Larger Shooter or Bigger Cam which first
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Need to cover up the bog/stumble on my Holley 750 I just installed. Im reading about adjusting the shooters up in size and changing the accel. pump cam to give more or less duration.. Which should I do first? Seems like I cant find anything in my 3 holley books I bought that tell you HOW to do this...They give good discriptions of the operation of each but mostly they all pretty much quote each outher and say "trial and error" Im assuming since my problem is pretty bad I should go the shooter route till I can make the transition without the stumble being so bad and then work the cam for duration...Am I thinking right here? Also at which point do you go with the 50cc pump? Their is really no process I can find anywhere that takes you step by step thru the process....The bog/stumble is VERY bad. I mean in gear if I hit it pretty hard the boat will almost or sometimes even stall! EASY on the throttle and once past the transition everything is fine. Matter of fact I gained a ton of power just switching over from the 600 "brock" I was using....Thoughts?
BH
BH
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I was reading somewhere that when using a larger than needed carb on a motor (750cfm on my 358sbc pushing 5300rpms) That this is when the need for more/longer pump shot is most needed. So I assume this is true. Comments? Bobby Im gonna order the 50cc pump for Jegs
BH
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I'm prob wrong, but i don't think the shooter is changeable on a 4010 holley.........
dumb question, but are you sure the accelerator pump is working properly?
again........ignore me if i'm wrong, just throwing ideas out there...
dumb question, but are you sure the accelerator pump is working properly?
again........ignore me if i'm wrong, just throwing ideas out there...
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One thing to look at is the position of the primary throttle plates, if they are set too far open (to get it to idle) then you may be off of the transfer slots.Remove the carb and flip it upside down .Look at the throttle plate (primary) and see how far it is opened .You will see little vertical slots in the aluminum part .The plates have to be below those or you will have a bad stumble or hesitation. There are a few ways that I know of to overcome this problem.
(1) lean the idle circuit by plugging the orifice and re drilling.
(2) drill .100 diameter hole through the primary throttle plate.
(3) some guys will adjust secondary throttle plates to allow air to leak by them ,you could try this pretty easily.
What # and style of shooter are you running?Also what ignition are you running and how much initial timing?
A larger cam likes more timing I run 18 degrees initial and 34 degrees total on my 406 .
PM Me if you have any other questions
Rob
(1) lean the idle circuit by plugging the orifice and re drilling.
(2) drill .100 diameter hole through the primary throttle plate.
(3) some guys will adjust secondary throttle plates to allow air to leak by them ,you could try this pretty easily.
What # and style of shooter are you running?Also what ignition are you running and how much initial timing?
A larger cam likes more timing I run 18 degrees initial and 34 degrees total on my 406 .
PM Me if you have any other questions
Rob
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My dad runs an 800 double pumper on his 358 chev. We had the same problems you are refering to. We added 50 cc pump to the primary and tube type squirters. We also locked the timing all in. Now it runs like a raped ape with no hesitation at all and comes out of the hole as fast as a Ski Nautique. Small blocks like a little more timing than BBC's. We run ours at 38 degrees and locking the timing in really helps. Is the 750 a marine carb or auto? Another factor is the accelerator pump cam duration and timing. Anyway I would follow Bobby D's advice and start with the 50 CC pump first. Good luck!!
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