Accelerator pump cam question about holley

Accelerator pump cam question about holley

Joined: September 22nd, 2008, 10:06 pm

January 22nd, 2012, 3:05 pm #1

Just bought a 750 3310 vac secondary holley for my 400. Getting a slight hesitation out of the hole at wot. Noticed it came stock with a dark green accelerator pump cam. Looks like the thottle moves a bit before and gas comes out of squirters and the pump arm is contacting the pump lever as it starts to move when touched. I thought all stock holleys came with a pink cam. It has .031" shooter in it stock. What are most of you using for pump cams? Thanks
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Joined: December 17th, 2003, 4:14 pm

January 22nd, 2012, 5:08 pm #2

with the set screw, the cams can be moved around by the mounting screws also.
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Joined: December 16th, 2003, 1:59 am

January 22nd, 2012, 7:01 pm #3

the procedure calls for checking for clearance between the pump arm and adjuster at full throttle, you can actually be well into the pump at idle and still have a full fuel shot & recommended clearance at WOT

the point is to not be stretching the diaphragm at WOT, rupturing one will cause an external leak onto the intake manifold

there'll be phantoms, there'll be fires on the road... and the white man dancing
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Joined: June 23rd, 2010, 4:42 am

January 22nd, 2012, 10:03 pm #4

Just bought a 750 3310 vac secondary holley for my 400. Getting a slight hesitation out of the hole at wot. Noticed it came stock with a dark green accelerator pump cam. Looks like the thottle moves a bit before and gas comes out of squirters and the pump arm is contacting the pump lever as it starts to move when touched. I thought all stock holleys came with a pink cam. It has .031" shooter in it stock. What are most of you using for pump cams? Thanks
Yeah I always thought/seen the pink cams on performance carbs(new). The green cam is the most aggressive one (large initial shot, not total volume), it's what I use on the primary of my DP. Large cam and large intake plenum equals lots of fuel from the primary accelerator pump. I havent seen much benefit from changing squirters, but definitely the cams are the main tuning aid. Why not pull the cam out and verify the number on it, if it is a 290/green then you are probably too rich depending on cam/intake. Purchase an assortment pack and try some other cams.

There will always be a slight lag between throttle and pump discharge starting out from the closed position for the most part, but should not be excessive.

As previously mentioned, just make sure there is not free play on the arm and the cam.
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Joined: September 22nd, 2008, 10:06 pm

January 22nd, 2012, 11:46 pm #5

It is the 290 green pump cam that came in it from the factory. I have another old junk 3310 that is about 3yrs old that came with a orange cam from the factory. There is no slack between the pump and arm. I have a pink and orange cam that i can try that was on the old carbs i have. From what i read the pink cam has the most shot volume, is that right? I thought i may try the pink one first. The intake is offenhauser dual port and cam is a lunati voodoo 262 with 219/227 dur at .05" lift.
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Joined: December 17th, 2003, 4:14 pm

January 23rd, 2012, 12:21 am #6

going with more shot or bigger shooters can make the stumble worse. try the pink cam, it may shoot more volume, but it is stretched out over more throttle opening. If it still isn't right, try a smaller shooter. This goes against all other intake advice, because of the small plenum and runner volume of the Dual Port. This was about 12 years ago when I tuned a 351 4v.
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Joined: June 23rd, 2010, 4:42 am

January 23rd, 2012, 2:21 am #7

It is the 290 green pump cam that came in it from the factory. I have another old junk 3310 that is about 3yrs old that came with a orange cam from the factory. There is no slack between the pump and arm. I have a pink and orange cam that i can try that was on the old carbs i have. From what i read the pink cam has the most shot volume, is that right? I thought i may try the pink one first. The intake is offenhauser dual port and cam is a lunati voodoo 262 with 219/227 dur at .05" lift.
Why they stuck a green cam in their IDK...
The pink and the orange are very close to each other(initial shot wise), the pink has more volume.. bad gas mileage(generally).. generally dont need a long shot, try the orange and if it works keep it!!

With the small cam/intake sounds rich to me!
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Joined: September 22nd, 2008, 10:06 pm

January 23rd, 2012, 4:43 am #8

I have never seen one with a green cam stock. When i took it out of the box i thought what the heck thats not what nomally comes in them. Why would holley do that? Could that be a new revision on that model of carb? I ran a 600 holley with a pink cam before and had no problems and also ran a 670 holley with the orange cam and had no problems. So my logical thinking was to use one that worked on another carb on the same engine. I went out earlier and bolted in the pink cam to try first. It may be a day or so till i can may a test run though. Thanks for the help. I'll keep you all posted. Thanks again.
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Joined: June 23rd, 2010, 4:42 am

January 23rd, 2012, 6:57 am #9

No one set-up is the same from one car to another, this is why we have to tune them!
Roo might be right the pink is the deal! My opinion is a carb is an imperfect device, never right in all circumstances. So figure out where you want the car to run the best and tune for that!

A side note: If the car is rich out of the hole, then lean(in your case my opinion).
If you then have a high rpm stumble, like a highway thing, then couid be it's to lean, not enough pump duration, so swap in the pink.

Let us know.
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Joined: December 16th, 2003, 1:59 am

January 23rd, 2012, 8:00 pm #10

bump up the primary jets & tune the pump cam/shooter back down

there'll be phantoms, there'll be fires on the road... and the white man dancing
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