I had new hard valve inserts insstalled in a block. I had the machine shop cut the valve seats in the the new inserts, and had them reface the valves. They are 350 chevy exhaust valves. When I told the machine shop operator that i was going to hand seat the valves, he told me that since these were cut on a machine that I would not need to seat them. They would seat themsleves after a short time of operation. Is this a new procedure, or should I hand seat the valves? Thanks Ray.
I didn't hand seat mine.
If the seats were ground with a stone, lap the valves in. If they were cut with a carbide cutter, nothing more is necessary. Ground seats will have lines or look frosty. Cut seats will be smooth and near shinny. The grinding process for the valves is more precise and no further seating should be necessary for the valves unless the seats were ground. (see above)
"If they were cut with a carbide cutter" would that apply only to carbide cutter? How about the fluted steel seat cutter(old style)?
Thanks
Markg
I agree with your machinist. Those who insist on hand lapping valves may find this of interest. It is from the Operators Maintenance and Overhaul Manual - Continental Engines from Teledyne Total Power.
valve lapping
RAY your machinist is right hand lapping won't be necessary your valve seats and valve faces have already been precision ground.
Hand lapping is turning into one of those topics that 50%will argue for and 50% against personally i like it because it gives me a further visual aid to verify face to seat contact dimensions especially when i use a grinding stone on the seats.
Some people won't use the grinding compound for lapping because they feel no matter how well they clean up small traces of compound will remain to keep grinding away,so prussian blue could be used to verify contact surfaces and plain old oil could be put on the valve face or seat and the valve hand lapped this way which also verify's contact surface another unobtrusive method is a series of lead pencil marks around the valve face parallel to the stem and then hand lapped.
So you see where the hand lapping process goes it is more of a verification thing but i always hand lap with compound if a seat has been stone ground because i believe it leaves a smoother finish than the stones by themselves which can even with a new well dressed stone leave some large ridges that i don't like.Hope this helps. RAY
I agree with Ray's comments. I lap my valves to confirm complete contact. And, sometimes I've discovered contact was not complete and further lapping fixed things up.