C4 Kickdown rod linkage question (1966 V8 conversion)

[jnirenstein]

Merry Xmas! If you're tired of wrapping gifts, and putting up decorations....Feel free to chime in. I have converted a 1966 170 with 3 on the tree to a 289 (331 stroker) with a C4. The carburetor I'm using is a 1966 Autolite 4100 as would have appeared on a K code mustang or other 4V application in the day. I have a stock (I believe correct) kick down ROD attached to the carb and tranny. I am wondering if there is supposed to 2 springs for this set-up. The throttle return spring (which you can see in the picture) AND an additional spring that might attach "forward" of the throttle shaft toward the radiator? The kick down is not working properly. Meaning the secondaries are NOT opening with the gas pedal to the floor. I'm wondering if its a Physical set up issue or a lack of vacuum issue or both. The other issue is that the throttle is not returning far enough to get the idle as low as it should be. The dashpot is NOT in the way. So....???

 

[1970 Palmer]

Wow...........I'm confused!

First, that carb did not come on a "K" code 271 HP originally (or it's been modified by changing the throttle shaft to a kick down style). No "K" codes ever had C4's originally that I have seen. All were either T-10's or Top Loader four speeds. Back in the day I owned a 64 Fairlane Sports Coupe that was an original "K" code car, but it was purchased originally by a DR. and he had it converted to a C4 with all original factory parts. This was my daily driver in the late 60's. It looked 100% original except they left the clutch pedal assembly in it. So, the 4100 carb likely came from another FE motored car with an automatic that used the mechanical kick down rod. The 4100's were used until the late 60's, when we started to see most of the low performance V8 motors come with 4300 Autolites.

How do you know the secondaries do not open? Why do you suspect a vacuum problem? What does the carb's vacuum operated secondaries have to do with the transmission kick down rod? Yes, it had a very light tension spring that connected to the hole at the top of the hole just in front of your kick down rod. The dash pot (anti stall) mounting bracket had a small hole right near the carb mounting stud, as I remember. As long as the kick down rod returns, it will work fine just the way you have it. Just have someone sit in the vehicle. Push the throttle down fully to the floormat and make certain the carb linkage is adjusted to give you full throttle at the throttle plates. Then before they let up, take your thumb and see if the kick down rod is actually manually down shifting the transmission valve body. It's possible, especially when assembling a system from various parts sources, to have the kick down rod prevent the carb from reaching full "open throttle", so it's a good thing to check and takes only a minute.

IMO, it's very doubtful you actually need the accelerator fuel pump rod in the top adjustment hole. The second hole is fine and gives enough fuel shot even in cold weather.

You don't show any pictures of the right side of the carb. Is it a manual choke or automatic choke? If automatic, how is it heated? Have you installed a closed loop heat tube for the choke? You don't want the carb sucking dirt into your new engine.

You will never be able to see the vacuum secondaries open unless you could load the engine, and also get it to turn enough RPM on a dyno. If everything is adjusted correctly to stock settings, that 4100 carb is going to work great on your engine. You can play with different tension and length secondary springs, but the stock setup worked very well and never gave a problem.

I would disconnect your transmission kick down rod. Next disconnect the throttle linkage. Just leave the throttle return spring attached. Start the engine, let it fully warm up. Make certain you do not have any of the fast idle choke linkage holding the throttle open. This linkage is on the right (passenger side) of the carb. You should be able to get it to adjust to run at 700-800 RPM and have the idle mixture screws be sensative to adjustment. If the initial timing is over 10-12 degrees, it's not going to have a normal idle. You want only "ported vacuum" run to the vacuum advance distributor, not manifold vacuum.

I worked as a tune-up tech at a large volume Arizona Ford Dealership '65-'71 and have rebuilt hundreds of Autolite 2100/4100 series carbs.

John

 

[jnirenstein]

Wow...........I'm confused!

First, that carb did not come on a "K" code 271 HP originally (or it's been modified by changing the throttle shaft to a kick down style). No "K" codes ever had C4's originally that I have seen. All were either T-10's or Top Loader four speeds. Back in the day I owned a 64 Fairlane Sports Coupe that was an original "K" code car, but it was purchased originally by a DR. and he had it converted to a C4 with all original factory parts. This was my daily driver in the late 60's. It looked 100% original except they left the clutch pedal assembly in it. So, the 4100 carb likely came from another FE motored car with an automatic that used the mechanical kick down rod. The 4100's were used until the late 60's, when we started to see most of the low performance V8 motors come with 4300 Autolites.

How do you know the secondaries do not open? Why do you suspect a vacuum problem? What does the carb's vacuum operated secondaries have to do with the transmission kick down rod? Yes, it had a very light tension spring that connected to the hole at the top of the hole just in front of your kick down rod. The dash pot (anti stall) mounting bracket had a small hole right near the carb mounting stud, as I remember. As long as the kick down rod returns, it will work fine just the way you have it. Just have someone sit in the vehicle. Push the throttle down fully to the floormat and make certain the carb linkage is adjusted to give you full throttle at the throttle plates. Then before they let up, take your thumb and see if the kick down rod is actually manually down shifting the transmission valve body. It's possible, especially when assembling a system from various parts sources, to have the kick down rod prevent the carb from reaching full "open throttle", so it's a good thing to check and takes only a minute.

IMO, it's very doubtful you actually need the accelerator fuel pump rod in the top adjustment hole. The second hole is fine and gives enough fuel shot even in cold weather.

You don't show any pictures of the right side of the carb. Is it a manual choke or automatic choke? If automatic, how is it heated? Have you installed a closed loop heat tube for the choke? You don't want the carb sucking dirt into your new engine.

You will never be able to see the vacuum secondaries open unless you could load the engine, and also get it to turn enough RPM on a dyno. If everything is adjusted correctly to stock settings, that 4100 carb is going to work great on your engine. You can play with different tension and length secondary springs, but the stock setup worked very well and never gave a problem.

I would disconnect your transmission kick down rod. Next disconnect the throttle linkage. Just leave the throttle return spring attached. Start the engine, let it fully warm up. Make certain you do not have any of the fast idle choke linkage holding the throttle open. This linkage is on the right (passenger side) of the carb. You should be able to get it to adjust to run at 700-800 RPM and have the idle mixture screws be sensative to adjustment. If the initial timing is over 10-12 degrees, it's not going to have a normal idle. You want only "ported vacuum" run to the vacuum advance distributor, not manifold vacuum.

I worked as a tune-up tech at a large volume Arizona Ford Dealership '65-'71 and have rebuilt hundreds of Autolite 2100/4100 series carbs.

John

Thanks John for the AWESOME answer!! Yes now that I think about having owned a 66 K code Mustang way back when, this CARB set up would never have been on a K code car (Maybe a Shelby GT350H since they were automatics?) Anyway. I appreciate the detailed answers. I have converted this carb to a Manual choke as that's what my Bronco had and I like manual chokes. I suspected that an additional spring might be called for near the dashpot. The Carb came from the shop that rebuilt it with the accelerator pump rod in the hole seen in the pics. I WAS going to move it to a lower hole but the clip felt like it was going to break so I left it alone. I have driven the truck gently around my shop at Sonoma Raceway. We have some good hills so I noticed when pulling up the hill under load that the secondaries never "felt" like they were kicking in. And the tranny never downshifted to first when the pedal was put to the floor mid hill. So there seem to be 2 things going on:
1. The tranny doesn't downshift with pedal to the floor.
2. The throttle linkage will not return all the way to Idle unless I "help" by pushing it up against the dashpot. (there is space so not a dashpot length issue) Additional spring needed?
I'l take your advice and work through adding a spring and making adjustments as you suggest. I'll keep you posted!! Thanks again!!

 

[1970 Palmer]

Thanks John for the AWESOME answer!! Yes now that I think about having owned a 66 K code Mustang way back when, this CARB set up would never have been on a K code car (Maybe a Shelby GT350H since they were automatics?) Anyway. I appreciate the detailed answers. I have converted this carb to a Manual choke as that's what my Bronco had and I like manual chokes. I suspected that an additional spring might be called for near the dashpot. The Carb came from the shop that rebuilt it with the accelerator pump rod in the hole seen in the pics. I WAS going to move it to a lower hole but the clip felt like it was going to break so I left it alone. I have driven the truck gently around my shop at Sonoma Raceway. We have some good hills so I noticed when pulling up the hill under load that the secondaries never "felt" like they were kicking in. And the tranny never downshifted to first when the pedal was put to the floor mid hill. So there seem to be 2 things going on:
1. The tranny doesn't downshift with pedal to the floor.
2. The throttle linkage will not return all the way to Idle unless I "help" by pushing it up against the dashpot. (there is space so not a dashpot length issue) Additional spring needed?
I'l take your advice and work through adding a spring and making adjustments as you suggest. I'll keep you posted!! Thanks again!!

Disconnect all of the linkages to the carb first. Figure out why it's not returning to idle. Check the choke fast idle cam for proper operation and check the secondaries for full closure with a test light under the throttle plates. Best to remove the carb to check these things. Remove the dash pot for all of your testing. The dashpot needs to be adjusted to have 3/16' to 1/4" of drill rod clearance after you push it back manually, it should not hold the throttle open, you might need to bend the mounting bracket slightly.

Just bite off one problem at a time. Get the carb working properly before you tackle the kick down rod issue. Does it have a manifold vacuum line connected to the transmission modulator can? Make certain you have no open vacuum hoses, which will cause the same high idle symptoms.

The carb kits come with extra clips, if your rebuild shop won't give you an extra clip let me know, I'll send you some.

Looking at your photos, I don't see any air horn gasket? Is one in place?

If you can't get the transmission to down shift on a hill at full throttle (turning higher RPM), there's no reason that the vacuum secondaries should open, because it would "over carb" the engine for the load. Everything needs to work in concert.

John