suspect fuel supply on an SC

[hot66]

Have you,tried running it without the gas tank cap ?

[Peter Roberts]

Eureka!!!!!! My serious misfire has gone at last. After a year of restoration having a misfiring engine did not please me.
After 8 weeks of struggling, cursing and racking my brains i , with the help of a friend, have found the problem.
During this period i have changed the ignition leads, distributor cap and plugs. I checked the timing, stripped the carbs and blown through all the jets whilst checking for leaks on the inlet manifold. I also checked the fuel level in the float chamber. A compression test showed all cylinders up to scratch at 9 bar plus.
It would start on the button but would not rev properly and was misfiring. Tickover was ok but not correct.
I could not find a reason for the misfire and spitting and had no reaction from the idle jets when adjusting them.
With the help of a knowledgeable friend to put a fresh pair of eyes on the job we started from scratch. We discovered that it was not firing on cylinders 3 and 4 when i had imagined it was cylinder 1 because that was spitting and backfiring.
As it was now 2 cylinders we stripped off the carb top again. Fuel level perfect, jets clear. Now he was feeling as i have felt for the last 2 months.
As a last resort he suggested checking the needle valve on the float. I had not done this as i had rebuilt the carbs and put in new needle valves so what could be wrong with that when the fuel level in the carbs was correct. WE turned the engine over with the carb top off and the flow was negligible.
On stripping the needle valve i discovered two tiny pieces of rubber in the valve. They looked too big to have come down the fuel line and through the valve body but however they got there they were there.
A quick rebuild and at last the problem was solved and i have 4 cylinders popping again.
I can only surmise that the fuel supply was very restricted but enough to get the engine running and ticking over but on reving the fuel level in the carb was dropping and the cylinders cutting out. When i stopped the engine the residual pressure in the line slowly filled it back up so by the time i had removed the top off the carb the fuel level was correct.
At last i now will be able to enjoy my labour of love over the last 12 months restoring this beauty and will probably soon forget the last 2 months. At my advanced age forgetting comes naturally.
Will post some pictures soon as the car has turned out really well.