50cc accel pumps?
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50cc accel pumps?
Someone mentioned 50cc accel pumps as a performance upgrade. I don't know what the capacity of the stock pumps on my 850 cfm Holley Brawler are. I've got a Weiand 142 blower on a ZZ4 crate motor, it isn't slow getting going now - would I likely gain anything?
Thanks.
Thanks.
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a little background...most stock are 30cc which is 3 cc and the upgrade is the 50cc which is 5cc. They are measured with 10 strokes, thats how you get that number.. Anyway the performance upgrade would be in a few waysbut only to eliminate bogs
without a nozzle change you will get a longer duration to your pump shot going from 3cc to 5cc. if you swap to a lot larger nozzle you would need the 5cc to maintain the duration with the larger volume. Then you can start messing with the cams to change ramp speeds for what your squirt would look like.
If you arent experiencing a bog you will not see a difference. The pump is to make up for the increase in air flow when you stab the throttle
without a nozzle change you will get a longer duration to your pump shot going from 3cc to 5cc. if you swap to a lot larger nozzle you would need the 5cc to maintain the duration with the larger volume. Then you can start messing with the cams to change ramp speeds for what your squirt would look like.
If you arent experiencing a bog you will not see a difference. The pump is to make up for the increase in air flow when you stab the throttle
Last edited by Rescue Rogers; May 10, 2022 at 08:34 PM.
Thread Starter
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a little background...most stock are 30cc which is 3 cc and the upgrade is the 50cc which is 5cc. They are measured with 10 strokes, thats how you get that number.. Anyway the performance upgrade would be in a few ways to eliminate bogs
without a nozzle change you will get a longer duration to your pump shot going from 3cc to 5cc. if you swap to a lot larger nozzle you would need the 5cc to maintain the duration with the larger volume. Then you can start messing with the cams to change ramp speeds for what your squirt would look like.
If you arent experiencing a bog you will not see a difference. The pump is to make up for the increase in air flow when you stab the throttle
without a nozzle change you will get a longer duration to your pump shot going from 3cc to 5cc. if you swap to a lot larger nozzle you would need the 5cc to maintain the duration with the larger volume. Then you can start messing with the cams to change ramp speeds for what your squirt would look like.
If you arent experiencing a bog you will not see a difference. The pump is to make up for the increase in air flow when you stab the throttle
Team Owner
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People on the forum that went the 142 route found it's limitations on boost even with bigger carbs and pulleys. The next step was using a NO2 spray plate under the carb. 
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I don't remember any engines that actually needed the 50cc accelerator pump diaphragms.
Even a Custom Built A.E.D. Holley used the standard 30cc pump diaphragms on a 850 Double Pumper for a thirsty high performance Big Block. This carburetor was tweaked to flow over 1100 cfm for my L88 replica.
Unless your engine really needs the extra fuel I would continue with the 30cc pump diaphragms. Squirting almost double the original 30cc's would certainly use a lot more fuel down the road.
Where are the 50cc pumps used? What kinds of applications actually need the extra fuel? Now I am curious....
Even a Custom Built A.E.D. Holley used the standard 30cc pump diaphragms on a 850 Double Pumper for a thirsty high performance Big Block. This carburetor was tweaked to flow over 1100 cfm for my L88 replica.
Unless your engine really needs the extra fuel I would continue with the 30cc pump diaphragms. Squirting almost double the original 30cc's would certainly use a lot more fuel down the road.
Where are the 50cc pumps used? What kinds of applications actually need the extra fuel? Now I am curious....
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The couple of brief stoplight "conferences" *cough* I've had weren't even close, last one was some guy (I assume - it was at night and their windows had dark tint) in a rumbly, dressed up C4. I never went any faster than about 50 and there was a lot of pavement between my back bumper and his front bumper - I didn't even get on it until I saw he was.
Last edited by brassplyer; May 11, 2022 at 02:15 PM.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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2019 C3 of Year Winner (performance mods)
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I don't remember any engines that actually needed the 50cc accelerator pump diaphragms.
Even a Custom Built A.E.D. Holley used the standard 30cc pump diaphragms on a 850 Double Pumper for a thirsty high performance Big Block. This carburetor was tweaked to flow over 1100 cfm for my L88 replica.
Unless your engine really needs the extra fuel I would continue with the 30cc pump diaphragms. Squirting almost double the original 30cc's would certainly use a lot more fuel down the road.
Where are the 50cc pumps used? What kinds of applications actually need the extra fuel? Now I am curious....
Even a Custom Built A.E.D. Holley used the standard 30cc pump diaphragms on a 850 Double Pumper for a thirsty high performance Big Block. This carburetor was tweaked to flow over 1100 cfm for my L88 replica.
Unless your engine really needs the extra fuel I would continue with the 30cc pump diaphragms. Squirting almost double the original 30cc's would certainly use a lot more fuel down the road.
Where are the 50cc pumps used? What kinds of applications actually need the extra fuel? Now I am curious....
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It works great for my tri power setup. With no outboard accelerator pumps I use the extra 2 ccs as I floor the accelerator, they dont run dry while the carbs tri to catch up. I have softer springs in the outboard vacuum pods so they come in faster, with the same squirters,
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Thread Starter
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It works great for my tri power setup. With no outboard accelerator pumps I use the extra 2 ccs as I floor the accelerator, they dont run dry while the carbs tri to catch up. I have softer springs in the outboard vacuum pods so they come in faster, with the same squirters,
Is my vette stock?? HAHA
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From: Im not allowed to tell you
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Heel & Toe
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For reference:
I got an AED 850 Annular Booster Holley.
It got a 30cc stage 1 and 50cc stage 2 pump.
Also it got the blue actuator cam.
It works flawlessly on my 670 hp engine.
Engine builder advised getting a 850 for that BBC so i did..
I got an AED 850 Annular Booster Holley.
It got a 30cc stage 1 and 50cc stage 2 pump.
Also it got the blue actuator cam.
It works flawlessly on my 670 hp engine.
Engine builder advised getting a 850 for that BBC so i did..
Is my vette stock?? HAHA
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From: Im not allowed to tell you
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Unless you are experiencing a flat spot or bog when you accelerate specifically due to a lean spot when you stab the throttle, you wont gain anything. I would make sure your carbs are boost referenced to the manifold below the blower before playing with the accelerator pumps to ensure they are operating properly. This will ensure the power valve opens dumping about 10 jet sizes more fuel into the engine under heavy load with a steady throttle from each carb
Thread Starter
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Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,209
Likes: 9,347
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
if you increase the volume of the pump but dont increase the jet size the squirt lasts longer. As you move through the accelerate range the valve moves so much, but does not refill until you back off the accelerator to reload it. WIth a larger volume you may still have more shot in the chamber so you gain that much more extra fuel for an additional jab if you decide to go further in the throttle. Its not just about the jet size. If you increase the size of the jet, you need to increase the volume to compensate for the pressure drop. I've heard around a 38 jet or larger as well. I will have to look to see what my last squirter size was . I believe its 32-34
Le Mans Master
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From: Cool Northern Michigan
So, a spacer will need to be added under the carb base for clearance.
Not a big deal on any other vehicle but with C3s hood clearance it is a . . . . . . . . .
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Originally Posted by brassplyer View Post
Should I need anything but the 50cc diaphragms? I see there are "conversion kits" - should the diaphragm just be a drop-in to my current setup?
Should I need anything but the 50cc diaphragms? I see there are "conversion kits" - should the diaphragm just be a drop-in to my current setup?
So, a spacer will need to be added under the carb base for clearance.
Not a big deal on any other vehicle but with C3s hood clearance it is a . . . . . . . . .
Le Mans Master
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Ok. But you still have a carb pad to mount the carb. Isn't that blower the same clearance as a Intake Manifold? IDK
Those bigger diaphragms have a slightly longer stroke to the pump arm.
Those bigger diaphragms have a slightly longer stroke to the pump arm.
