Sloppy Throttle Linkage.....

[Alex_McMillin]

Ok, I'm trying to remove the slop in my throttle linkage without much success. I have TR4 with Strombergs and I can't seem to get it right. I have way too much play in the accelerator pedal before anything happens. I also can't seem to get the full range of motion at the carb from idle to full throttle. Does anyone have any suggestions and/or pictures that would help me out?

............Cheers, Alex

 

[Guest]

I don't know how the TR4 throttle linkage is arranged, but I had this same problem with my TR6 and did a few things to remedy it. First, the bushings for the pedal linkage cross shaft were all worn out. These are the nylon donuts that the pedal cross shaft travels through. A major pain to replace as they are a tight fit in the bulkhead but they are a source of a huge amount of slop in the pedal action if they are shot. Second, all those little ball and socket type joints in the linkage were loose. I pulled them all apart, cleaned and lubed everything, and then reinstalled them and adjusted the set screws to the point where they were tight but not to tight, just enough to not cause the linkage to bind. Also, under the carbs there is a point in the linkage where there is a tongue of metal that sits in a slot (don't know what this piece is called). When you press the pedal this tongue rotates up until it hits the end of the slot, then the linkage will start to move. I adjusted this so the tongue is pretty much already at the top of the slot, so when I hit the pedal there's little to no travel needed to engage the linkage on the carbs. I don't know what the purpose of having that tongue and slot arrangement is, maybe I've bypassed some saftey feature or something, but I found it completely annoying to have that much travel in the pedal and no response from the motor. After all this work my pedal action was right on, just touching the pedal lightly will give me a response. Fortunately I was pretty much already getting the full range of travel from idle to WOT, so I don't have any suggestions there.

 

[Banjo]

The pedal linkage on the firewall is made of 3 pieces.the pedal and the upright part of the rod is held to the cross shaft by a drift pin, and there is a drift pin that holds the actuator arm to the cross shaft on the other end. I bet if you have someone move the pedal back and forth, the cross shaft (from footwell to footwell) either won't move (that means the connection on the drivers side is loose) or the lever arm that actuates the linkage will have the slop. Either way see if you can get the proper drift pin to snug it up. or I've seen them tac-welded , but I woulden't reccomend that, it's not really a proper fix.

 

[jsneddon]

After dropping 2 "proper drift pins" I put a hose clamp over the holes with the pin in it. It's not pretty but it keeps the pin in place and there is no slop. I got tired of being 30 miles from home without a gas pedal... putting in a new pin on the side of the road in a place with zero hand clearance next to a blazing hot exhaust manifold was not my idea of fun.

If the 4 pedal is like the one on my 3 be sure to adjust the stop nut under the pedal so that the stop is what determines the maximum pedal travel and NOT the acutuating arm hitting the frame. That is what broke the pin the first time on mine.

 

[sammyb]

Just be glad you don't have this problem on a Porsche 911 (which I did have.) 911s are great cars, but man is the throttle linkage a rinky-dink operation! Plus, it runs under the car, and adjusting the pedal requires removing the floor board. I could never get full WOT on that stinker!

 

[Alan_Myers]

Hi Alex,

All the other suggestions are good ones. I rebuilt this linkage on my TR4 a couple years ago. It's fitted with Weber carbs, but uses a lot of the original linkage.

Here are some other things to consider.

Start at the carbs, disconnectinig all the linkage and make sure they return well, open fully with no resistance, through the full range. Dirt and/or wear inside, or weakening springs, might cause problems.

Work backwards from there, through all the linkage, to the pedal.

I added a secondary linkage return spring at the front. This hooks to a notch I filed into the crank arm on one end and forward to one of the radiator braces on the other end. You might need to arrange differently, but the idea is to eliminate all linkage slop. I plan also to add two more "safety" springs at the carbs (to a bracket on the valve cover), which is required by most racing organizations.

Next, the end fittings on my car's linkage were heavily worn. Adjustment is possible, or it might be better to replace the ends with new. Both the ball and the fitting that snaps onto it can wear. Unfortunately, many replacements are non-adjustable and simply snap together.

If using the original, adjustable type, be sure there is a cotter pin or safety wire in the end, preventing the adjusting screw from backing out, which might let the linkage drop off. There are a series of small holes around the peripehery for the cotter pin or safety wire. If not too worn, the cotter pin or safety wire will pass through the screwdriver slot, once adjustment is correct. If heavily worn, the screwdvriver slot will be too deep for the cotter pin/safety wire to hold anything.

If you aren't concerned about originality, it's possible to make up your own linkage using 1/4" rod-ends from a hardware store, or put these types of ends onto the old linkage rods. One of my local hardware stores sells rod-ends in a variety of sizes, both male and female, both righthand and lefthand threaded. They also were a good source aluminum rod or tubing, or steel if preferred. Most racing organizations require rod-end type linkage, because it's trapped, cannot come completely apart and will at least work partially in the event of a failure.

At the firewall on your car, there are those two nylon bushings on either side, as mentioned already. Those are most likely a source of a lot of slop in the linkage and are available from the major Triumph parts sources. The clamshell cups they fit in can be hard to find, though they usually don't wear and don't need replacing.

There is also a simple brace near the linkage lever - really nothing more than a sheet metal tab that's welded to the firewall - with the shaft passing through it. The metal against metal arrangement wears too and this allows the lever shaft to move sideways, adding more slop. So, I got hold of an extra nylon bushing and welded a spare set of clamshells (which normally hold it onto the firewall at either side) onto this bracket. This added a third bushing to the shaft. It reallly helped a lot!

Finally, the roll pins in the shaft do work loose and drop out. Yet, it is necessary to separate the shaft in order to remove the pedal/linkage from the car, making welding less than desirable. So I replaced all of the pins with small socket headed screws, after enlarging th holes slightly and tapping the sleeve and shaft all the way through. A little Locktite and there ain't no way those will fall out again. This also makes disassembly a lot easier back behind the head and engine, if and when that ever becomes necessary.

Hope this helps!

Alan

 

[Guest]

Alex, if you think that you need to replace the adjustable ball-and-socket linkage that goes from the actuator arm to the carb throttle lever, there are two types available. I got one from a vendor on the west coast. Clever design, piece of crap. The Roadster Factory had some manufactured that are exact replicas of OE and are of outstanding quality, and cheaper. Go figure.

Bill

 

[AltaKnight]

Hi Alex....
I know there's supposed to be some "lost motion" in the linkage for safety reasons so that the throttle can't hang partly open with disastrous results.
Having said that, I went ahad on my TR6 and adjusted out a lot of the slop to make it nicer to drive. As Scott suggests above the TR6 has 2 bushings on the xshaft through the firewall, not sure on your car if it's the same, but that was where I eliminated about 85% of the slop. Those darn bushings are sure tough to install though! /ubbthreads/images/graemlins/eek.gif

 

[Alan_Myers]

>Those darn bushings are sure tough to install though!<

Right you are!

The easiest way is to first remove the engine and gearbox...

Alan

 

[Alex_McMillin]

Thanks for all the info everyone. I was just wondering if any of you have converted over to a cable setup? If so, where did you get your parts from? I switched to a cable setup on my 68 Mustang, and it works great, nice and smooth.

...........Cheers, Alex

 

[Adrio]

I don't know if your TR4 with Strombergs has the exact same set up as my TR4A with SU but... In my case there was something called a "lost motion lever" (Moss part # 372-840)into which a pin at the end of an arm went. The pin was much smaller then the socket in the "lost motion lever". This resulted in the exact condition you describe. Given the name "lost motion" I assume this was intended. None-the-less I did not like it and so I bought a couple of bronze bushings that fit over the pin to take up the slack. It worked great. If you have the same set up I would recommend doing the same.

If anyone knows what the reason for the "lost motion lever" is I would love to hear it. Especialy so that I can decide if my "fix" will have some unforseen problem down the road.

 

[vettedog72]

Thanks Alan, that's another keeper.

 

[trrdster2000]

Alex, I have done a few TR's to cable and it's real easy. Get the pedal out of a Spitfire or GT6, now the trick is to get the measurements right on the two holes you will have to drill in the firewall. If the wreck you get the parts off has some of the carb bits get the slotted bracket off for your manifold as you will have to rig up a holding bracket for the carb end that bolts onto your manifold. The next thing is to get the hole right for the cable on the flat part of the firewall and you are in business. For anyone doing this on a TR6 or TR4 just remember that the you will have to put the cable bracket so it pulls in the right direction, on the six you will have to turn the lever on the carbs toward the manifold side to be able to pull up. On the TR6 it takes a GT6 cable but you should be able to use the Spitfire one on the TR4. The GT6 one is a bit longer, and if I was going to buy one without having an old one to try I would get the GT6 to start. Sounds easy and it really is and will you ever be happy with the results if you get it right. Wayne

 

[vettedog72]

trrdster2000:
I sure wood like to see some pictures of the set up you described, especially of the TR6 set up. I don't know any of the the other Triumphs, just the TR6. Can you post any pictures?

 

[Alan_Myers]

Hi,

I recently photographed the throttle linkage modifications on my TR4 and am attaching a picture, FYI.

This is a photo of the extra bushing installed in place of the plain bracket that's normally used and giving the throttle shaft a total of three nylon bushings supporting it. The original plain bracket was worn badly and allowed a lot of slop, leading me to believe some extra support would be helpful.

The bushing is the same nylon self-centering ball used at either end of the throttle shaft, and the "keepers" it fits in are extra originals I tracked down. One of these was welded to the original bracket, the other bolts on. As you can see, a sleeve with a shoulder was also fitted to the shaft and sized to fit inside the nylon bushing (turned on my homemade metalworking "lathe"... which is nothing more than a half inch drill and a large file).

The only other modification was to replace the roll pins and split pins throughout with small bolts, #4 or #6, if I recall correctly. The holes were tapped to accept these and some of the key ones have locking nuts on the opposite side.

No slop in this throttle linkage now! All the other parts are being renewed and repaired as needed, forward to the twin Weber DCOEs. On most of it, I'm using rod ends instead of the original ball fasteners. Rod ends are a little more hassle to remove or install, but are relatively "failsafe".

A cable is certainly another possibility. I see in a recently acquired TR6 shop manual that some (at least the RHD model shown) used a cable arrangement.

Cheers!

Alan Myers
San Jose, Calif.
'62 TR4 CT17602L

 

[trrdster2000]

vettedog72, Sorry about the pictures, as I have been doing this stuff for forty years and it's been about ten since I did one and the linkage on my TR6 is all good, so I won't be doing it for a while. The Spitfire has a bolt on gas pedal and if you can just find someone with one and get a look at it you will see how simple it is. Wayne

 

[vettedog72]

OK, you will get a laugh at this one: I thought the slop in the throttle linkage was to allow for the chassie/body flex. That's why the cable idea sounds so good to me. I guess there is not much flex in the fire wall, but the shuttle does shakes a bit.

 

[Alex_McMillin]

Thanks for all the help. I had previously converted my 68 Mustang over to a throttle linkage setup, and it is fantastic. I was all set to do the same on the TR4, but ended up breaking down the entire linkage and found that the hole the roll pin, on the passenger side, goes in was very oval. That created A LOT of slop. I cleaned it up and redrilled another hole inserted a new roll pin and VOILA! No more slop and was able to get full accelerator motion.

Thanks again for all the input.

............Cheers, Alex

 

[AltaKnight]

Perfect, you just added 20MPH to your top speed! /ubbthreads/images/graemlins/devilgrin.gif