G
Guest
·I've been reading like a g
I've been reading like a grad student, learning about sync procedures for our 308 carbs. I've read many different procedures, and understand the basic principles. I've identified the common points across everyone's carb sync procedure.
I'm currently struggling with one thing, though, and was looking for some help.
1. I know that the progression holes in the carbs are critical, since they help smoothen things out when transitioning from idle to off-idle.
2. I know that the throttle plates should just cover the first progression hole, so that the moment the plates are opened the progression holes become active.
3. I just had my carbs rebuilt by Pierce Manifolds. I checked, and I noticed the plates were configured to ALWAYS stop right where they were supposed to--at the first progression hole. A call to Mike Pierce at Pierce Manifolds confirmed this, this was done on purpose.
4. What I'm struggling with is, there's all this talk about setting the "Idle Speed Screw," which basically translates to moving the throttle plates and MODIFYING their relationship to the PROGRESSION HOLES (bad bad) in order to set your idle. I don't want to set my idle this way. My forming opinion, based on things that I've read, is that there is only ONE good position for the throttle plates, and that position is covering the first progression hole.
Point #4 was heavily influenced by an old thread I came across with Ferrari-Talk's own JRV as well as another knowledgeable carb person, Dr. Mike Adams.
Thanks to Hans Hansen for pointing out the merits of this logic as well as a few other more subtle points.
5. So it seems to me, therefore, that because my throttle plates are ALREADY set in their one perfect position in relation to the progression holes, I don't need to adjust the Idle Speed Screw aka Throttle Stop Screw on ANY of the carbs. For my purposes, they can be backed out or otherwise just touching the two carb throttle levers. Note that I'm also sensitive to the left/right linkage across the carbs, and have studied the mechanics of this and have found what I believe to be settings that leave all carbs throttle plates in their fully closed, "natural" positions.
Point #5 is the big one. Workshop manual and lots of folks say to adjust idle speed here. This is going to affect the fundamental carb response, because I'm messing with the throttle plates in relation to the progression holes.
Dr. Mike suggests that with this set, I can now leave the Idle Speed Screws ALONE and adjust the idle with the air balance / air bleed screws (which I'm not really proficient with at this point).
So before I go too crazy and sync the carbs with some fundamentally false assumptions, what are your thoughts on this logic?
If we can concur that this makes sense, I think we might be able to improve the carb response in many folks' 308s by syncing things differently than they have been synced in the past...
And finally, I defer any success this method may have to Hans Hansen, who had these new sync methods in mind well before I laid a hand on a carburettor.
Would be interested to hear comments on this, as well as ideas for how to set the idle speed with the air balance screws, and then also how the idle mix screws will play a role.
--Mike
I've been reading like a grad student, learning about sync procedures for our 308 carbs. I've read many different procedures, and understand the basic principles. I've identified the common points across everyone's carb sync procedure.
I'm currently struggling with one thing, though, and was looking for some help.
1. I know that the progression holes in the carbs are critical, since they help smoothen things out when transitioning from idle to off-idle.
2. I know that the throttle plates should just cover the first progression hole, so that the moment the plates are opened the progression holes become active.
3. I just had my carbs rebuilt by Pierce Manifolds. I checked, and I noticed the plates were configured to ALWAYS stop right where they were supposed to--at the first progression hole. A call to Mike Pierce at Pierce Manifolds confirmed this, this was done on purpose.
4. What I'm struggling with is, there's all this talk about setting the "Idle Speed Screw," which basically translates to moving the throttle plates and MODIFYING their relationship to the PROGRESSION HOLES (bad bad) in order to set your idle. I don't want to set my idle this way. My forming opinion, based on things that I've read, is that there is only ONE good position for the throttle plates, and that position is covering the first progression hole.
Point #4 was heavily influenced by an old thread I came across with Ferrari-Talk's own JRV as well as another knowledgeable carb person, Dr. Mike Adams.
Thanks to Hans Hansen for pointing out the merits of this logic as well as a few other more subtle points.
5. So it seems to me, therefore, that because my throttle plates are ALREADY set in their one perfect position in relation to the progression holes, I don't need to adjust the Idle Speed Screw aka Throttle Stop Screw on ANY of the carbs. For my purposes, they can be backed out or otherwise just touching the two carb throttle levers. Note that I'm also sensitive to the left/right linkage across the carbs, and have studied the mechanics of this and have found what I believe to be settings that leave all carbs throttle plates in their fully closed, "natural" positions.
Point #5 is the big one. Workshop manual and lots of folks say to adjust idle speed here. This is going to affect the fundamental carb response, because I'm messing with the throttle plates in relation to the progression holes.
Dr. Mike suggests that with this set, I can now leave the Idle Speed Screws ALONE and adjust the idle with the air balance / air bleed screws (which I'm not really proficient with at this point).
So before I go too crazy and sync the carbs with some fundamentally false assumptions, what are your thoughts on this logic?
If we can concur that this makes sense, I think we might be able to improve the carb response in many folks' 308s by syncing things differently than they have been synced in the past...
And finally, I defer any success this method may have to Hans Hansen, who had these new sync methods in mind well before I laid a hand on a carburettor.
Would be interested to hear comments on this, as well as ideas for how to set the idle speed with the air balance screws, and then also how the idle mix screws will play a role.
--Mike