Crankshaft Stiff to Rotate with Pistons
Posted: Tue Sep 05, 2017 9:02 pm
Currently building up the bottom end of the twink. Please excuse the writing style, but I've tried to be clear with the steps ive taken.
Crank reground and straight. Spins easily from the snout when the main bearings are torqued down. End float good.
Pistons are new QED type with new rings, all gapped between 9-14thou (average 11thou)
Block is also new, and has been bored/honed. Piston to bore clearance of 3-4thou for all cylinders.
Installed pistons, rotating each time to check for increasing tightness working along 1 through to number 4. Seemed to require a fair push to get them to move down the bores. All rod caps torqued up correctly and correct sequence.
Once assembled, the short block required about 15-18 ft-lb on the wrench to break the stiction and perhaps a little less to keep rotation. Particularly tight when mid-stroke. This seems a lot to me. (furious kicking of tools, this engine has been a nightmare). I was told less than 10 lb-ft is sensible.
Suspect the stiction is coming from the pistons, rather than the bearings. Removed all the pistons, and the rings (broke one bollocks) Re-inserted all pistons minus rings and torqued down rods again. Rotating assembly is seemless with no tight spots anywhere. Can rotate the crank by the snout, ruling out tight big end bearings or mains.
So, breathe, my question is. WTF is going on? Everything checks out, so should I just build it and go? Also, since ive installed and removed the new rings (and I was disturbed that one of the compression rings broke), do I need to junk those rings and replace them all? I know they are brittle and dont take kindly to being man-handled, and I would hate to have a ring let go for the sake of ?100.
This engine is taking me to dark places .
Thanks for any input
Crank reground and straight. Spins easily from the snout when the main bearings are torqued down. End float good.
Pistons are new QED type with new rings, all gapped between 9-14thou (average 11thou)
Block is also new, and has been bored/honed. Piston to bore clearance of 3-4thou for all cylinders.
Installed pistons, rotating each time to check for increasing tightness working along 1 through to number 4. Seemed to require a fair push to get them to move down the bores. All rod caps torqued up correctly and correct sequence.
Once assembled, the short block required about 15-18 ft-lb on the wrench to break the stiction and perhaps a little less to keep rotation. Particularly tight when mid-stroke. This seems a lot to me. (furious kicking of tools, this engine has been a nightmare). I was told less than 10 lb-ft is sensible.
Suspect the stiction is coming from the pistons, rather than the bearings. Removed all the pistons, and the rings (broke one bollocks) Re-inserted all pistons minus rings and torqued down rods again. Rotating assembly is seemless with no tight spots anywhere. Can rotate the crank by the snout, ruling out tight big end bearings or mains.
So, breathe, my question is. WTF is going on? Everything checks out, so should I just build it and go? Also, since ive installed and removed the new rings (and I was disturbed that one of the compression rings broke), do I need to junk those rings and replace them all? I know they are brittle and dont take kindly to being man-handled, and I would hate to have a ring let go for the sake of ?100.
This engine is taking me to dark places .
Thanks for any input