Originally Posted by Twin-shocker
In some cases there is no need for any sort of machining at all. Removing head and base gaskets is all you will need. I would be very cautious over using someone offering to machine heads on the basis of solder, for the simple reason that if the solder test isnt done perfectly then neither will the head machining. Taking the motor to someone who knows exactly what they are doing is the only real option for this type of work, but in most cases closing the clearance by the 1mm that will be provided by removing the gaskets, will be all thats needed on roadgoing motors.
if you remove the base gasket you change exhaust port height and to a lesser effect intake/boost port height.. machining the head (or removing head gasket/using thinner head gasket) is the only way to modify squish without affecting port timing. most water cooled motors (and many air cooled) don't have head gasket, so head machining is the way. you can modify squish by changing the base gasket stack, but it will effect port timing, sometimes enough to have a drastic effect on the top end rpm - not always in a good way.. you can easily lose massive top end hp if your exhaust port doesn't open all the way due to no base gasket.
solder check works fine. there is a reason he asks for 3 solder samples. repeatability. it's kinda hard to do it wrong.
also, most are not just decking the head. the head gets reshaped to get better squish, and optimum combustion chamber volume. there's more to it than just turning off some of the head to cylinder mating surface.