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The journey begins. Already found a couple of little things I need to investigate.
First the idle speed. Car starts well and the automatic choke functions OK. I do have an override switch but I have not needed to use it.
After a longish drive where the engine performed beautifully I stopped for petrol and noticed the engine was idling at a little over 1000 rpm.
Filled up with petrol and started again and now the idle was around 500 rpm. What would cause the idle not to drop? I tried blipping the throttle but it still just came down to 1000.
When I stopped the car a couple of times I have noticed a little dieseling, not sure if this is related.
a dirty throttle linkage can play havoc in attaining a consistent return to idle and IME the most likely and, fortunately, the easiest to fix. the next most likely culprit would be a worn out throttle shaft and/or the bushings in the carb bodies. not so easy, and much more expensive to fix. could even be in the accelerator-pedal-to-throttle-shaft connection. i've had success, albeit probably short-term, on occasion by simply lubricating the moving parts associated with the accelerator, from cabin to carb, and driving it for a while.
The 2 throttle return springs are very light on these cars & might need replacement. Does the car have a CR of 9 to 1 with 9 to 1 pistons & a slight head shave? What Octane of fuel did you use? If Idle is high and Octane is borderline you can suffer run on. You have got to get the idle to settle below 1000RPM. Max 700RPM. That Wiki article on "dieseling is pathetic".
Last edited by Glyn M Ruck; Mar 14, 2024 at 09:18 PM.
Worn throttle shafts as mentioned will cause dieseling because if they cause the butterfly valves not to fully shut after switching off the ignition, fuel and air will continue to enter the engine.
This will cause dieseling.
Too rich a mixture as well _ what do your plugs look like after a long drive ?
It would be extremely difficult to muddle the throttle springs. They vary considerably in length. Short top location, long bottom to oil filter housing bracket. Getting these cars to settle to proper idle requires every point of the linkage to be nice & free. My 8 to 1 CR engine will run on if it does not settle to correct idle speed. I won't use the language used by a colleague, criticising the linkage on the Register.
On no account use stronger springs. You will increase carb wear.
Last edited by Glyn M Ruck; Mar 14, 2024 at 08:47 PM.
Idle speed
