BB Mopar machining tips
Posted: 28 Aug 2005 17:40Anybody interested in BASIC some info and opinions on machining ? Might be very useful for those contemplating supervising or building their own engines, especially those who have limited access to info or specs.
Example; "magnum" or the 440 H.P.(non 6 pk) orange painted engines, went down a side assembly line. While basically the same parts were used in '69 from the low-perf brethren, 906 heads, .050" Flat tops etc., and assembled, some additions were a windage tray, better valve springs and hotter cam, it's also interesting to note than mother installed cranks ground to the "lowside" of the specs to provide an additional .001" vertical oil clearance to the bearings, on this "side" assembly shop. Remember, Mopar was warranty'ing these engines and wanted some insurance oil clearance based upon the tweaked performance.
Learning curve here, should be to target "lowside" crank grinds for performance engines. This allows for targeting "in range" housing bores on the rods and mains when machining to provide good bearing crush, and still achieve optimum bearing clearances without taking the bores outside their range to get the clearance.
Put the clearance ON THE CRANK ! DO NOT TAKE THE RODS OR MAIN BORE SADDLES ABOVE RANGE !
Tolerance Example; rod throws can be 2.374-2.375 (spec)when standard. You want 2.3740 +/_ .0002". Same goes when grinding .010". You want 2.3640 +/_ .0002". This will allow your rod resize to be maintained within the specified 2.5000" - 2.5005" for good bearing crush, and provide adequate bearing clearance.
You'd be amazed how many shops will simply take the rods out to say 2.5010" ARRGGGHHH! just to get some clearance, because the crank was too big at 2.375" on the throw and they're too lazy to make it right, or they leave the rods "in" range, and you end up with .001" clearance or less. Not good if you're gonna drive it like you're MAD AT IT ! whilst making some snotty power.
Same curve on the mains, different specs of course.
Next up;
Bearing eccentricity, the "p" or "h" or "v" after the part number on the brg box. Example Clevitte rod brg # CB 527 "P". What does it mean ?
Example; "magnum" or the 440 H.P.(non 6 pk) orange painted engines, went down a side assembly line. While basically the same parts were used in '69 from the low-perf brethren, 906 heads, .050" Flat tops etc., and assembled, some additions were a windage tray, better valve springs and hotter cam, it's also interesting to note than mother installed cranks ground to the "lowside" of the specs to provide an additional .001" vertical oil clearance to the bearings, on this "side" assembly shop. Remember, Mopar was warranty'ing these engines and wanted some insurance oil clearance based upon the tweaked performance.
Learning curve here, should be to target "lowside" crank grinds for performance engines. This allows for targeting "in range" housing bores on the rods and mains when machining to provide good bearing crush, and still achieve optimum bearing clearances without taking the bores outside their range to get the clearance.
Put the clearance ON THE CRANK ! DO NOT TAKE THE RODS OR MAIN BORE SADDLES ABOVE RANGE !
Tolerance Example; rod throws can be 2.374-2.375 (spec)when standard. You want 2.3740 +/_ .0002". Same goes when grinding .010". You want 2.3640 +/_ .0002". This will allow your rod resize to be maintained within the specified 2.5000" - 2.5005" for good bearing crush, and provide adequate bearing clearance.
You'd be amazed how many shops will simply take the rods out to say 2.5010" ARRGGGHHH! just to get some clearance, because the crank was too big at 2.375" on the throw and they're too lazy to make it right, or they leave the rods "in" range, and you end up with .001" clearance or less. Not good if you're gonna drive it like you're MAD AT IT ! whilst making some snotty power.
Same curve on the mains, different specs of course.
Next up;
Bearing eccentricity, the "p" or "h" or "v" after the part number on the brg box. Example Clevitte rod brg # CB 527 "P". What does it mean ?
