I'm sorting out the throttle linkage on my dad's model A. It has what I think is probably old Speedway progressive linkage on it. The problem is when you depress the gas pedal it doesn't have enough leverage to open the outer carburetors. I thought about extending the arm on the passenger side of the carburetor to give more leverage, but I've never heard of anyone having to do this, so I started looking at the progressive linkage again. I tried hooking the throttle pedal to the extended arm on the driver's side of the carb, but it didn't give much improvement. It looks like if I moved the sliding link on the front carburetor up a hole I would have more leverage, but then it rubs the fuel line and doesn't work at all. I see Vintage Speed and Genuine Stromberg offer linkages that seem to resolve this issue, but I don't want to spend two hundred bucks on linkage that still doesn't work. Here's some shots of what I'm dealing with.
Hello, Progressive linkage is difficult to adjust for all three carburetors. But, each carb has to have the same pull and angle to open up completely. If the front arm gets moved up hole and hits the gas line, get smaller diameter gas lines or use an angle connection that goes into the carb to move the hose away from the moving linkage arm. We had to set up and adjust 6 carbs on a 671 set up for our 292 ci SBC motor. A similar fitting was used to move the gas lines away from all moving parts. Any bends in the linkage will throw out the alignment. So, other choices are necessary to get around your linkage adjustments. Jnaki Try moving up the screw attachment and see if that does work better. If it does work better, then the angle of the gas lines or smaller hoses/fittings might have to be changed first. Something like this gas line item might work for you, too. Once you get the linkage adjusted.
Hello, 1. With no linkage hooked up do the throttle shafts close completely without help? 2. If so have all three hooked together so they all open and close together. This is the easiest way. Start there and see how it runs. If you encounter trouble then we can make adjustment from there. Sent from my iPad using The H.A.M.B. mobile app
I see you have three different arms. You should have all the arms the same. By having different arms they will bind because they have different ???? I’ll call it different bolt circle. Sent from my iPad using The H.A.M.B. mobile app
How about an over head picture, looks like your throttle linkage as way to much of right angles in to pull correctly.
The first thing you need to do is get some throttle stops on the end carbs. Several ways to do this. Next, you need to center the butterfly's in the bores and check the shafts for wear and binding. Take all linkage off the left side and start from scratch with STRAIGHT linkage. You should be able to make it up with what you have. Do all of the adjusting and setup with the pump rods DISCONNECTED. After you get everything adjusted and moving freely, hook up the pump rods and be sure they all bottom at the same time. Drive the car and see if it has any flat spots or hesitations. Get the engine in good tune with right jets and plugs, THEN, if there is a throttle hesitation or flat spot, you can diddle with the progressive part of the linkage. If you get everything else right, you will get perfect throttle response with straight linkage. You will get better gas mileage also as long as you drive normal. Remember, progressive linkage is for people that can't tune an engine right.
Make sure your pump rods are all the same length. Also when you get back to the pump rods put all on summer (S). Sent from my iPad using The H.A.M.B. mobile app
It is important that all three arms are the same or close to the same angle and that angle should be close to 45 degrees but you find there is a bit of variance that you must play with to get the best result. Here is mine , forgive the crude lines I added to demonstrate the angel i am referring to. I started with the center carb to make sure it gets to WOT on it's own. Then you have an option to either pull the front carb or push the aft carb. Here I am pushing the back carb at just before half throttle, it in turn pulls the front carb with it. The arms on the rear and front must be the same length. My set up is very much like the stromberg picture you posted, mostly because it their linkage and design. I also would have had fuel line interference issues pulling the front carb, this set up works perfectly and I get all 3 carbs to WOT which is why we build them.
Thanks for the replies. I adjusted the arms so they are more parallel, and I made a new link that is curved to clear the fuel line like the Vintage Speed linkage uses. This allowed me to hook to the top hole of my front carburetor instead of the next hole down. This seems to give the extra leverage I needed to make everything work right.