Accelerator pumps
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Accelerator pumps

  1. #1
    I'm No Expert Shaun's Avatar
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    Default Accelerator pumps

    On a set of holley 4150/4160's what type of lash should i have between the linkage and the accelerator pump?

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    Quote Originally Posted by Shaun View Post
    On a set of holley 4150/4160's what type of lash should i have between the linkage and the accelerator pump?
    ur prob gonna get alot of answers to the ??...i think the book says about .015 with the primaries wide open!...i also think every1 sets there's different

    FastRat

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    I'm No Expert Shaun's Avatar
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    If you watch this video, when i jump on the throttle you can hear the boat hickup. Only two things where done to the carbs when this started, one thing was that the screw that holds the secondarys when close was turned out alittle bit to close the secondarys alittle bit more. This was done because once i fixed my vacum leak i ended up with a high idle, from what i understand the secondarys where open too much so the idle circuit was no longer being used. The other thing that was adjusted was the lash was set to 0 on the acc pumps.

    I'm no carb genious but what i'm guessing is happening is that when i jump on the throttle fuel is being dumped into the carb but the butterflys are not opening up enough yet? dont know, was just my guess.

    So i need to pull the throttle linkage so that the butterflys are wide open and then set the lash? WOuldnt the acc pump be pressed in?

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    I'm No Expert Shaun's Avatar
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    Driver 78CoLeBBF's Avatar
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    is the lash the same on a dominator 1050 also for the acc. pump sorry for jacking your thread shaun
    Its a FORD thing chevy's arent quick enough to understand

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    Quote Originally Posted by 78CoLeBBF View Post
    is the lash the same on a dominator 1050 also for the acc. pump sorry for jacking your thread shaun
    i would think so...i'm told that u want a smooth response with no hesitation or bog when u slam the throttle from idle

    FastRat

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    Quote Originally Posted by Shaun View Post
    If you watch this video, when i jump on the throttle you can hear the boat hickup. Only two things where done to the carbs when this started, one thing was that the screw that holds the secondarys when close was turned out alittle bit to close the secondarys alittle bit more. This was done because once i fixed my vacum leak i ended up with a high idle, from what i understand the secondarys where open too much so the idle circuit was no longer being used. The other thing that was adjusted was the lash was set to 0 on the acc pumps.

    I'm no carb genious but what i'm guessing is happening is that when i jump on the throttle fuel is being dumped into the carb but the butterflys are not opening up enough yet? dont know, was just my guess.

    So i need to pull the throttle linkage so that the butterflys are wide open and then set the lash? WOuldnt the acc pump be pressed in?
    Shaun...
    we could prob use a little more info ie: motor sz, intake ur running, carb sz ur useing, linkage set-up

    FastRat

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    Quote Originally Posted by Shaun View Post
    On a set of holley 4150/4160's what type of lash should i have between the linkage and the accelerator pump?
    Hey Shaun, If you had to close off the secondary b/flys to get the motor to idle down then you also closed off a feul supply. If now with that being done and you developed a stumble at throttle then the motor is saying need feul. Before I go any further you should have zero lash on the squirter lever at closed throttle. Someone may have cracked the secondary plate to eliminate this problem prior. You want a squirt of feul at first movement of the throttle. adjust the acctuator lever so this is acomplished. If you still have a stumble then look at the primary shooter and get a number. You did not reference a size of carb but most holleys in the 4150 and 4160 series are out of the box with a 25-31 squirter. Step it up a notch. Most Holleys are set to a base line for a relatively stock manifold. Then you add a larger manifold with more plenum and air and the initial shock must be adjusted to add the feul to match the enlarged plenum area, Larger squirter!!. M

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    Quote Originally Posted by Shaun View Post
    On a set of holley 4150/4160's what type of lash should i have between the linkage and the accelerator pump?
    Straight from Holley:

    First you will need to check the adjustment on the pump. To do this you will open the throttle all the way (WOT). Push the pump arm lever down and then adjust the pump override spring to obtain .015" clearance between the pump arm and lever. If you are having a stumble and no black smoke out the tailpipe then you will need to increase the shooter size. If it stumbles and you are getting black smoke from the tailpipe then it will be nessasary to decrease the shooter size.

    The adjustment in bold is to insure the pump is not dmaged at WOT (still has a tiny ammount of unused travel) or the diaphram can get torn. The actuatior arm shoudl be resting on the cam at idle and pump shot should be instantaneous on the smallest throttle movement.
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    I'm No Expert Shaun's Avatar
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    468 BBC, 10.25 comp, solid roller valve train, cam by chris straub, msd pro bil, msd 6al, blaster 2, edlebrock tr2x manifold, dual carbs, they are 660 center squirters that where rebuilt by bigs performance. Idle circuit was shrunk, secondary metering plate was converted to a metering block, jets are 74's in primary and secondarys. Primary shooter is .025.

    The stumble happens at any RPM but only when i mash the throttle! It doesnt do it if i bump from say 3000 rpm to 4500 rpm, it's only when i go for WOT.

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    I'm No Expert Shaun's Avatar
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    if you want more info or details on the motor check out my build thread.

    http://hotboat.com/forums/showthread.php?t=126180

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    The clearance between the pump arm and the diaphragm is there so you don't bottom out the diaphragm at WOT. Ther should be no clearance at closed throttle...like old said, you want instant fuel at the slightest throttle movement. At WOT, as long as you can still move the little lever on the pump diaphragm cover, you're OK. If not, the diaphragm is bottomed out and you need to adjust the spring loaded screw on the pump arm until you can, and can move it a blout .020-.030 inch.

    The difference in squirter nozzles isn't for a greater or smaller amount of fuel when you open the throttle, it changes the duration of the shot. Big squirter, big, quick shot. Smaller squirter, less fuel over a longer duration. Different effects for different tuning. Both give the same amount of fuel...one stroke of the pump is one stroke...same volume of fuel every time.

    There is one case where you want clearance between the accelertor pump arm and the squirter lever at closed throttle, but that's another thread.
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    gn7
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    Quote Originally Posted by steelcomp View Post
    The clearance between the pump arm and the diaphragm is there so you don't bottom out the diaphragm at WOT. Ther should be no clearance at closed throttle...like old said, you want instant fuel at the slightest throttle movement. At WOT, as long as you can still move the little lever on the pump diaphragm cover, you're OK. If not, the diaphragm is bottomed out and you need to adjust the spring loaded screw on the pump arm until you can, and can move it a blout .020-.030 inch.

    The difference in squirter nozzles isn't for a greater or smaller amount of fuel when you open the throttle, it changes the duration of the shot. Big squirter, big, quick shot. Smaller squirter, less fuel over a longer duration. Different effects for different tuning. Both give the same amount of fuel...one stroke of the pump is one stroke...same volume of fuel every time.

    There is one case where you want clearance between the accelertor pump arm and the squirter lever at closed throttle, but that's another thread.
    Don't stop there Steel. Shaun if it hiccups from idle when you stab it, you are going to need a larger shooter nozzle, but with 660's that can be a bitch to pull off easily. A smaller plenum on the TR would help, but that's no beginner fix either. Make certain you have 50cc pumps for starters. If it only hiccups from part throttle on, then you can increase the pump shot by delaying the shooter by adding lash to the pump lever, but I dont recommend this unless that is the only place it stumbles, because it will only make an off idle stumble worse. Drag cars with Hi stall converters do this so they have the whole pump shot on the launch with the throttle part way open when they stage. You may want to buy a couple of pump cam kits and and play with different pump timing to get rid of the hiccup. 660's were never intended for part throttle driving, floor it and go. GOOD LUCK



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  16. #14
    I'm No Expert Shaun's Avatar
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    The hickup only happens when punching it to WOT. I cant really remember rigth now if it does it from a idle because i dont normally hammer WOT from idle, my impeller is cavitating quiet a bit right now. From a cruising speed though if i hammer WOT then it does the hickup you hear in the video... it's a pretty big one, you cant miss it.... almost sounds like i jumped on the throttle got off it and jumped back into it.

    gn7 you said to make sure i have 50cc pumps, how do i check this, i'm not really too fermiliar with the carb and all it's parts...

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