QUESTION.
Our workshop has just rebuilt a 1985 Lotus Turbo Esprit engine and set the camshaft timing.
The engine was started so the Dellorto carburettors could be tuned.
The engine started to idle poorly soon after it was started so the engine was quickly shut down.
After running some basic checks the cam timing was found to have skipped teeth on the timing pulleys.
The cam belt tension has been checked and the semi-automatic tensioner screw has about 10mm of thread exposed.
Can you offer some suggestions what should be done to rectify this problem?
C.J. - Brisbane, Australia
ANSWER.
It would appear the timing belt tensioner mechanism has not been adjusted correctly.
But before you make any adjustments you will need to re-set the camshaft timing and check you have not bent any valves.
Whilst adjusting the camshaft timing, you may need to re-check the ignition timing as this may have been altered during this process.
Once the cam and ignition timing are correct, then adjust the threaded section of the tensioner so approximately 3mm of thread (thickness of the thin lock nut) is exposed beyond the lock-nut.
At this point, the crankshaft should be rotated 720 degrees (two complete revolutions) to ensure the applied tension has been distributed evenly around the timing belt and pulleys.
A Burroughs gauge should be used to check the belt tension ( 95lbs deflection) because with the passage of time, the dual tensioner springs become fatigued and reduce pressure.
Copyright © 2011 Lotus Marques
Our workshop has just rebuilt a 1985 Lotus Turbo Esprit engine and set the camshaft timing.
The engine was started so the Dellorto carburettors could be tuned.
The engine started to idle poorly soon after it was started so the engine was quickly shut down.
After running some basic checks the cam timing was found to have skipped teeth on the timing pulleys.
The cam belt tension has been checked and the semi-automatic tensioner screw has about 10mm of thread exposed.
Can you offer some suggestions what should be done to rectify this problem?
C.J. - Brisbane, Australia
ANSWER.
It would appear the timing belt tensioner mechanism has not been adjusted correctly.
But before you make any adjustments you will need to re-set the camshaft timing and check you have not bent any valves.
Whilst adjusting the camshaft timing, you may need to re-check the ignition timing as this may have been altered during this process.
Once the cam and ignition timing are correct, then adjust the threaded section of the tensioner so approximately 3mm of thread (thickness of the thin lock nut) is exposed beyond the lock-nut.
At this point, the crankshaft should be rotated 720 degrees (two complete revolutions) to ensure the applied tension has been distributed evenly around the timing belt and pulleys.
A Burroughs gauge should be used to check the belt tension ( 95lbs deflection) because with the passage of time, the dual tensioner springs become fatigued and reduce pressure.
Copyright © 2011 Lotus Marques
