QUESTION.
In your article about rebuilding a Lotus Esprit turbo HC cylinder head, you mentioned about the valves been measured to within 0.002" does that mean the followers are one size only?
J.G. - Perth, Western Australia
ANSWER.
You are correct with your assumption, the cam followers are usually all one size (thickness) in a the same engine.
The 0.002" dimension referred to in the article, is the tappet clearance (gap) or variation across all the relevant valves.
This is reflected in the thickness variation of 8 shims when adjusting the tappet clearance.
In other words, it is an accuracy and quality check of the valve seats and valve faces after being machined.
If care is not taken when this machining is carried out (and the correct equipment needs to be used such as a SERDI) then the all valve tip heights would be different.
Subsequently, the valve heads would be at different heights in the combustion chamber and the relevant combustion chamber volumes would all be different.
Ultimately this would change the compression ratios across all four cylinders.
Ideally all four cylinders should have identical compression ratios for the engine to run really smooth.
Lotus Marques carries a comprehensive range of high quality cam followers with different thickness friction face pads.
Followers are not usually changed or substituted when adjusting tappet clearance.
When adjusting tappet clearances, a standard range of tappet shims are used and a comprehensive shim table may be found here.
We carry a significant number of shims in stock because of the engines rebuilt in house plus the constant demand from our valued customers.
To make tappet adjustment economical, Lotus Marques offers a shim exchange service.
Copyright © 2011 Lotus Marques
In your article about rebuilding a Lotus Esprit turbo HC cylinder head, you mentioned about the valves been measured to within 0.002" does that mean the followers are one size only?
J.G. - Perth, Western Australia
ANSWER.
You are correct with your assumption, the cam followers are usually all one size (thickness) in a the same engine.
The 0.002" dimension referred to in the article, is the tappet clearance (gap) or variation across all the relevant valves.
This is reflected in the thickness variation of 8 shims when adjusting the tappet clearance.
In other words, it is an accuracy and quality check of the valve seats and valve faces after being machined.
If care is not taken when this machining is carried out (and the correct equipment needs to be used such as a SERDI) then the all valve tip heights would be different.
Subsequently, the valve heads would be at different heights in the combustion chamber and the relevant combustion chamber volumes would all be different.
Ultimately this would change the compression ratios across all four cylinders.
Ideally all four cylinders should have identical compression ratios for the engine to run really smooth.
Lotus Marques carries a comprehensive range of high quality cam followers with different thickness friction face pads.
Followers are not usually changed or substituted when adjusting tappet clearance.
When adjusting tappet clearances, a standard range of tappet shims are used and a comprehensive shim table may be found here.
We carry a significant number of shims in stock because of the engines rebuilt in house plus the constant demand from our valued customers.
To make tappet adjustment economical, Lotus Marques offers a shim exchange service.
Copyright © 2011 Lotus Marques