Holley accelerator pumps/cams



Holley accelerator pumps/cams

Postby grumpyvette » June 8th, 2009, 7:54 am

HOLLEY ACCELERATOR PUMP CAMS
heres a needle and seat fuel valve
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Here's a picture, Double Pumper on the left, Vacuum secondary on the right... Note on the upper left of each carb, the DP has linkage attached to the base plate/throttle shaft that actuates the secondary pump lever... The Vacuum carb has the large vacuum pod on the upper left side of the carb...
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THE O-RING ON THE NEEDLE AND SEAT, AND THE DIAPHRAGM IN THE ACCELERATOR PUMP, CAN BE DAMAGED BY ETHANOL IN FUEL UNLESS AN ETHANOL COMPATIBLE MATERIAL IS USED
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YOU REALLY SHOULD WATCH THESE SHORT VIDEOS

http://www.youtube.com/watch?v=k-Nx5HEz ... _embedded#!

http://www.youtube.com/watch?feature=pl ... -Nx5HEzvlY

https://www.youtube.com/watch?v=k-Nx5HEzvlY

http://www.youtube.com/watch?v=tMKxD_OFuCA

http://www.youtube.com/watch?v=eiRIfcrc2yA

http://www.youtube.com/watch?v=eiRIfcrc ... _embedded#

http://www.youtube.com/watch?v=k-Nx5HEzvlY

READ THESE RELATED THREADs /LINKS


viewtopic.php?f=32&t=6011&p=18597#p18597

http://www.stockcarracing.com/techartic ... index.html

viewtopic.php?f=55&t=5229

http://www.quickfueltechnology.com/tech ... -continued

viewtopic.php?f=55&t=1639

viewtopic.php?f=55&t=109

viewtopic.php?f=70&t=202

viewtopic.php?f=70&t=4683

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http://store.summitracing.com/partdetai ... toview=sku
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http://store.summitracing.com/partdetai ... toview=sku
http://store.summitracing.com/partdetai ... toview=sku
http://store.summitracing.com/partdetai ... toview=sku
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Holley Accelerator Pump Cam Chart (above)

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Holley Accelerator Pump Cam Chart , INDEPENDENT TESTING DONE, notice its NOT an exact match to what HOLLEY tech guys posted
[b]don,t forget the accelerator pump itself can be upgraded from 35cc to a 50cc version on many holley carbs[/b]

http://www.stockcarracing.com/techartic ... index.html

http://www.holley.com/types/Accelerator ... 0Parts.asp

http://www.holley.com/types/Accelerator ... 0Parts.asp



This chart gives the pump shot volume in CCs for each cam in each position.

Position 1 Position 2
White 17 19.5
Blue 18 20
Red 18.5 20
Orange 19 24
Black 19 18
Green 24 30
Pink 30 37.5
Brown 36
http://store.summitracing.com/partdetai ... toview=sku

don,t forget the squirters or Accelerator Pump Discharge Nozzles
They come in 3 different types. Straight - anti pullover - and tube types. and different sizes

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anti pullover
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Straight
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tube types.
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the accelerator pumps shot should hit the lower edge of the booster nozzle for better atomization, so the squirter you've selected should in part depend on the type of booster, accelerator pump volume and the distance from squirter to that booster, the type of squirter used should also depend on the pump volume and carburetor vacuum readings as exceptionally high plenum vacuum can draw fuel from the squirters. the anti pull over design is just needed for special applications like using a 2 barrel or a small 4 barrel on a larger displacement V-8 where the plenum vacuum is strong enough at WOT suck fuel from the squirter , occasionally causing a over rich condition


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http://www.summitracing.com/parts/MOR-65222/?rtype=10

http://store.summitracing.com/egnsearch ... toview=sku

http://store.summitracing.com/egnsearch ... toview=sku

http://holley.com/data/TechService/Tech ... 20Info.pdf
(READ PG 4)

http://www.automedia.com/Holley_Carbure ... 000718hm/1

http://www.nationaltbucketalliance.com/ ... /carbs.asp

You generally select a power valve thats 1/2 the vacuum at idle , example if your pulling 17" at idle you select a 8.5-or 9.5 power valve, if your pulling 12" you select a 5.5 -6.5 power valve, your running about 5" so youll want a 2.5 -3.5 power valve AS A START POINT THEN TUNE UP OR DOWN IN F?A RATIO AS REQUIRED READING PLUGS OR USING A F/A RATIO METER ON THE EXHAUST
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http://www.summitracing.com/parts/HLY-20-12/
http://www.summitracing.com/parts/HLY-125-25/
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If your tuning a holley carb having the 50cc accelerator pump kit and a selection of accelerator pump cams, a set of jets, squirters,and power valves in your tool box and a decent vacuum gauge, to tune with is a big help at times
Ive generally found the BLUE ACCELERATOR PUMP cam to be the best choice in most applications once the jets and power valves are correct
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: Holley accelerator pumps/cams

Postby grumpyvette » March 17th, 2013, 10:10 am

http://www.summitracing.com/parts/hly-135-7/overview/ 50CC-GAS
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BLACK RUBBER ACCELERATOR PUMP DIAPHRAGMSs ARE DESIGNED FOR 100% GAS
THESE BLACK ACCELERATOR PUMP DIAPHRAMS THAT CAME AS ORIGINAL EQUIPMENT IN MOST OLDER HOLLEY CARBS WILL EVENTUALLY FAIL WITH FUEL CONTAINING ALCOHOL

http://www.summitracing.com/parts/hly-135-9/overview/ 50CC-GAS ALCOHOL
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BLACK & GREEN ACCELERATOR PUMP DIAPHRAGMSs ARE DESIGNED FOR ALCOHOL/GAS FUEL MIXED


http://www.summitracing.com/parts/hly-135-5/overview/ 30CC-GAS
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http://www.summitracing.com/parts/hly-135-10/overview/ 30CC-GAS ALCOHOL
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Q: I can’t get the “Bog” out of my mechanical secondary carburetor what’s wrong and how can I fix it?

The sole purpose of the accelerator pump system is to provide a combustible air/fuel ratio during hard acceleration, especially from idle, for the time it takes the main metering system, via the booster venturi, to respond to the increase in air velocity. When you mash the throttle opening the throttle plates, air responds instantaneously to the pressure drop (vacuum) generated by the engine through the intake manifold. Fuel on the other hand is too heavy and cannot respond as the air does. Assisting the engine during this transition carburetor engineers developed a hydraulic fuel delivery system to push fuel into the slug of incoming air to make a combustible mixture.

The accelerator pump system is simply a mechanical fuel injector that provides enough fuel for a brief period of time for the engine to respond smoothly to the heavy wide open throttle demand. Its purpose is oh so simple and its function is oh so critical. And, when it isn’t working right, the dreaded “Bog” and the always dreaded backfire through the carburetor are effects of an accelerator pump system that isn’t equal to the task. The “Bog” simply means the engine is not receiving enough fuel when you go to wide open throttle. While there are other issues that may cause similar reactions within the carburetor, often the problem can be traced back to the accelerator pump system.

Incorrect adjustment is the typical culprit. The accelerator pump function, as mentioned, is based on hydraulic principles. Therefore, it is essential that the accelerator pump always has tension at your normal idle position. Any air gap here will delay the actuation of the accelerator pump system allowing air to rush into the engine without fuel.

The common misconception is that it is necessary to adjust the pump arm to obtain an air gap. This is correct; however that air gap is only at Wide Open Throttle (W.O.T.) not at idle. The air gap is simply to ensure additional travel in the pump arm so it does not bottom out on the fuel bowl. If it does bottom out eventually it could loosen the accelerator pump housing causing a fuel leak. Fuel leaks are something we all want to avoid.

Assuming the first adjustment is correct. Then the next step in the process is to add more fuel to the incoming air which is accomplished by increasing the size of the pump discharge nozzle or squirter. This will quite often correct the “Bog” or hesitation by richening the air/fuel mixture when the pump system is activated. If the carburetor works well everywhere else on the track then a bigger squirter might be the only change necessary.

Pump squirters are available in a wide range of sizes, the bigger the number (size) the more fuel when you accelerate. Simply remove the pump nozzle screw, lift off the old nozzle and install the new. Be sure both gaskets above and below the nozzle are replaced. If the gaskets are a different thickness the thicker goes under the nozzle and thinner one on top.

Q. How do I know if I need a bigger pump, i.e. a 50cc versus a 30cc?

A larger capacity accelerator pump achieves one thing, it extends the duration of the pump shot. A larger accelerator pump is usually required when the carburetor, intake manifold and/or cylinder head is too large for the engine and the resulting weaker signal at low engine RPMs requires more time for the booster venturi to pull fuel through the main jet. Generally, the telltale sign is good initial throttle response, but shortly thereafter the engine bogs down or flat lines and as the RPM climbs it recovers accelerating normally. That bog or flat spot is where the pump shot duration ran out and the booster venturi fuel flow alone is not enough to keep the engine running efficiently. In this case, the larger pump capacity helps the transition. While this is a more popular change among foot brake cars, the 50cc is also sometimes a necessity with large plenum 2 X 4 tunnel ram applications especially when racing on a .400 Pro Tree.

By the way for you curious types, the 30 and 50cc capacity is the volume of fuel displaced from the accelerator pump in 10 complete strokes of the pump arm. So the actual capacity is 1/10 that number or roughly 3 and 5cc respectively when opening the throttle from idle to wide open.

The larger capacity 50cc pump is easily recognizable by the large pump arm with the encapsulated spring. In addition, the 50cc pump also uses a larger pump cam either a brown color (conventional carbs) or a yellow color (model 4500).

A 50cc pump will not deliver the 50cc rated volume if any other cam is installed.




[b]WATCH VIDEOS

https://www.youtube.com/watch?v=X2W0blhIrug

https://www.youtube.com/watch?v=SQIQdsAnnA0

https://www.youtube.com/watch?v=kz7oZbtB3S8

https://www.youtube.com/watch?v=Y3hZrW4Ryo4

https://www.youtube.com/watch?v=k-Nx5HEzvlY

https://www.youtube.com/watch?v=47A6_LF295o
these pictures may be helpful
[/b]

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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida


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