Valve Lapping

Hand lapping valves on an RB26DETT head

Category:

Autos & Vehicles

Tags:

• valve
• lapping
• grinding
• rb26dett
• porting
• rebuilding

[antonyr123]

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.

[MJRPerformance]

@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.

[evilrider187]

what does this do performance wise?

[MJRPerformance]

@evilrider187 Refreshes the seal between the valve and seat. Over time tiny pits occur due to erosion.

[voicefreson]

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?

[andrewmylyf]

where can u buy the compound for valve lapping its kinda look like a grease though w small sand in it?

[bunchofdicks]

@CharliesDaddy22 Any need for the insult? Thought I was very competant for an apprentice, now a master tech.

[CharliesDaddy22]

@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.

[virginia1882]

do you need to remove the valve keepers, springs and all for this job? thank you!!

[antonyr123]

@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

[MJRPerformance]

@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

[antonyr123]

@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.