I decided to make a little upgrade to the car to help with a very minor issue that I decided to rectify. The modification also added a little blink under the hood and something else to clean while I’m at it.
The issue was that on the odd occasion when lifting my foot of the throttle and stopping the idle would be a little too high. This could be cured by tapping the gas pedal and it would settle down again. On investigation it appeared to be the throttle return springs on the standard throttle rod didn’t strong enough to return the carb throttle body to it’s correct closed position every single time.
For a stock set up there is a single spring to return the angled throttle rod. Not very safe if the spring breaks or stretches as it could leave an open throttle. So the simple fix is to fit a secondary larger spring around the outside of the smaller spring. Although this configuration was fine the throttle feel was very light under foot.
I spoke to Adam who advised a rose joint billet throttle rod would help with the feel, but an alternative spring return would be needed if you swapped the rods out, more on that in bit. So I came home with a new throttle rod. I wasn’t to keen on the billet satin finish, so I spent a few hours sanding and polishing down to a shiny version which came out really well.
The first job was remove the old rod from the carb throttle body which was held in place by a lock nut. The two springs on the dog leg part of the old rod simply unhooked.
The second task was to remove the other end from the gas pedal bushing which is held in place by a split pin.
With the old rod removed I could compare the length of the original stup to the new rod which was also adjustable. The first pic shows the shine I managed to get on the billet rod.
These billet rods have a left hand thread and a right hand thread, so when twisting the rod in the middle it winds out both ends in or out for a synchronous adjustment. I set the rod to be the same length by default as the old one for now. The gas pedal needed to be a little higher inside the car for my liking as well, again more on that a little later.
I unscrewed the carb end of the new rod which has a conical fixing to fit inside the larger carb throttle body nearer the top for a test fitting and to see how the rose joint fitting would locate. The fitting was bit loose and required a single washer to pack out the gap in order to pull the rose joint firmly into the throttle body without any lateral movement. The movement now all comes from the rose joint itself.
(Note the old satin finish here.)
We now leave the throttle rod fitting at this point as the new return springs had to be fitted next. This would also make life easier with everything out of the way.
The return springs are Holley kit upgrades with an additional bracket, a spring levelling ring body fitting bolts and a choice of springs.
The original return spring is on the left. Although it’s shorter and slightly fatter, it had less distance to cover. The other springs have a much bigger gap to span and they have a different stronger positive tension when stretched. You will also notice the double loop closed ring ends on the Holley springs where they simply can’t become detached from the brackets.
Depending on the combination of springs, it will determine the overall feel of the throttle. I decided that the stronger pair for a max return would be my choice. There are two holes on the carb fitting ring (left picture), and two on the bracket. I made the mistake of putting the springs on the ring first.
This made life very difficult while trying to attach the pair of springs to the bracket as there wasn’t enough movement to allow the second spring to attach without tangling the other spring. So I had to remove one of the springs in order fit to the bracket first then onto the throttle ring. The secret is to fit first spring to the ring as you normally would, then the second spring fitting needs to be twisted in reverse first to allow the open ring to untwist and end up where it should be. If you don’t the springs will tangle and be twisted once fully fitted. I won’t deny it, it took me a few attempts to get right, the air did turn the same colour as the car, very blue as the springs tangled up on the first couple of attempts.
Eventually I manged to connect both sections.
To fit the bracket it needs to locate over a corner stud with the bigger hole that holds the carb in place. If the stud was longer then a second nut would bolt the bracket down.
A second smaller bolt nearer to the front of the bracket that also holds the spring bracket in place and to stop the bracket twisting when the springs are under stress.
As I have a 1″ phonetic spacer the bolt that bolts the carb down sits at the top end of the stud. That means I couldn’t bolt it down without changing out the stud. However, the top of the stud was protruding enough to act as a locating pin to stop any twisting.
To make sure the single bolt holes the bracket in place I fitted a large washer. The down side was that the washer was overhanging the bracket and snagging on the throttle body. This meant that I had to grind two edges flat to align with the carb body and then finish at the bracket’s edge. You can just about see odd shape in this picture. A smaller washer would have been fine I just wanted max hold.
With the bracket held firmly in place the tricky task of fitting the spring ring to the carb throttle body. In an ideal situation you could do with a third hand to do it easily. You need to thread the screw through the rose joint, washer and the conical spring ring in that order.
With the cone in place and the ring under tension to the bracket, you need a larger washer to stop the spring ring coming of the end. I didn’t use provided lock nut, but I still wanted to lock the bolts in place. Nut number one labelled holds it all together, number two locks the two together.
From the pic above you will see that I found it easier to have the rod unscrewed to fit it all together. Below pics are from the back and front views.
Now I could thread the rod back onto the rose joint.
The other end was a simple case of push the bolt through the gas pedal bushing using the supplied washer and locking nut to hold in place.
Now all was connected up I could test the range of the movement and nothing was snagging. Of course I was now pumping fuel into the carb which probably wouldn’t start as it would be flooded.
I sat in the car to check the height of the pedal I wanted. I was quite low so it needed to be adjusted. This is a simple case of turning the rod which would pull the gas pedal towards the carb for a higher pedal, or towards the firewall for a lower pedal.
Hold the rod in place with a spanner on the flats and tighten the nuts to hold the set distance in place pointed with the arrow.
Last job was to grease the moving metal to metal parts and replace the air filter.
That’s it job done.
The test drive after was good and the throttle was much snappier and returned much quicker to idle. The result I was looking for, it remains to be seen if the strong springs are to much or not. But for now, they feel fine under my size twelve feet.
6 thoughts on “Spring Doubles Up”
You certainly have an eye for detail!!
Thanks, but I am trying not to find things to do now. I need a car show like the rest of us classic car owners.
Mart, you should be a writer mate!!!! GREAT photos and description so even I could understand, well done that man!!!!
Thanks Simon, much appreciated. 👍👍
Mart, nice write-up, great photos as always!
Thank you Richard. 👍