QUESTION
I recently purchased a set of inlet and exhaust bronze valve guides from Lotus Marques and the enclosed specification sheets says the following-
Inlet valve guide weight = 26 grams
Exhaust valve guide weight = 25 grams
However the technical specifications in the Lotus Europa Twin Cam Workshop manual on page 4 seems to say that the exhaust valve is longer which I imagine would make it heavier.
Valve guides: Length
- Inlet 36.608 mm. (1.520 in.)
- Exhaust 37.592 mm. (1.480 in.)
Is this because the material is different?
Can you please confirm that the longer/lighter ones from you are for exhaust?
G.J. - Sydney, Australia
ANSWER
I can confirm the following-
1) Inlet valve guide which is longer (1.520 inches) weighs 26 grams
2) Exhaust valve which is shorter (1.480 inches) weighs 25 grams
If you revisit the Europa TC workshop manual, page 4 you will discover there is a "classic Lotus Oops moment"
If you multiply 1.520" by 25.4 then the measurement is in fact 38.6mm and not 36.6mm as stated
Therefore 1.520" or 38.6mm is the correct length for the inlet valve guide
It is really important not to mix up the valve guides and also set the correct valve stem to guide clearance
As the valve guides do not have a stem seal, clearance accuracy should be achieved using a diamond hone
WARNING - failure to observe the correct tolerances will result in excessive oil consumption, sparkplug fouling and a smokey exhaust
This operation is critical as it influences the next cylinder head service interval
Copyright © 2021 Lotus Marques
I recently purchased a set of inlet and exhaust bronze valve guides from Lotus Marques and the enclosed specification sheets says the following-
Inlet valve guide weight = 26 grams
Exhaust valve guide weight = 25 grams
However the technical specifications in the Lotus Europa Twin Cam Workshop manual on page 4 seems to say that the exhaust valve is longer which I imagine would make it heavier.
Valve guides: Length
- Inlet 36.608 mm. (1.520 in.)
- Exhaust 37.592 mm. (1.480 in.)
Is this because the material is different?
Can you please confirm that the longer/lighter ones from you are for exhaust?
G.J. - Sydney, Australia
ANSWER
I can confirm the following-
1) Inlet valve guide which is longer (1.520 inches) weighs 26 grams
2) Exhaust valve which is shorter (1.480 inches) weighs 25 grams
If you revisit the Europa TC workshop manual, page 4 you will discover there is a "classic Lotus Oops moment"
If you multiply 1.520" by 25.4 then the measurement is in fact 38.6mm and not 36.6mm as stated
Therefore 1.520" or 38.6mm is the correct length for the inlet valve guide
It is really important not to mix up the valve guides and also set the correct valve stem to guide clearance
As the valve guides do not have a stem seal, clearance accuracy should be achieved using a diamond hone
WARNING - failure to observe the correct tolerances will result in excessive oil consumption, sparkplug fouling and a smokey exhaust
This operation is critical as it influences the next cylinder head service interval
Copyright © 2021 Lotus Marques
