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Jan 19, 2011 9:30 am
Jan 19, 2011 9:30 am
Subject: Re: V12 torque loss
I would remove the air cleaner to see if the SU carburettor pistons are moving freely. You can test moving the piston up with your finger (engine not running) and it should go back smoothly without sticking. I had a piston sticking sometimes. Then I loosened the 2 screws slightly which are holding the bell, positioned the bell so that the pistons move freely and fixed the screws again. Check again after fixing. The suction chamber (bell) mounting is very delicate, if it has been moved by the polisher the pistons may stick.
The other potential problem is if a piston has a bit to much play it needs good oiling otherwise the suction when opening the throttle is not enough to pull it up (air leak). I have this on one of my carbs. As yours was fine before I think it is more likely the sticking described above.
Another thing to do might be cleaning the fuel filter. In my car it is the original one with a big number of metal plates creating the small channels for the filtration. It was full of debris.
Ignition timing has not changed ?
I would remove the air cleaner to see if the SU carburettor pistons are moving freely. You can test moving the piston up with your finger (engine not running) and it should go back smoothly without sticking. I had a piston sticking sometimes. Then I loosened the 2 screws slightly which are holding the bell, positioned the bell so that the pistons move freely and fixed the screws again. Check again after fixing. The suction chamber (bell) mounting is very delicate, if it has been moved by the polisher the pistons may stick.
The other potential problem is if a piston has a bit to much play it needs good oiling otherwise the suction when opening the throttle is not enough to pull it up (air leak). I have this on one of my carbs. As yours was fine before I think it is more likely the sticking described above.
Another thing to do might be cleaning the fuel filter. In my car it is the original one with a big number of metal plates creating the small channels for the filtration. It was full of debris.
Ignition timing has not changed ?