QUESTION
Several Lotus Esprit turbo owners have confirmed that there is a discrepancy between crank "0" deg mark on the front crankshaft pulley and fly-wheel TDC mark on some 1986-88 US Federal cars.
Can you please offer an explanation and which mark is correct?
C.G. - USA
ANSWER
There is a previous article in the knowledge-base which explains this manufacturing error and checking method.
The fundamental question to this problems is - which timing mark is correct, the front crankshaft pulley or flywheel?
To begin with you have to assume both are incorrect.
To determine which timing mark is correct, the initial task is to check and determine the true TDC piston position.
There are two ways of doing this and installing a mechanical stop (modified spark-plug and protruding bolt thread) is the easier.
A spark-plug can be suitably modified by first removing the insulator material and electrode.
Next step is to drill and tap the plug body to accept a convenient bolt size of 3/8"UNC x 3" (75mm) long.
The fully threaded bolt can then be screwed in from the top of the plug to allow 3/4" (19mm) of thread to protrude from the nose.
The plug can then be gently screwed into No.1 spark-plug hole, the engine carefully turned clockwise and anti-clockwise whilst noting the points where the crank stops turning.
The mid-point between the two mechanical stop points is true Top Dead Centre (TDC).
This procedure should be repeated on both the crankshaft pulley and flywheel to determine which set of markings are correct.
Its also wise to check the camshaft timing after determining the true TDC timing mark.
If the cylinder head has ever been skimmed whilst being serviced, it will retard the cam timing (on both cams and the engine will have a reduced power output)
Adjusting the cam timing to the correct MOP (Maximum Opening Point) is the cheapest horse-power you will ever realise from an engine.
Copyright © 2012 Lotus Marques
Several Lotus Esprit turbo owners have confirmed that there is a discrepancy between crank "0" deg mark on the front crankshaft pulley and fly-wheel TDC mark on some 1986-88 US Federal cars.
Can you please offer an explanation and which mark is correct?
C.G. - USA
ANSWER
There is a previous article in the knowledge-base which explains this manufacturing error and checking method.
The fundamental question to this problems is - which timing mark is correct, the front crankshaft pulley or flywheel?
To begin with you have to assume both are incorrect.
To determine which timing mark is correct, the initial task is to check and determine the true TDC piston position.
There are two ways of doing this and installing a mechanical stop (modified spark-plug and protruding bolt thread) is the easier.
A spark-plug can be suitably modified by first removing the insulator material and electrode.
Next step is to drill and tap the plug body to accept a convenient bolt size of 3/8"UNC x 3" (75mm) long.
The fully threaded bolt can then be screwed in from the top of the plug to allow 3/4" (19mm) of thread to protrude from the nose.
The plug can then be gently screwed into No.1 spark-plug hole, the engine carefully turned clockwise and anti-clockwise whilst noting the points where the crank stops turning.
The mid-point between the two mechanical stop points is true Top Dead Centre (TDC).
This procedure should be repeated on both the crankshaft pulley and flywheel to determine which set of markings are correct.
Its also wise to check the camshaft timing after determining the true TDC timing mark.
If the cylinder head has ever been skimmed whilst being serviced, it will retard the cam timing (on both cams and the engine will have a reduced power output)
Adjusting the cam timing to the correct MOP (Maximum Opening Point) is the cheapest horse-power you will ever realise from an engine.
Copyright © 2012 Lotus Marques
