340 cylinder honing question

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1967fishguy

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I acquired my 340 35 year's ago with motor work just having been completed. It's been used lightly of course over the years with no major work having been done since. Compression is 165-175 across the board. I've noticed that my cylinders are absolutely smooth, what does this signify since there is no cross hatch in the bores, is this normal, special rings perhaps?
Just joined and this is my first post, happy to be here!
Thanks for any help.
 
If you are reconditioning the motor then you will need to measure the cylinder wall taper to insure it falls within specs, if it does, then hone the cylinders if new rings are installed. Vertical deep scratches in the cylindere walls are also an indication of possible oil consumption so check each cylinder carefully. If all looks good you are probably safe to leave bottom end alone.
 
Welcome aboard. Lots of good people on here and lots of opinions.
Good luck on your 340.
Syleng1
 
depending on what your current or future plans are for the motor, i'd say let that sleeping dog lie.

are you just doing a refresh/gaskets or are you upgrading things and stuffs while you've got it all apart?
 
If there is no cross hatch in the bores, for whatever reason, there is a veeeeeery good chance you will glaze the bores if you do not hone them first.
Once glazing happens, is very difficult to see...& fix.
 
Measure, measure, measure; and check your ringlands for shiny shiny wear.

Every .001inch of bore-taper will change the ring gaps by a tic over .003inch
Those changing gaps will cause the rings to move into and out of the lands, every time the piston goes up and down, eventually wearing them out, and losing ringseal. Loss of ringseal equals loss of cylinder pressure, which equals; loss of power at WOT, reduced idle-vacuum, increased crankcase pressure, oil-burning, poor fuel economy, decaying throttle response, and not to overlook the possibility of oil-dilution, leading to bearing failure.
I mean a stinking lot can happen in 35 years.

Just measure it.............. it'll be fine, right?
 
Unless the motor was sealed in plastic, with the rocker shafts loosened/removed, so the valves are all closed, - the motor will breathe.
Thru open valves, the daily heating/cooling, the humidity, will actually suck in and expel air.
The cylinders open to atmosphere often have a rusty area on the cylinder walls.
We had an example here not long ago, engine sat x yrs, upon disassembly coupla cyls rusted badly .
I've seen it a few times personally, particularly marine engines, with wet exhausts.
Borescope each cyl if big $$$ involved.
Good luck. I'll try to find link to pic.
 
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