|06-23-2012 01:46 PM|
It doesn't need a 50cc pump. The 50cc pump uses pump cams specific to it, not the usual 30cc cams. If you have any cams w/three positions and you are sure you have a 50cc pump, install that cam in position #3 and see if you have clearance. Otherwise you need 50cc cams.
IMO the best thing you could do is to tune the ignition advance, then put the 30cc pump diaphragm and cover back on it, w/the 30cc linkage, of course. Use a orange cam in position #1 and tune from there.
See post #49 for more on accelerator pumps.
|06-23-2012 10:39 AM|
like i was saying before my computer got weird. it is a 50cc pump as far as i can tell all the right linkage is there and it isn't bent. i finally found my vacume gauge and am going to check it that way. i will let you know how that goes.
|06-23-2012 02:55 AM|
Is there a chance you have a 50cc pump on it w/the 30cc linkage?
30cc pump diaphragm, cover w/pump arm
Late style plastic linkage/adjuster screw assembly for 30cc pump
50cc pump diaphragm, cover w/pump arm, linkage specific to 50cc pump assembly
|06-23-2012 02:34 AM|
when carb is at WOT i cannot get any clearance on shaft no matter what i do. i have turned it up until spring was collapsed with no give and still can't get gauge to go between shaft and adjuster linkage. and when i go the other way it just gets tighter.
I really do appreciate the info. I have been able to use most of it. This carb may find its way to the lower 40, if you know what i mean. It just tears me up though for something to beat me. sometimes i need to quit but won't. LOL
|06-22-2012 10:39 PM|
The pump has to give a shot the instant the throttle is opened, and at WOT there must be at least 0.015" clearance between the pump arm and the linkage.
A couple things might be happening that is screwing the off idle response up.
First is the initial timing. That cam will no doubt have a lot of duration and overlap. This requires a LOT of initial timing.
This will mean the carb primaries will need to be open so far to get an idle that the carb is actually idling more on the transition slots than the idle circuit. By increasing the initial timing, the idle speed will increase. That allows the primary throttle blades to be closed back down, hopefully enough that the carb will be idling on the idle circuit and not on the transition circuit. If this is happening, the off idle transition will be poor.
You can check for this by seeing if the idle mixture screws change the idle or not. The engine should stall or nearly so when the screw is turned CW all the way. If the engine continues to run, you know the primary blades are open too far.
The other thing is, if the carb primaries do have to be opened real far, the accelerator pump cam should be installed in the #2 position. This will allow a full shot even w/the primary throttle shaft rotated open, because of how the #2holes position the cam.
|06-22-2012 09:18 PM|
been there done that
i have tried several different squirters and no help some even worse anything over .35 really bogs it down.
could the acc pump cam being on backwards have messed up the acc pump or ruptured the diaphragm?
|06-22-2012 09:04 PM|
Change the squirters and it should help you out. should have .31 go next step up to a .35 .JMO
|06-22-2012 08:59 PM|
spooky holley 3310c
I am about to go crazy with this holley. its a 3310c 750 street strip carb. i have it set to where the engine will idle. the motor is a 355 small block chevy, aluminum heads weiand single plane intake 10.5.1 comp, 550 hyd flat tappet cam, roller tip rockers. Idle is at 1300rpm. at first i had trouble with a bad hesitation when throtle was opened fast. finally figured that one out. pump cam was on backwards. now it will rev while in neutral with no hesitation. put it in gear build to 2000 or better with brake on hit the gas and it falls flat on its face. i am 62 yrs old and could out run it on foot for 60ft. its bad. doe anyone have a clue as to what may be wrong now. bottom of accelerator pump stays a little damp with gas. it is set at thousands and is real loose at idle.
when in neutral it has no hesitation and engine will hit 5000rpm in a heart beat but when in gear will barely pull itself.
like i said this is a spooky holley.