Re: Cylinder 4 - low compression after valve job
Are you talking about the bump on the top of the piston? Doubt it would do anything to compression.
Is it possible one of the valve lash adjusters is stuck? If so, it could be holding the I or E valve off its seat, leading to poor compression.
You should be able to lean on the support end of the cam follower, pushing downward hard for a while. I like to use a hammer handle, putting the wooden end on the top of the follower. The follower should collapse a bit, perhaps .050".
If you cannot compress it, you can work the follower out from under the cam, off the valve stem and the follower, and pull the follower. It may be sticking due to deposits, but can be disassembled if you want to take the time. They should be replaceable without any special consideration. No 'size', they are all the same. Used would be cheaper.
If you don't want to do that, get a Tbsp or two of oil, put down the spark hole, and check compression. If it comes up a lot, i.e., from 60 to 130-150,l your rings are likely leaking. Not good. If it stays the same, general thought is the valves are not seating. That is, if the head gasket is functional.
tom
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