I have a question, on my old CB900 the book says this is a bad idea and will cause instant valve failure as the valves and seats have a special coating that is destroyed by lapping, though I can't find much info on the web about this, anyone got comments?
my car was running fine.. Project rebuild.(video of same day in my videos) I forgot to add anti freeze and my water pump freezed alittle and caused my cambelt to slips. I gently hit all 8 exhuast valves leave e shiny marks at the bottom of all the valves. My compression test showed 75-70-65-68. I removed the head and removed all the valves but they seat perfect without the cam installed. when cams fitted they stay open sightly but none of the valves look bent. i have no idea what todo.
@antonyr123 You need to check the run out on the valves. Put a dial indicator on the valve without the spring installed and turn it. You can also use Dyechem on the valve where it contacts the seat and turn it. The blue will still be visible where it's not making contact. Waterpump on an RB shouldn't have anything to do with the cam belt, so you may want to look for the root-cause someplace else.
@MJRPerformance this is only my 2nd head rebuild. Because its my track car i may just replace everything. just over £250 for all parts inc headgasket,inlet and exuast
I still don't think none english speaking lads will get it. The first demo was funny. Oval heaven. The second, showed a few mistakes. Noone is perfect. Rushed valve grinding well highlighted.
The ports looked nices
Nice vid, needs some text overlay and pause to be topps!
Nice to see someone try to explain proper lapping for a change.
Too many people use the drill nowadays, or just don't bother.
Engineers blue should be used to show good and bad grinding! pls put one on with blued seats
Two more things I have wondered about: Are the valve guides still in the head when you do this and are each individual valve have to go back exactly in the same position they were in before you started your work? Thanks and great video. RH DSD
Valve guides are in. I use dyechem blue to check the pattern. Like I said before, if it takes more than a few minutes of grinding per valve, they get cut.
@MJRPerformance I'm rebuilding My 2.8 24V VR6 head. I'v done alittle grinding before but never had a perfect head. how much time do u spend on each valvle while at the speed in ur video.
@antonyr123 My rule of thumb is about three minutes per valve at the outside, in one minute increments. If you do this and can still see pits or bad contact area, the valve and seat should probably be cut
@DIOSpeedDemon At the end of the video you can see the gray-concentric line where the contact area is. It should look the same all the way around and the valve should look the same. Any pits should be gone. This is for a rebuild where the valves are in good condition. My rule of thumb is about three minutes per valve at the outside, in one minute increments. If you do this and can still see pits or bad contact area, the valve and seat should probably be cut.
@DIOSpeedDemon Other way to check if you do it right: (with the valve & springs installed) whith the head stand up, fill the intake port with fuel or kerosene and then wait 15/20 minutes to verify a possible leaking fuel from the combustion chamber side. No leaks it's OK (my english sucks!! sorry)
What works best for me is to use a variable speed reversible drill. I tape the valve to protect it from marring and oil the guide real good. This method has worked well for me for many years.
My suction cup broke off my stick. I still managed to get it done right using my fingers but it took forever. No I have lappers cramp. Very good, I used to do it the second way but I will try to pop it next time.
I have a question, on my old CB900 the book says this is a bad idea and will cause instant valve failure as the valves and seats have a special coating that is destroyed by lapping, though I can't find much info on the web about this, anyone got comments?
voicefreson 11 months ago
where can u buy the compound for valve lapping its kinda look like a grease though w small sand in it?
andrewmylyf 11 months ago
do you need to remove the valve keepers, springs and all for this job? thank you!!
virginia1882 1 year ago
my car was running fine.. Project rebuild.(video of same day in my videos) I forgot to add anti freeze and my water pump freezed alittle and caused my cambelt to slips. I gently hit all 8 exhuast valves leave e shiny marks at the bottom of all the valves. My compression test showed 75-70-65-68. I removed the head and removed all the valves but they seat perfect without the cam installed. when cams fitted they stay open sightly but none of the valves look bent. i have no idea what todo.
antonyr123 1 year ago
@antonyr123 You need to check the run out on the valves. Put a dial indicator on the valve without the spring installed and turn it. You can also use Dyechem on the valve where it contacts the seat and turn it. The blue will still be visible where it's not making contact. Waterpump on an RB shouldn't have anything to do with the cam belt, so you may want to look for the root-cause someplace else.
Good luck.
MJRPerformance 1 year ago
@MJRPerformance this is only my 2nd head rebuild. Because its my track car i may just replace everything. just over £250 for all parts inc headgasket,inlet and exuast
I'll post a video up later on today if i get time
antonyr123 1 year ago
what does this do performance wise?
evilrider187 1 year ago
@evilrider187 Refreshes the seal between the valve and seat. Over time tiny pits occur due to erosion.
MJRPerformance 1 year ago
I still don't think none english speaking lads will get it. The first demo was funny. Oval heaven. The second, showed a few mistakes. Noone is perfect. Rushed valve grinding well highlighted.
The ports looked nices
Nice vid, needs some text overlay and pause to be topps!
Nice to see someone try to explain proper lapping for a change.
Too many people use the drill nowadays, or just don't bother.
Engineers blue should be used to show good and bad grinding! pls put one on with blued seats
bigstiggerNo1 1 year ago
Two more things I have wondered about: Are the valve guides still in the head when you do this and are each individual valve have to go back exactly in the same position they were in before you started your work? Thanks and great video. RH DSD
DIOSpeedDemon 1 year ago
@DIOSpeedDemon
Valve guides are in. I use dyechem blue to check the pattern. Like I said before, if it takes more than a few minutes of grinding per valve, they get cut.
MJRPerformance 1 year ago
@MJRPerformance I'm rebuilding My 2.8 24V VR6 head. I'v done alittle grinding before but never had a perfect head. how much time do u spend on each valvle while at the speed in ur video.
antonyr123 1 year ago
@antonyr123 My rule of thumb is about three minutes per valve at the outside, in one minute increments. If you do this and can still see pits or bad contact area, the valve and seat should probably be cut
MJRPerformance 1 year ago
Excellent video, HOw do you know when the process is complete and done right with no mistakes, thanks, 5 stars.
DIOSpeedDemon 1 year ago
@DIOSpeedDemon At the end of the video you can see the gray-concentric line where the contact area is. It should look the same all the way around and the valve should look the same. Any pits should be gone. This is for a rebuild where the valves are in good condition. My rule of thumb is about three minutes per valve at the outside, in one minute increments. If you do this and can still see pits or bad contact area, the valve and seat should probably be cut.
MJRPerformance 1 year ago
@DIOSpeedDemon Other way to check if you do it right: (with the valve & springs installed) whith the head stand up, fill the intake port with fuel or kerosene and then wait 15/20 minutes to verify a possible leaking fuel from the combustion chamber side. No leaks it's OK (my english sucks!! sorry)
soybiensudaka 1 year ago
What works best for me is to use a variable speed reversible drill. I tape the valve to protect it from marring and oil the guide real good. This method has worked well for me for many years.
Thefactsasiseethem 1 year ago
My suction cup broke off my stick. I still managed to get it done right using my fingers but it took forever. No I have lappers cramp. Very good, I used to do it the second way but I will try to pop it next time.
admiralboner 2 years ago
when i was an apprentice i had to do this on a 32 valve v8. takes ages to do it properly
bunchofdicks 2 years ago
@bunchofdicks
and thats the exact reason i do all my own engine work.
bet the guy with the V8 would be totally pissed off if they knew some spotty little apprentice had been at his valves.
CharliesDaddy22 1 year ago
@CharliesDaddy22 Any need for the insult? Thought I was very competant for an apprentice, now a master tech.
bunchofdicks 1 year ago
Thanks for the awesome rebuild videos! I hope to see more of them soon! (If you ever decide to do RB25 rebuild video's that's be awesome too!)
Mikecom32 2 years ago