02-11-2020, 09:30 AM
Steel seat cutters were also used but the seat surface has to be broken first or blunts cutters.
Grinding valves old style is very poor practice. It was done to remove pits from both valve and seat; wastefully reduced the block and formed a very undesirable step on the valve. And the valve not obliged to centre exactly. Production and modern recon technique is not to lap at all and often use an interference angle.
With my Seven used for extensive main road running, and operating a Javelin for decades I have done a lot of valve work. For reasons I did not understand at the time, the Javelin burned and sank innumerable valves and cracked heads. For those without the toys but with a lathe I describe my "tools". I use a one arm cutter to narrow valve seats. I have a series of dummy valves comprising mild steel screwed to rods and finished between centres to a very neat fit in the guides. These are used to lap the seats and regularly trued in lathe.
Valves reground in lathe chuck; with care many can be turned. Ideally should use a collet or do between centres as all chucks jaws wobble to some degree.
Esp for inlets seats can be placed high on the seat and valve cleared immediately below seating to give full breathing.
For the same lift 30deg gives more opening; considered beneficial with low lift valves
Grinding valves old style is very poor practice. It was done to remove pits from both valve and seat; wastefully reduced the block and formed a very undesirable step on the valve. And the valve not obliged to centre exactly. Production and modern recon technique is not to lap at all and often use an interference angle.
With my Seven used for extensive main road running, and operating a Javelin for decades I have done a lot of valve work. For reasons I did not understand at the time, the Javelin burned and sank innumerable valves and cracked heads. For those without the toys but with a lathe I describe my "tools". I use a one arm cutter to narrow valve seats. I have a series of dummy valves comprising mild steel screwed to rods and finished between centres to a very neat fit in the guides. These are used to lap the seats and regularly trued in lathe.
Valves reground in lathe chuck; with care many can be turned. Ideally should use a collet or do between centres as all chucks jaws wobble to some degree.
Esp for inlets seats can be placed high on the seat and valve cleared immediately below seating to give full breathing.
For the same lift 30deg gives more opening; considered beneficial with low lift valves