Another Holley Idle Thread - I'm at wit's end!
06-17-2010, 08:30 PM
#1
Registered
Thread Starter
Another Holley Idle Thread - I'm at wit's end!
I have been trying to get my 850 double pumper set up right, and I am baffled. I have read through every thread on the board, read a holley tuning book cover to cover, and I still can't get it right. I'll try to cover all the bases, so bear with me...
Specs:
468 cid
Performer RPM intake
CMI big E-tops
good performace roller cam, not insane. (don't have the specs in front of me)
Background:
The boat would start easily, and once it is warmed up, idles about 750RPM. If I put it in gear, the revs stay dead constant, but if i try to give it throttle too soon, it coughs through the carb and stalls. If I wait a few seconds for things to stabilize, I can give it throttle without any problems. If I stab the throttle, it hesitates, then jumps right on plane. If I feather it up really slowly, it will plane smoothly. If I try anything in between, i.e. a normal takeoff, it pops through the carb and stalls. Once over about 2800RPM, all is well.
The other piece to the puzzle is when slowing down, I have to pump the throttle several times to keep it running. If I chop it, it will die every time. If I bring it down slow, it dies. I always have to give it a pump shot to keep it alive. The faster I slow down, the more aggressive the shot has to be.
This all seems like a lean condition to me, so I started by pulling the carb off and overhauling it with a Holley kit, just to be sure everything was in fresh shape. The idle mix screws where turned way out, and the primary throttle stop was turned in 2 1/4 turns.
When I reset everything, I set the primary's to about 3/4 turn in, and the idle mix screws to 1 turn out. Set floats to bottom of plug. Seems no matter what I do, the symptoms remain the same. I have to crank the primary idle adjustment to at least 2 turns to maintain an idle, even if I open the secondary butterflies. Iv'e tried richening the idle 3+ turns, doesn't even seem to phase it.
It wraps up easily in neutral, and runs good everywhere else. Sorry for the long post, but I don't know what else to do short of packing it up and taking it to someone. I don't remember the last time I've been this stumped.
-Artie
Specs:
468 cid
Performer RPM intake
CMI big E-tops
good performace roller cam, not insane. (don't have the specs in front of me)
Background:
The boat would start easily, and once it is warmed up, idles about 750RPM. If I put it in gear, the revs stay dead constant, but if i try to give it throttle too soon, it coughs through the carb and stalls. If I wait a few seconds for things to stabilize, I can give it throttle without any problems. If I stab the throttle, it hesitates, then jumps right on plane. If I feather it up really slowly, it will plane smoothly. If I try anything in between, i.e. a normal takeoff, it pops through the carb and stalls. Once over about 2800RPM, all is well.
The other piece to the puzzle is when slowing down, I have to pump the throttle several times to keep it running. If I chop it, it will die every time. If I bring it down slow, it dies. I always have to give it a pump shot to keep it alive. The faster I slow down, the more aggressive the shot has to be.
This all seems like a lean condition to me, so I started by pulling the carb off and overhauling it with a Holley kit, just to be sure everything was in fresh shape. The idle mix screws where turned way out, and the primary throttle stop was turned in 2 1/4 turns.
When I reset everything, I set the primary's to about 3/4 turn in, and the idle mix screws to 1 turn out. Set floats to bottom of plug. Seems no matter what I do, the symptoms remain the same. I have to crank the primary idle adjustment to at least 2 turns to maintain an idle, even if I open the secondary butterflies. Iv'e tried richening the idle 3+ turns, doesn't even seem to phase it.
It wraps up easily in neutral, and runs good everywhere else. Sorry for the long post, but I don't know what else to do short of packing it up and taking it to someone. I don't remember the last time I've been this stumped.
-Artie
06-17-2010, 09:25 PM
#5
Registered
Thread Starter
I considered that, but it already has the big pump on it, and is still acts lean. If is it back at the carb, when it stumble, if I give it a shot of just the pump (no throttle) it recovers.
Timing is locked at 34*. Thats the way it came set up.
Timing is locked at 34*. Thats the way it came set up.
06-17-2010, 09:28 PM
#6
Charter Member #601
Charter Member
Been a long time also.. But look at the ramps for the Acc pumps, they are adjustable and different colors for more or less, aggressive.
Make sure the throttle plates on the primaries are in the middle of the idle slot.
When you move the throttle make sure there is no hesitation from the squirters..
Make sure the ports for the acc pump circuit is not blocked by a gasket or junk.
If you can slowly ease into higher rpms, and it doesnt cough, but when you do it at any rate, it has to be in the accelerator pump circuits.. Keep looking you will find it.
Dick
Make sure the throttle plates on the primaries are in the middle of the idle slot.
When you move the throttle make sure there is no hesitation from the squirters..
Make sure the ports for the acc pump circuit is not blocked by a gasket or junk.
If you can slowly ease into higher rpms, and it doesnt cough, but when you do it at any rate, it has to be in the accelerator pump circuits.. Keep looking you will find it.
Dick
06-18-2010, 01:38 AM
#8
Charter Member # 55
Charter Member
The 850 carb is on the large side for a 468. An 800 would have been much better.
Maybe a lack of vacuum at low rpms and the powervalve may be opening.
Are you setting the floats with the boat in the water????? The angle changes quite a bit sometimes and affects the adjustment.
Maybe a lack of vacuum at low rpms and the powervalve may be opening.
Are you setting the floats with the boat in the water????? The angle changes quite a bit sometimes and affects the adjustment.
06-18-2010, 08:25 AM
#9
Registered
Thread Starter
Been a long time also.. But look at the ramps for the Acc pumps, they are adjustable and different colors for more or less, aggressive.
Make sure the throttle plates on the primaries are in the middle of the idle slot.
When you move the throttle make sure there is no hesitation from the squirters..
Make sure the ports for the acc pump circuit is not blocked by a gasket or junk.
If you can slowly ease into higher rpms, and it doesnt cough, but when you do it at any rate, it has to be in the accelerator pump circuits.. Keep looking you will find it.
Dick
Make sure the throttle plates on the primaries are in the middle of the idle slot.
When you move the throttle make sure there is no hesitation from the squirters..
Make sure the ports for the acc pump circuit is not blocked by a gasket or junk.
If you can slowly ease into higher rpms, and it doesnt cough, but when you do it at any rate, it has to be in the accelerator pump circuits.. Keep looking you will find it.
Dick
The 850 carb is on the large side for a 468. An 800 would have been much better.
Maybe a lack of vacuum at low rpms and the powervalve may be opening.
Are you setting the floats with the boat in the water????? The angle changes quite a bit sometimes and affects the adjustment.
Maybe a lack of vacuum at low rpms and the powervalve may be opening.
Are you setting the floats with the boat in the water????? The angle changes quite a bit sometimes and affects the adjustment.
I have also checked everywhere for vacuum leaks.
Thanks all for the suggestions, I will be back on the water this afternoon trying to get it right again!
