At The Back Of The Pack
Arm chair racerAt the back of the pack
Does anybody know where i can find dimensions for this piston? I tore my top end down the cylinder looks perfect would just need a hone to put cross hatching back into it. Looking for the dimensions so i can measure my cylinder and if it is not egg shaped i may be able to get away without having to bore it if its within specs for the piston.
At The Back Of The Pack
Arm chair racerAt the back of the pack
Ok i measured 3 dif spots through the bore of the cylinder then i clocked it 90 degrees and measured the same 3 spots the smallest measurement i got was 2.5595 and the biggest i got was 2.5605
FACT ! I have no edit button
Arm chair racerThe day begins with 3WW
That is easily reusable.Originally Posted by Fullsizechevy9
FACT ! I have no edit button
Arm chair racerThe day begins with 3WW
You don't need dimensions for the piston, you only need to know what the clearance between the piston and the cylinder are.
For recreational use, you could easily get away with as much as .003" clearance.
At The Back Of The Pack
Arm chair racerAt the back of the pack
So i should be able to buy a hone put some cross hatch back into it and order the 65mm piston
At The Back Of The Pack
Arm chair racerAt the back of the pack
This motor doesnt hardly look used no wear on the rocker arms at all they look brand new would you recommend buying the hardfaced rockers or could i use these they look brand new
At The Back Of The Pack
Arm chair racerAt the back of the pack
Well scratch that i just whipped it out with some fine sand paper on a die grinder have an attachment i made you put sand paper on and it spins the paper true kind of like a hone i did it very light just enough to scratch the surface without changing the dimensions well i can now see very small lines that run vertical through the bore i think i will just go with the 65.5mm piston to be on the safe side incase it doesnt clean up with hone i can machine a fixture in my lathe to hold the cylinder true with a backing plate and some long studs through the 4 holes in the cylinder i have seen it done this way before using the gasket surface area and the sleeve that sticks out the cylinder i would bore a hole in the fixture for that to fit snug that would take care of the o.d. and the backing plate would pull the cylinder square so it would all run true
At The Back Of The Pack
Arm chair racerAt the back of the pack
Use as big of a boring bar i can get away with shouldnt have to worry about chatter
FACT ! I have no edit button
Arm chair racerThe day begins with 3WW
Never, ever use sandpaper on a die grinder inside a cylinder bore.
The fine lines may be completely irrelevant. It depends on how deep they are. Fine lines will have little affect and can even typically be removed by honing the cylinder. It is best to use an "xlnt" quality 3 blade hone to do this with.
If you are a perfectionist, then to achieve the optimum trueness when boring a cylinder, a "torque plate" should be used and the cylinder can even be heated to operating temp before boring.
.
At The Back Of The Pack
Arm chair racerAt the back of the pack
Good to know i just barly scuffed the surface glad i did or i would have not seen the lines 1 catches my fingernail pretty sure it would be out of specs for the 65mm piston by time it cleaned up and probably would take forever to hone out idk y i said backing plate i meant torque plate it bolts the cylinder to the fixture and keeps it square that is what your talking about right and yes i have some temp stick i can heat it to operating temp before boring being that metal does expand and contract as it heats and cools not sure how much at that temp but when machining bearing fits i somtimes get .002 contraction as it cools easily also do i need a certain grit hone or is that what the xlnt is im going with the 65.5mm to be on the safe side i want the bore to be clean free of any vertical lines if i bore the cylinder to 65.5mm the piston should already have the clearance built in right clarence?
FACT ! I have no edit button
Arm chair racerThe day begins with 3WW
a torque plate is completely different.
pre heating the cylinder some for boring is overkill and complicated so don't worry about it.
never assume the piston will be the correct size. always, always, always get the piston first then measure it.
it can take around 5 minutes to remove around .0001" from a cylinder with a hand hone.
.
.
FACT ! I have no edit button
Arm chair racerThe day begins with 3WW
[QUOTE=Fullsizechevy9;1498635]i have some temp stick i can heat it to operating temp before boring being that metal does expand and contract as it heats and cools not sure how much at that temp but when machining bearing fits i somtimes get .002 contraction as it cools easily.
If you have a cylinder that has a bore that changes size by .002" from hot to cold it has serious problems.
Also, I have never seen anyone get a hole they are machining so incredibly hot that it will close up .002" after it cools, but apparently it can happen in some cases.
.
At The Back Of The Pack
Arm chair racerAt the back of the pack
Wasnt talking a cylinder just saying in general metal expands and contracts with heat how much heat i have no clue never measured temps but i have machined plenty things that shrunk after it cooled thats why with tight tolerences i always allow it to cool first depends on the application and yes i have sanded my ass off just for a couple thousenths bearing fits on an o.d. i always leave a thousenth or 2 big and polish within the tolerence im allowed. I will def get the piston before any machine work and i will research torque plates amd see what i come up with but in theory if my fixture is machined true and the plate i use to sandwich the cylinder with is true it should be about as true as it will get i will have to check for warpage on the mating surfaces first but i doubt this motor ever got that hot
At The Back Of The Pack
Arm chair racerAt the back of the pack
I also use a die grinder with sandpaper for holes with tight tolerences leave them a couple thousenths small and polish them in and can get it pretty concentric within a .001 which is plenty good enough for a bearing just have to do a little then stop and measure keep on til its right usually have .0015 to play with on bearing fits depends on the application low speed or high speed would never do that with a motor but works for what we do
At The Back Of The Pack
Arm chair racerAt the back of the pack
I looked into a torque plate thats what i was talking about making so i could bolt the cylinder to the fixture thats the only way i have seen them done is with those plates keeps it square and mimics the force that will be applied when the engine is assembled so you get an accurate reading when machining the bore
Reply With Quote