Valve lapping, for or against
Discussion
Posted this on GG - was advised to post it here...
Been doing a bit of research into valve lapping in preparation for my engine head job in a couple of weeks.
Lot of forums and debate on this one - there are a lot of people some "allegedly" professional engineers etc, but like "all PH's are in the top 1% of earners and are in finance", some are suspicious...
Anyhow, the debate is generally that in modern engines, it is not advisable to bother lapping the valves, as they are usually machined with such high quality materials these days, that one could potentially cause more harm than good. There are some that say leave it well alone unless there is obviously a problem, and some that say do it anyway, every time you have the head off as it can never do any harm.
Bearing in mind that, in this case, the engine is fairly new (1999), but is a cheap piece of st...
Interesting in hearing thoughts of those who have been in precision engineering / know about it.
Been doing a bit of research into valve lapping in preparation for my engine head job in a couple of weeks.
Lot of forums and debate on this one - there are a lot of people some "allegedly" professional engineers etc, but like "all PH's are in the top 1% of earners and are in finance", some are suspicious...
Anyhow, the debate is generally that in modern engines, it is not advisable to bother lapping the valves, as they are usually machined with such high quality materials these days, that one could potentially cause more harm than good. There are some that say leave it well alone unless there is obviously a problem, and some that say do it anyway, every time you have the head off as it can never do any harm.
Bearing in mind that, in this case, the engine is fairly new (1999), but is a cheap piece of st...
Interesting in hearing thoughts of those who have been in precision engineering / know about it.
Wow an amazing amount of information so far - excellent!
They tappets are adjustable from looking at a photo of another matiz engine without the cam cover on, so I don't think they are hydraulic - I have the feeler gague at the ready as I am going to check them anyway before finishing off.
They tappets are adjustable from looking at a photo of another matiz engine without the cam cover on, so I don't think they are hydraulic - I have the feeler gague at the ready as I am going to check them anyway before finishing off.
Max_Torque said:
Assuming you have some eyes, and they work, then just look at the seat area on the valve and the valve seat, and you can tell how "knackered" the seats are. You need a nice consistent line, approx 2mm thick around the full circuference of the seat and valve. Any excessive piting is bad (leakage path, and also reduced heat transfer from valve to seat (which is the greatest cooling path for the valve).
if your seats look like this:
it's probably worth re-machining them
(if you have hydraulic tappets, you won't need to re-set valve clearances)
This is exactly the sort of answer I was looking for - very helpful! if your seats look like this:
it's probably worth re-machining them
(if you have hydraulic tappets, you won't need to re-set valve clearances)
Edited by Max_Torque on Tuesday 22 March 15:35
Will have a proper looksee when the head is off.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff