Hello all. The accelerator in my S type is quite tight, tight to the point that its quite hard to take off or change gear smoothly. I was reading a car review from about 1964 of an S type where the reviewers made the same observation. Is this the case with all S types (inwhich case I just grin and bear it) or do others have nice smooth easy and responsive accelerators (in which case I will try to fix mine)?
Cheers

 

It shouldnt be hard to move. Has it been this way or did the problem just start? Its a linkage on mine, not a cable though. Is it possible something (like a wrench or other tool) has got stuck somewhere along the twists and turns? Maybe a doorstop between the carbs (joke)?

 

Sorry, linkage. Yes its always been quite tight to depress. It moves if pushed hard enough. Trouble is that you initially push with no movement, push a little harder, then a little harder then whoosh the peddle goes down too far and instead of a nioce smooth takeoff or gear change you get jerky movements.

 

Wow. Thats just dangerous. I know its close under there, but I would start at the pedal end (personal preference) and wiggle, pry gently, push, pull, etc, all along the the linkage. You can drip penetrating fluid on the joints and the wiggling will help work it in. Seems like there has to be something in the way or maybe a bent rod causing the binding. If you dont find anything try posting a pic of the area, maybe someone can see what you dont. Good luck.

 

Yes ~ Its a linkage: It has 2 light return springs. Make sure that someone has not fitted another piggy back spring ~ It ruins the pedal pressure required. Check & lubricate the entire linkage. There are many potential binding points including badly fitted split pins. There are also wear points that might require attention. People often add a piggy back spring to achieve low idle when in fact the linkage needs attention/adjustments. Early cars had a roller on the throttle pedal. Later cars had a bell crank to improve action/feel. The linkages are a bit of a weak spot on these cars.


Linkage RHD MOD:








Springs - 75 & 76. The long one goes down to a bracket on the oil filter housing.




Early pedal with roller ~ 10:






Late Pedal with bell crank ~ 6:

 

Taking Glyn’s linkage image (one before the carb image) as an example. Bearing 27 often seizes on the cross shaft and strips clear of rubber bush 26. In turn the bush displaces from the bulkhead bracket, allowing the complete cross shaft to tilt out of alignment. This binds the bushes 14 in the rubber carrier 13. Once the bush 26 comes out of the bulkhead bracket the pedal will start to bind heavily. The whole sequence only gets worse as the cross shaft also causes mis-aligned between the pedal and roller 10.The offending bush displacement can be seen easily above the pedal position.

As the fixtures and bushes are slid into place over the inner end of the shaft it requires the complete cross shaft to be removed to replace the parts.

If parts are not available it is possible to make up the assemblies by bonding rubber bushes onto oilte type bushes and using a small ball race in place of the roller, which often wears to a flat.

Beware of losing locating key 20, this is entered (from memory) from the engine bay side. On stripping, in the engine bay you only need to undo the clamp on lever 28, withdraw it from the split collar 19, and then withdraw 19 from the shaft. This split collar may need opening a little with a screwdriver to release it from the woodruff key 20.

You would need to remove the bonnet and possibly the battery to allow access if you attempt this job.

 

As far as I can tell most of the linkage structure looks OK. I will try and lubricate what I can get to.
Are both the springs in the above images (parts 75 and 76) absolutely necessary? I see the comments that people may have fitted a piggy backed spring to increase return to low idle but what about the opposite - has anyone done away with one of those springs (eg the lighter one on the front carby)? If so how did it go. Did it make the accelerator lighter?

 

Both springs are necessary, the lighter one is to keep the butterfly valves shut on the carbs, the heavier one is to take the weight of your foot on the peddle.
There's is a stop screw adjustment on lever 83 so the carbs don't see the force of the bigger spring.

If you did away with smaller spring, then you would have to adjust the linkage to keep the butterfly valves shut and the associated shaft and it's bushing would wear prematurely.

On my car, rod 9 was binding (rubbing) on the back of the engine, so I had to put a bend in it to give it adequate clearance.

Know too that at idle the smaller spring keeps both butterfly valves shut right tight, at least on my car and what is shown here in the screen shot.
Idle and balance is achieved with the large adjusting screw on each carb just to the right where they bolted on the manifold.

That would be screw #5.
If your linkage is binding and holding both butterfly valves open at idle, it will be impossible to balance the carbs and achieve a proper idle.

 

+1 ~ both springs are critical. They are very lightweight springs.

 

As an addendum to this thread, I was under mine trying to make a good seal on the kickdown adjuster screw. I did research but could not find info on where to set the screw. I decided that I would set it at 2 turns tighter from where the screw touches its lever inside (I could feel where since the threads were quite loose). I sealed it with some thread sealer as recommended by Glyn (thanks, it seems to have worked). Later, when I started the car, the gas pedal would not move. I poked around where I had been tinkering and found that the only difference was that screw. I also could not move the kickdown linkage so that was a good clue there. I backed it back out to what I think is almost flush with the inside of the housing and tried it again. It is much better. Hope this helps someone..