So this got slightly put on the back burner for a bit as i had some other fabrication jobs on, but finally got back at it this weekend.
first job was to hone the bores to their final state so i could measure them, and then gap the rings and check the piston dimensions accordingly.
the flex hone is an awesome piece of kit - so easy and quick to use, and produces a finished far better than any 3 legged honing tool ive used in the past. the idea is that it contours to any size or shape (within reason obviously) and produces a honing procedure and a plateau hone all in one. This means that the rings have the bare minimum amount of bedding in work to do knocking the sharp peaks off the surface which means less cylinder material in the oil, less ring wear as they bed in, and compression coming nearly from the first few pulls on the dyno. with a standard hone, that a general machine shop might do, the bore surface has an RA finish that has sharp peaks that the rings have to wear down in order to bed in - not good for rings, or the lubrication system! the plateau effect knocks off these peaks for the rings, but leaves the valleys, with a surface keyed enough to hold oil but not too rough to wear the rings. A plateaued bore surface will stabilize after about two hours of running - the rings will seat very quickly and experience almost no further wear. A more conventional surface finish, by comparison, may take anywhere from three to 12 hours to seat in depending on the grade of stones used.
a great trick to test this is to rub a cotton ball along the cylinder, and take a photo with a flash on. with a standard hone you will see a load of micro fibres from the cotton ball where the microscopic sharp peaks have grabbed the cotton. with the cylinders plateau honed, you can still see a scored surface to the eye, but it wont grab the cotton and will feel perfectly smooth to the touch.
it took me about 20 mins to complete the whole process, i think the finish speaks for itself.
perfect 45degree crosshatch.
before
after
the obvious down side to this is that the honing oil sprays EVERYWHERE when running it in and out of the cylinder, along with all the nasty cast iron particles. the resulting solution is an engine block drenched in grey oily abrasive paste - yuck.
obviously the clean up is vitally vitally important as you can imagine - hot soapy water and a scrubbing brush for at least 15 mins. and when it looks clean, scrub it again for another 15 mins. the iron particles will be embedded in the valleys, which need to be scrubbed out with a still bristle brush and loads of really hot really soapy water. not to mention every other orifice it can find its way into.
cylinder cleaning brushes really come into their own here.
after the block was washed and dried it was time to gap the rings.
I went for Mahle Ductile iron rings, a good upgrade on the more fragile and less ductile standard grey cast iron rings, perfect for moderate performance/heavy duty use.
the specs for the engine in question is .3mm to .5mm on both the compression rings - so i went about seeing what i had.
i spent alot of time swapping rings from one cylinder to another to get as close to the figure i wanted - ideally .35mm to .4mm. I'm not sure i would be too happy running .3mm as this engine is going to get hot autotesting - the chances of the rings butting and scuffing the cylinders increases.
I'm also going to open up the second ring about 0.05mm more than the top to prevent gas build up between the top and second rings.
This can cause the top ring to flutter or bounce and lose its seal.
with ALOT of fitting, removing, testing and filing, I'm pretty much there with .4mm on the top ring and .45mm on the second ring.
the next job was to test fit the crank to measure the bearing clearances with plastiguage - if the clearances are a tiny bit sporadic, its good practice to swap the tightest one for the loosest one and vice-versa - it takes alot of time, but is worth it in the end for uniform clearances.
for this engine I'm looking for 2 thou, which luckily was nearly spot on - the front main is slightly larger is between 2 and 2.5, perhaps 2.3/2.4 thou, so I'm happy with that.
so i was able to fit and torque the crank on the main line.
i also stripped the new oil pump, deburred all the sharp cast edges on the gears and the housing with a small fine mill file, and packed it with vaseline
so it draws oil pressure instantly on start up.
some other tasks done was to hone the gudegon pin bush, and polish the pins on the lathe.
over the next few evenings i need to lighten, balance and polish the rods, caps and pistons.
the pistons are MAHLE forged so will likely be less than .5g of each other
first job was to hone the bores to their final state so i could measure them, and then gap the rings and check the piston dimensions accordingly.
the flex hone is an awesome piece of kit - so easy and quick to use, and produces a finished far better than any 3 legged honing tool ive used in the past. the idea is that it contours to any size or shape (within reason obviously) and produces a honing procedure and a plateau hone all in one. This means that the rings have the bare minimum amount of bedding in work to do knocking the sharp peaks off the surface which means less cylinder material in the oil, less ring wear as they bed in, and compression coming nearly from the first few pulls on the dyno. with a standard hone, that a general machine shop might do, the bore surface has an RA finish that has sharp peaks that the rings have to wear down in order to bed in - not good for rings, or the lubrication system! the plateau effect knocks off these peaks for the rings, but leaves the valleys, with a surface keyed enough to hold oil but not too rough to wear the rings. A plateaued bore surface will stabilize after about two hours of running - the rings will seat very quickly and experience almost no further wear. A more conventional surface finish, by comparison, may take anywhere from three to 12 hours to seat in depending on the grade of stones used.
a great trick to test this is to rub a cotton ball along the cylinder, and take a photo with a flash on. with a standard hone you will see a load of micro fibres from the cotton ball where the microscopic sharp peaks have grabbed the cotton. with the cylinders plateau honed, you can still see a scored surface to the eye, but it wont grab the cotton and will feel perfectly smooth to the touch.
it took me about 20 mins to complete the whole process, i think the finish speaks for itself.
perfect 45degree crosshatch.
before
after
the obvious down side to this is that the honing oil sprays EVERYWHERE when running it in and out of the cylinder, along with all the nasty cast iron particles. the resulting solution is an engine block drenched in grey oily abrasive paste - yuck.
obviously the clean up is vitally vitally important as you can imagine - hot soapy water and a scrubbing brush for at least 15 mins. and when it looks clean, scrub it again for another 15 mins. the iron particles will be embedded in the valleys, which need to be scrubbed out with a still bristle brush and loads of really hot really soapy water. not to mention every other orifice it can find its way into.
cylinder cleaning brushes really come into their own here.
after the block was washed and dried it was time to gap the rings.
I went for Mahle Ductile iron rings, a good upgrade on the more fragile and less ductile standard grey cast iron rings, perfect for moderate performance/heavy duty use.
the specs for the engine in question is .3mm to .5mm on both the compression rings - so i went about seeing what i had.
i spent alot of time swapping rings from one cylinder to another to get as close to the figure i wanted - ideally .35mm to .4mm. I'm not sure i would be too happy running .3mm as this engine is going to get hot autotesting - the chances of the rings butting and scuffing the cylinders increases.
I'm also going to open up the second ring about 0.05mm more than the top to prevent gas build up between the top and second rings.
This can cause the top ring to flutter or bounce and lose its seal.
with ALOT of fitting, removing, testing and filing, I'm pretty much there with .4mm on the top ring and .45mm on the second ring.
the next job was to test fit the crank to measure the bearing clearances with plastiguage - if the clearances are a tiny bit sporadic, its good practice to swap the tightest one for the loosest one and vice-versa - it takes alot of time, but is worth it in the end for uniform clearances.
for this engine I'm looking for 2 thou, which luckily was nearly spot on - the front main is slightly larger is between 2 and 2.5, perhaps 2.3/2.4 thou, so I'm happy with that.
so i was able to fit and torque the crank on the main line.
i also stripped the new oil pump, deburred all the sharp cast edges on the gears and the housing with a small fine mill file, and packed it with vaseline
so it draws oil pressure instantly on start up.
some other tasks done was to hone the gudegon pin bush, and polish the pins on the lathe.
over the next few evenings i need to lighten, balance and polish the rods, caps and pistons.
the pistons are MAHLE forged so will likely be less than .5g of each other