L79-870 block - crankshaft assembly spec info needed.
05-16-2010, 04:31 PM
#1
Burning Brakes
Thread Starter
L79-870 block - crankshaft assembly spec info needed.
What is the required clearance between the crank journals and bearings for the L79/870 block? Also what is the torque spec.s for the main caps bolts? Thanks
05-16-2010, 09:57 PM
#2
Le Mans Master
I like .0015 in a perfect world. Great oil pressure, idle and high RPM. Old school builders wanted more like .0025 to .003 and sometimes more for high RPM.
OEM Specs allow .0005 to .0032. Too tight to too loose in my opinion.
Very few blocks are perfect but modern engine bearings from Federal-Mogul or Clevite hold specs very well and you can run them tight with great success.
The more clearance you run the more oil bleed you have. Oil bleed shows up when your oil pressure drops off at idle. Oil pumps have enough volume at 400 RPM to already be hitting the by pass mode and pressure should not change. If it does you have too much clearance for the pump to keep up at idle. High volume pumps can mask this oil bleed issue by pumping more oil.
A little oil bleed is necessary to lubricate the pistons from connecting rods, as the crank rotates the connecting rods spill a little oil on the cylinder walls. Loose bearings, .003 or more will cause the piston rings to work way too hard scraping excess oil and may cause oil consumption.
OEM Specs allow .0005 to .0032. Too tight to too loose in my opinion.
Very few blocks are perfect but modern engine bearings from Federal-Mogul or Clevite hold specs very well and you can run them tight with great success.
The more clearance you run the more oil bleed you have. Oil bleed shows up when your oil pressure drops off at idle. Oil pumps have enough volume at 400 RPM to already be hitting the by pass mode and pressure should not change. If it does you have too much clearance for the pump to keep up at idle. High volume pumps can mask this oil bleed issue by pumping more oil.
A little oil bleed is necessary to lubricate the pistons from connecting rods, as the crank rotates the connecting rods spill a little oil on the cylinder walls. Loose bearings, .003 or more will cause the piston rings to work way too hard scraping excess oil and may cause oil consumption.
Last edited by Westlotorn; 05-16-2010 at 09:59 PM.
