QUESTION
I have found my camshaft moving in the bearing when I pulled on the timing chain, I removed the cam and the bearings are badly worn (800kms)
The exhaust side camshaft bearings are very rough to touch, do you know what would cause this in such a short time frame?
What is the diameter of a new camshaft journal?
C.W. - Western Australia
ANSWER
The camshaft bearing journal should measure 1.000" to 1.005" per the Lotus design specifications.
The running clearance between the camshaft and bearings should be 0.002" to 0.005".
This clearance can be checked by means of a micrometer and bore gauge or by using Plastigage.
With no valve spring, valves or cam followers installed, mechanical movement can be felt between the cam and bearings.
Having a roughened bearing shell surface suggests that contamination in the form dirty particles have been introduced in the engine oil.
It would be prudent to change the engine oil and oil filter, then remove the camshafts so they can be thoroughly cleaned.
Both camshafts should be removed from the cylinder head and placed in a solvent batch to be cleaned.
The camshafts are hollow and the end blanking plugs should be removed so a suitable bottle brush can be introduced to scrub the internal bore.
In addition to this, the cylinder head oil galley plugs should be removed and the galleries cleaned by means of a suitable bottle brush.
The forward oil gallery maybe accessed by removing the brass blanking plug adjacent to No.1 exhaust port.
On later production cylinder heads, the rear drain oil gallery maybe accessed by removing the brass blanking plug adjacent to No.4 exhaust port.
Copyright © 2014 Lotus Marques
I have found my camshaft moving in the bearing when I pulled on the timing chain, I removed the cam and the bearings are badly worn (800kms)
The exhaust side camshaft bearings are very rough to touch, do you know what would cause this in such a short time frame?
What is the diameter of a new camshaft journal?
C.W. - Western Australia
ANSWER
The camshaft bearing journal should measure 1.000" to 1.005" per the Lotus design specifications.
The running clearance between the camshaft and bearings should be 0.002" to 0.005".
This clearance can be checked by means of a micrometer and bore gauge or by using Plastigage.
With no valve spring, valves or cam followers installed, mechanical movement can be felt between the cam and bearings.
Having a roughened bearing shell surface suggests that contamination in the form dirty particles have been introduced in the engine oil.
It would be prudent to change the engine oil and oil filter, then remove the camshafts so they can be thoroughly cleaned.
Both camshafts should be removed from the cylinder head and placed in a solvent batch to be cleaned.
The camshafts are hollow and the end blanking plugs should be removed so a suitable bottle brush can be introduced to scrub the internal bore.
In addition to this, the cylinder head oil galley plugs should be removed and the galleries cleaned by means of a suitable bottle brush.
The forward oil gallery maybe accessed by removing the brass blanking plug adjacent to No.1 exhaust port.
On later production cylinder heads, the rear drain oil gallery maybe accessed by removing the brass blanking plug adjacent to No.4 exhaust port.
Copyright © 2014 Lotus Marques