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Old 12-10-2015, 10:57   #1
Guy
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Perkins 107 overhaul help

New Perkins pistons come with the deck height uncut. The height is supposed to be, .0085-.012. How has everybody been skimming the tops of their new pistons? How much needed to be removed? The only thing I can think of is use an old cylinder liner as a holding fixture and use the sander with some 180 grit and try and keep it even. I wonder if the other overhauls I've seen on the docks or boatyards have bothered with this detail? I'm not taking my new pistons to some backyard guy with a lathe and that would be the only other choice.
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Old 12-10-2015, 17:08   #2
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Re: Perkins 107 overhaul help

How much Liner protrusion above head deck do you have?

How much piston protrusion above liner face?


Fit new bearings first.
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Old 12-10-2015, 17:53   #3
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Re: Perkins 107 overhaul help

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Originally Posted by shakey doug View Post
How much Liner protrusion above head deck do you have?

How much piston protrusion above liner face?


Fit new bearings first.
I don't have anything yet. I am tooling up for this job in Guatemala. Going by the manual you are supposed to trim the tops of the new pistons to + .0085 to .012 above the block top face. Yes with new bearings installed. They don't say how to cut the tops down. The new ones were machined on a lathe. I could sit there for a month and lap them on a flat plate too. I ain't gonna do that. The head gasket is thick enough to give enough clearance for any piston height probably. The specs and limits for piston height and valve depth keep the compression ratio very close to 22:1
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Old 12-10-2015, 18:36   #4
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Re: Perkins 107 overhaul help

To check clearances, install 1 or more pistons, put modeling clay on the piston top, install the head with your old gasket and rotate the crank twice so both valves cycle. Take off the head and with a thin rule, measure the clearances anywhere there is an impression in the clay. Or stick a wire into the clay. With a little wet paint on the clay, the wire will be bare where it went into the clay. Measure the wire.
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Old 12-10-2015, 18:54   #5
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Re: Perkins 107 overhaul help

Yeah, if this was a hot rod that would be the way. However there are specs for this engines piston height and valve depth that can be measured with tools. The cylinder head is overhauled and done and the valve depth is correct. These engines have flat top pistons and a flat cylinder head surface. There is no combustion chamber as we know it.
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Old 13-10-2015, 12:12   #6
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Re: Perkins 107 overhaul help

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Originally Posted by Guy View Post
Yeah, if this was a hot rod that would be the way. However there are specs for this engines piston height and valve depth that can be measured with tools. The cylinder head is overhauled and done and the valve depth is correct. These engines have flat top pistons and a flat cylinder head surface. There is no combustion chamber as we know it.
I know. I have one running a generator and I've done several others. I do my engines by the book. You appeared to want to skip some steps, try alternate ways, and I was hoping to stop you from causing some damage.
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Old 13-10-2015, 16:23   #7
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Re: Perkins 107 overhaul help

You might try posting that question on the Facebook Perkins 4-107/4-108 group. Several rebuilders in the group that have a lot of answers.
Ted..
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