mark_hagen
New member
First thread – long thread.
I apologize upfront for this long post. I have been pretty much self-sufficient this far into our 6-year father/son project, but now I am stuck. I have a 67 Mustang coupe with 200ci that I cannot get to idle, in order to set the idle mixture on the Weber Carb.
Here’s what I have;
200ci, .030 over, zero decked block
Weber 38 DGES carb
Classic Inlines modified 2V log, ported, polished, V8 valves
Clay Smith hydraulic cam (I think it is a 264/264 -112…..can’t find the paperwork on it)
HEI ignition
Weber fuel pressure regulator
AC mech fuel pump
Here is what is happening;
Per Weber’s instructions, the idle speed screw is tightened to just make contact with butterfly linkage (zero lash), and then turned ½ turn, maximum. This ensures that the carb is only running on the idle circuit and not getting any fuel from the enrichment holes or secondary circuit). The car is started and warmed up until the choke is fully open. When the accelerator pedal is released, the motor will only turn 400 to 500 rpm, and then quits. I cannot get the car to idle with only ½ turn of the idle speed screw. The car will not idle until the screw is at least 1 ½ to 2 turns; which is beyond the point where the butter fly plate movement has uncovered the enrichment holes (no longer idle circuit only). No matter how I try to tune it, I cannot get a proper idle with only ½ turn of the idle speed screw (which the Redline-Weber tech folks swear is the point where the motor should idle fine for idle mixture settings). Once the idle speed screw is turned 1 ½ to 2 turns, the engine runs fine around 750-800 rpm, even with the AC on. The idle vacuum is around 15”, which is a little lower than I expected. I was also expecting a little more overall power than we are getting, considering the mods we have done, but that is hard to quantify at his point.
Here is what I have done;
Checked for vacuum leaks; sprayed cleaner around base of carb and carb fittings to check for increase in idle rpm. All seals are good. Sealed off port leading to brake booster. Replaced already-new PCV valve with new-new PCV valve. Checked PVC hose and connections. I have pulled, cleaned and inspected the carburetor at least three times. Thinking that I was not getting enough fuel, I changed out the original .400mm idle jets for .050mm, then went to .055mm, then to .060mm, and still no change. I have tried various timing settings with some success in getting the minimum controllable idle speed a little higher, but the engine still quit as soon as I got close to ¾ to 1 turn of the idle speed screw.
My other thought was to check the cam timing, but I cannot find the paperwork from when I purchased the cam from Mike, 2 years ago. I’m afraid I will have to pull the can just to see what model it is, before I can do anything about the timing, unless there is a way to get at old invoices from Classic Inlines.
I am open to any suggestions that anyone may have, as I am at the end of my limited expertise.
Thank you in advance.
-Mark
I apologize upfront for this long post. I have been pretty much self-sufficient this far into our 6-year father/son project, but now I am stuck. I have a 67 Mustang coupe with 200ci that I cannot get to idle, in order to set the idle mixture on the Weber Carb.
Here’s what I have;
200ci, .030 over, zero decked block
Weber 38 DGES carb
Classic Inlines modified 2V log, ported, polished, V8 valves
Clay Smith hydraulic cam (I think it is a 264/264 -112…..can’t find the paperwork on it)
HEI ignition
Weber fuel pressure regulator
AC mech fuel pump
Here is what is happening;
Per Weber’s instructions, the idle speed screw is tightened to just make contact with butterfly linkage (zero lash), and then turned ½ turn, maximum. This ensures that the carb is only running on the idle circuit and not getting any fuel from the enrichment holes or secondary circuit). The car is started and warmed up until the choke is fully open. When the accelerator pedal is released, the motor will only turn 400 to 500 rpm, and then quits. I cannot get the car to idle with only ½ turn of the idle speed screw. The car will not idle until the screw is at least 1 ½ to 2 turns; which is beyond the point where the butter fly plate movement has uncovered the enrichment holes (no longer idle circuit only). No matter how I try to tune it, I cannot get a proper idle with only ½ turn of the idle speed screw (which the Redline-Weber tech folks swear is the point where the motor should idle fine for idle mixture settings). Once the idle speed screw is turned 1 ½ to 2 turns, the engine runs fine around 750-800 rpm, even with the AC on. The idle vacuum is around 15”, which is a little lower than I expected. I was also expecting a little more overall power than we are getting, considering the mods we have done, but that is hard to quantify at his point.
Here is what I have done;
Checked for vacuum leaks; sprayed cleaner around base of carb and carb fittings to check for increase in idle rpm. All seals are good. Sealed off port leading to brake booster. Replaced already-new PCV valve with new-new PCV valve. Checked PVC hose and connections. I have pulled, cleaned and inspected the carburetor at least three times. Thinking that I was not getting enough fuel, I changed out the original .400mm idle jets for .050mm, then went to .055mm, then to .060mm, and still no change. I have tried various timing settings with some success in getting the minimum controllable idle speed a little higher, but the engine still quit as soon as I got close to ¾ to 1 turn of the idle speed screw.
My other thought was to check the cam timing, but I cannot find the paperwork from when I purchased the cam from Mike, 2 years ago. I’m afraid I will have to pull the can just to see what model it is, before I can do anything about the timing, unless there is a way to get at old invoices from Classic Inlines.
I am open to any suggestions that anyone may have, as I am at the end of my limited expertise.
Thank you in advance.
-Mark