@19:09 no need to discard the valve, you can trim the stem a little and get the valve height back into spec. sure you need to mark the valve that it is meant to go only in that particular cylinder from now on.
Nils, you are correct in that yes the stem can be trimmed, but only a by very small amount. Valve stems are case hardened so if you remove more than a few thousands to correct for you run the risk of going through the hardened surface. This results in in accelerated stem wear in service and will lead to an early failure. Most of the valves that we see coming out of engines today are in such bad shape in all areas of wear that new valves are always required. Thanks for watching Kurt
@@klassikats understand, your videos are very well done, it’s obvious a great deal of care has been taken to provide the level of detail required for instruction. Keep it up, thanks again and cheers mate!
Valves will tend to rotate slightly during each lift cycle so the wear will be around the entire stem and not just on one axis. The valve guide however will tend to show more wear on the thrust axis versus the side axis. Kurt
Wasn’t clear on part about installing a “new” valve. The usable length was at the max prior to cutting valve seat, i.e. it could potentially exceed the max length is how I understood that. So installing a new valve compares what? My interpretation is - In spec, non ground valve compares the material removed valve at max length before seats. Therefore new seats still leave us in usable range. To stay in a usable range, is the remaining margin, stem length and seat depth the only contributing variables? Are you recommending replacement even tho its at max range in spec b/c it guarantee a more serviceable range post rebuild with less headache? Thanks amazing video.
Using a new valve to check valve installed height is a good practice as it eliminates any grinding operations that may have been performed on a used valve. Both on the stem and on the sealing face. This allows you to determine if the valve seat is serviceable or not. There are several reason why I usually use new valves. Firstly most of the parts we are seeing today are 40 to 50 years old and often have been serviced multiple times. Rarely do i find a valve today that is still in usable specifications on all measurement positions. Secondly there is a cost factor, labor has become very expensive. sometimes even if a valve can be serviced it is just not worth it as a new set of valves will cost less than it would be to machine the old valves and it will Result in a better job.
@19:09 no need to discard the valve, you can trim the stem a little and get the valve height back into spec. sure you need to mark the valve that it is meant to go only in that particular cylinder from now on.
Nils, you are correct in that yes the stem can be trimmed, but only a by very small amount. Valve stems are case hardened so if you remove more than a few thousands to correct for you run the risk of going through the hardened surface. This results in in accelerated stem wear in service and will lead to an early failure. Most of the valves that we see coming out of engines today are in such bad shape in all areas of wear that new valves are always required.
Thanks for watching
Kurt
Discovered your training videos a few months ago. Very informative, ever do any M64 engines?
Yes, just have not done any videos on them yet.
Kurt
@@klassikats understand, your videos are very well done, it’s obvious a great deal of care has been taken to provide the level of detail required for instruction. Keep it up, thanks again and cheers mate!
Since the wear is mostly in the axis of the rocker, don't you need to measure valve stem diameter in same axis?
Valves will tend to rotate slightly during each lift cycle so the wear will be around the entire stem and not just on one axis. The valve guide however will tend to show more wear on the thrust axis versus the side axis.
Kurt
@@klassikats thank you! Good to know. I love these training videos.
your welcome
Wasn’t clear on part about installing a “new” valve. The usable length was at the max prior to cutting valve seat, i.e. it could potentially exceed the max length is how I understood that. So installing a new valve compares what?
My interpretation is - In spec, non ground valve compares the material removed valve at max length before seats. Therefore new seats still leave us in usable range.
To stay in a usable range, is the remaining margin, stem length and seat depth the only contributing variables?
Are you recommending replacement even tho its at max range in spec b/c it guarantee a more serviceable range post rebuild with less headache?
Thanks amazing video.
Using a new valve to check valve installed height is a good practice as it eliminates any grinding operations that may have been performed on a used valve. Both on the stem and on the sealing face. This allows you to determine if the valve seat is serviceable or not. There are several reason why I usually use new valves. Firstly most of the parts we are seeing today are 40 to 50 years old and often have been serviced multiple times. Rarely do i find a valve today that is still in usable specifications on all measurement positions. Secondly there is a cost factor, labor has become very expensive. sometimes even if a valve can be serviced it is just not worth it as a new set of valves will cost less than it would be to machine the old valves and it will Result in a better job.