Leaking valves or leaking seats - or both?

John Reynolds

Well Known and Active Forum User
VOC Member
I have had my heads professionally overhauled but have now discovered that there are leaks from the combustion chambers into the ports - all of them! I have confirmed this by the old trick of filling the inverted combustion chamber with petrol and checking for leakage into the ports. However, the overhaul involved fitting both new valve seats and new valves, so the leakage could be through the valve/seat interface or through the seat/head interface - or both. Can anyone suggest a test which will determine at which interface the leakage is occurring?
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
I have had my heads professionally overhauled but have now discovered that there are leaks from the combustion chambers into the ports - all of them! I have confirmed this by the old trick of filling the inverted combustion chamber with petrol and checking for leakage into the ports. However, the overhaul involved fitting both new valve seats and new valves, so the leakage could be through the valve/seat interface or through the seat/head interface - or both. Can anyone suggest a test which will determine at which interface the leakage is occurring?
Why not just go back to the professional who did the job??
 

davidd

Well Known and Active Forum User
VOC Member
Yes, lap them by hand with some grinding paste and it will show on the valves and seats. If they were previously lapped, you might need to use some Prussian Blue to see the contrast, but it sounds like it should show the gaps well. If you can lap them well, then the test becomes the cure.

David
 
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