I need some guidance on hand lapping some valves
06-07-2008, 05:59 PM
#1
Drifting
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I need some guidance on hand lapping some valves
I got some nice used intake valves from a 30k mile head to replace the bent ones. The face of the valves are nice and shiny. When lapping how do I know they are done? Is it that the top and bottom off the face are still shiny and that the middle of the face is rough looking? What does it mean if all of the face is rough looking?
06-07-2008, 06:46 PM
#2
Nordschleife Master
Rough looking is from corrosion = not good.
When you lap the valves, don't use alot of pressure, or you'll just push all the paste out. Just use slight pressure, and go until it sounds and feels smooth. Then wipe off the paste from both the head, and valve. The valve and seat should both be smooth all the way around, and have a matte finish. If there are even a few small pits in either the valve or seat, then do it again. It should be perfectly smooth. (On the valve, the only perfectly smooth part will be where the valve hits the seat .... only about a 1/8 in wide spot) To check your work, put all the valves in (no springs, just set in), and some old spark plugs. Then rig the head so it sits level, upside down ... combustion chamber up. Fill the chambers with carb cleaner, and come back in the morining. If they're all still full, then NO LEAKS! ... if one of them has a leak, then you gotta find it. Check the intake and exhaust ports for wettness, and the spark plug hole too.
There are alot of people that will tell you to just go have the work done for you at a shop. Of course thats an option, but lapping works great. Its kind of old fashioned, but race engine builders STILL do it to this day. Its an easy do-it yourself thing, and makes you feel good.
ok, I'm done talking now
When you lap the valves, don't use alot of pressure, or you'll just push all the paste out. Just use slight pressure, and go until it sounds and feels smooth. Then wipe off the paste from both the head, and valve. The valve and seat should both be smooth all the way around, and have a matte finish. If there are even a few small pits in either the valve or seat, then do it again. It should be perfectly smooth. (On the valve, the only perfectly smooth part will be where the valve hits the seat .... only about a 1/8 in wide spot) To check your work, put all the valves in (no springs, just set in), and some old spark plugs. Then rig the head so it sits level, upside down ... combustion chamber up. Fill the chambers with carb cleaner, and come back in the morining. If they're all still full, then NO LEAKS! ... if one of them has a leak, then you gotta find it. Check the intake and exhaust ports for wettness, and the spark plug hole too.
There are alot of people that will tell you to just go have the work done for you at a shop. Of course thats an option, but lapping works great. Its kind of old fashioned, but race engine builders STILL do it to this day. Its an easy do-it yourself thing, and makes you feel good.
ok, I'm done talking now
06-07-2008, 07:14 PM
#4
Nordschleife Master
Yeah, that looks good. Just make sure its smooth all the way around,
And look for the same on the valve seat in the head. It should have an even width around it too.
Don't forget the exhaust valves. Do them all while you're in there.
And look for the same on the valve seat in the head. It should have an even width around it too.
Don't forget the exhaust valves. Do them all while you're in there.
06-07-2008, 07:20 PM
#6
Nordschleife Master
OH and make sure that you put your engine oil of choice on the valve stems....you don't wanna put any additional wear on the guides when your lapping!!!!
put more oil on the stems before you put the springs back on too. The guides need the lube on the initial start up.
put more oil on the stems before you put the springs back on too. The guides need the lube on the initial start up.
