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tried to use a magnet to pick up the debris we saw...not clearly metallic...nothing on the magnet. TBarb, i'll check on that, but wouldn't that exhibit a problem all of the time, not jsut from a cold start up? thanx. s
It may or may not, still got to rule it out. All a process of elimination, disconnect the secondary throttle shaft to eliminate that after you work past the choke mechanism.
tried to use a magnet to pick up the debris we saw...not clearly metallic...nothing on the magnet. TBarb, i'll check on that, but wouldn't that exhibit a problem all of the time, not jsut from a cold start up? thanx. s
The magnet's failure to pick up the debris doesn't prove that the debris is not metallic, just that it's not magnetic. The magnet would not pick up zinc or aluminum, for examples.
Yes, of course, the debris could be just dust or who knows what. Drove the car yesterday and the ambient temp was significantly cooler than it has been. Parked the car while i worked, went out there to go home and again, the throttle arm was "stuck", as it has been sitting overnight. Here's a picture of the fast idle cam, taken after work, when cold and stuck...sitting at the top of the steps. My wife inadvertently stepped on the gas pedal before I could watch carefully, so not sure what happened when it loosened up, but the fast idle cam didn't move. Car started great, fast idle appropriately in play, tho' I didn't look at the carb once the car started. Drove home: excellent. Once at home, the fast idle mechanism was in the same place as it had been when the throttle was stuck (top step).
with the car still hot from the drive home, i dc'd the choke rod from the thermostatically controlled coil. Went out there this AM: throttle stuck, as predicted, disconnecting the choke rod made no difference and the fast idle cam remained on the top step, as it was when i closed shop last night. So, i've got some info, but not sure what to do with it! Move on to dc'ing the secondary linkage as suggested by TBarb? thanx s
Here’s my next thought. Primary throttle plate binding when cold. Reasoning:
1. When the carb is warm, the plates move freely.
2. As the carb cools, the choke is off and the carb body contracts just enough to catch the plate.
3. When you depress the accelerator pedal, it frees the plate and the choke holds it open just enough to keep it free.
4. Once warm, it doesn’t stick as the interference is gone.
Something to try. Loosen all four carb mounting bolts. Retorque them in three steps in a crisscross pattern to a final torque of 70-80 inch/lbs.
when the engine is completely cold and you press all the way down on the throttle you are into the "choke unloader" which causes some extra resistance
Clem, this is more of a lock up situation that requires a hard stab onto the throttle to free it up. The fast idle arm rides above the fast idle cam, a slight adjustment to this arm frees it up.
Hmmm, throttle was bound when I go back to it today, I thought the fast idle arm was getting stuck on top of the fast idle cam, that's not the case, the step cam moves freely of the arm. Will report back tomorrow.
OK, took the carb off the car so I could get a better idea about what the heck is going on. I believe that the small, curved/bent rod that links the primary throttle mechanism to the secondary shaft (on the left side of the carb) was causing my problem. By bending and straightening that linkage rod mechanism, the primary now moves easily and freely. Have yet to drive the car, but it seems like a good start, as, on the bench, the accelerator arm moves perfectly. thanx so much. steve
(I can post a picture if anyone is interested...just need to move to another computer)
OK, took the carb off the car so I could get a better idea about what the heck is going on. I believe that the small, curved/bent rod that links the primary throttle mechanism to the secondary shaft (on the left side of the carb) was causing my problem. By bending and straightening that linkage rod mechanism, the primary now moves easily and freely. Have yet to drive the car, but it seems like a good start, as, on the bench, the accelerator arm moves perfectly. thanx so much. steve
(I can post a picture if anyone is interested...just need to move to another computer)
that rod is what closes the secondary after they are opened by vacuum
In pulling the secondary's closed it also secures them firmly closed at idle. I noticed when I recently rebuilt my Holley and was re-assembling it, that link needed to be adjusted as it wasn't securing the secondary blades fully closed at idle. On my 3247, the primary linkage kind of goes a little over center on it's end of the link when the throttle is closed which locks the secondary's down as long as the link goes all the way to the end of the slotted cam.
From my research I just want to add to the information about the secondary closing link.
I always thought the same as Dan about the link holding the secondary blades closed at idle but that's not it's purpose. When lifting the throttle the link will mechanically close the secondary blade but the air above at atmospheric pressure will force them closed at idle because the blade area is offset.
The secondary link is adjusted correctly when at 1/3 to 1/2 primary throttle blade opening the link allows the secondary blades to be open approx the same amount as the primary blades. At this point, both the primary and secondary blades will continue to open the same amount all the way to WOT. When adjusted like this there will be some play in the link at idle, remember the air against the offset blade keeps the secondary blades closed at idle.
This will ensure that when the secondary blades open they are held against the link and open equally with the primary blades, that is the desired effect when the secondary is tuned correctly.
From my research I just want to add to the information about the secondary closing link.
I always thought the same as Dan about the link holding the secondary blades closed at idle but that's not it's purpose. When lifting the throttle the link will mechanically close the secondary blade but the air above at atmospheric pressure will force them closed at idle because the blade area is offset.
The secondary link is adjusted correctly when at 1/3 to 1/2 primary throttle blade opening the link allows the secondary blades to be open approx the same amount as the primary blades. At this point, both the primary and secondary blades will continue to open the same amount all the way to WOT. When adjusted like this there will be some play in the link at idle, remember the air against the offset blade keeps the secondary blades closed at idle.
This will ensure that when the secondary blades open they are held against the link and open equally with the primary blades, that is the desired effect when the secondary is tuned correctly.
10-17-2018, 09:49 AM
