many of the pump cams made for the 30cc pump don't work right using the 50 cc set-up, and vice versa.

While the different positions (positions 2 0r in some cases position 3) will deliver differing volumes, the reason for position 2 is for cases that require a large primary throttle opening. The #2 position rotates the cam around to still allow a full pump shot in those cases. If #1 hole were to be used, a portion of the pump shot wouldn't be available.

Last edited by cobalt327; 09-22-2012 at 07:47 PM.
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Old 09-22-2012, 07:51 PM
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Originally Posted by cobalt327 View Post
That would be a 30cc/50cc pump capacity. That is the max deliverable per 10 strokes, nominally.

Excuse me. If it takes 10 strokes to make 30cc, that's a 3cc pump. I just call them what they are.
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Old 09-22-2012, 07:59 PM
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Have it your way. No one says "3cc/5cc pump" in my experience, but what do I know? Maybe you can start a trend.

Good luck.
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Old 09-22-2012, 08:04 PM
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Quote:
Originally Posted by toddalin View Post
Excuse me. If it takes 10 strokes to make 30cc, that's a 3cc pump. I just call them what they are.


Cobalt probably does too! lol go into a parts store and ask for a 3 cc pump LOL I think he was just pointing out what most people other then carb builders didnt know on how it was actually measured! I said in my one post are you measuring to see if your getting the full 30 cc's . and he posted the procedure.

Jester
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