Slant Six Forum :: Early con rod orientation: still applicable?

To sum-up what we know:
*All Slant Six con rods had oil spurt holes drilled into them. ( and all other Chrysler con rods that I have seen)
*Early SL6 engines pointed the hole to the driver's side and that gave the cylinder / piston a lot of oil.
*Later SL6 engines were pointed towards the passenger side... and it is unclear if that was to give the cylinders less oil or to give the cam more oil.
*Cast crank SL6 engines have a spurt hole that is pointed near vertical and that oil hole position looks like it would give a good shot of oil to the bottom of the pistons.

So what should a SL6 engine builder do?
In my mind, this is more about piston cooling and piston pin oiling then "oil burning" or cam lubrication so it becomes an engine use or "application specific" decision.

When I build street SL6 engines... I point the spurt hole towards the cam.
(but I also make sure the piston pins have "positive" oiling)

For a high RPM endurance engine, I spurt the oil at the underside of the piston, to help cool it.
DD

Author:	Doctor Dodge [ Tue Dec 16, 2014 6:00 pm ]
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Quote: ... How does this help anyone?... And that is the point of the discussion... to help someone who is assembling a slant six. Someone who wants to know how to position the oil spurt hole in his engine. My 2 cents... The factory did what they did but today, where you point the con rod's oil spurt hole ends-up being the engine builder's decision. To sum-up what we know: All Slant Six con rods had oil spurt holes drilled into them. ( and all other Chrysler con rods that I have seen) Early SL6 engines pointed the hole to the driver's side and that gave the cylinder / piston a lot of oil. Later SL6 engines were pointed towards the passenger side... and it is unclear if that was to give the cylinders less oil or to give the cam more oil. Cast crank SL6 engines have a spurt hole that is pointed near vertical and that oil hole position looks like it would give a good shot of oil to the bottom of the pistons. So what should a SL6 engine builder do? In my mind, this is more about piston cooling and piston pin oiling then "oil burning" or cam lubrication so it becomes an engine use or "application specific" decision. When I build street SL6 engines... I point the spurt hole towards the cam. (but I also make sure the piston pins have "positive" oiling) For a high RPM endurance engine, I spurt the oil at the underside of the piston, to help cool it. DD

Author:	sandy in BC [ Tue Dec 16, 2014 6:04 pm ]
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Dan: Even though his facts are probably right. His delivery still leaves a bit to be desired.

Author:	nm9stheham [ Wed Dec 17, 2014 5:51 am ]
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This engine is using the standard flat CB606G rod bearings and the standard grooved-uppers-only main bearings; cast standard replacement pistons. This rebuild is an almost pure stock rebuild that will retain the 1 BBL Holley 1920; the only mod is to use a mild, low RPM torque cam (from Doug), so will not be a revver by any means and is just to be driven on the street as an enjoyable, original-car driver. The car is almost 100% original and I intend to keep it pretty much that way. The rationalilzation in my thinking was that if the later production engines survived in standard use with the oil hole towards the cam, then it ought to work on an early iron engine, since the rods, crank, block, and pistons did not change, and especially since the new stock replacement parts that you can buy are all the same regardless of year. I just ran across the Allpar article (with a significant attribution to Dan here) that includes the late '60 change in the rings' design to better manage oiling past the rings. So that kinda makes me think that perhaps the later oil spurt hole orientation was yet another step in that oil management process. The reasoning behind the TSB's that Dan references would be nice to know but perhaps that is lost to posterity. Head is going on this AM so the bottom end is all buttoned up this way. Hopefully this oil-hole thing will not cause my 1st engine assembly failure in 25-30 engines. And it HAS to be tons better than the gunk and varnish that we found inside, and the gasoline laden oil that we first drained from this engine; the PO took reasonable care of the car and fixed the bodywork nicely but was not mechanical; it had a carb leak that flooded into the intake each time the engine stopped. No wonder he never had to add oil....it was being 'auto-replenished' with gas! The bores were worn badly (took a .040" overbore to clean up after 60k total miles from new) but the crank was only down about .0005" from stock.. that was a surprise, considering the oil situation. Break-in in a coupla days! Thanks to all.

Author:	nm9stheham [ Wed Dec 17, 2014 6:15 am ]
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Quote: To sum-up what we know: All Slant Six con rods had oil spurt holes drilled into them. ( and all other Chrysler con rods that I have seen) Early SL6 engines pointed the hole to the driver's side and that gave the cylinder / piston a lot of oil. Later SL6 engines were pointed towards the passenger side... and it is unclear if that was to give the cylinders less oil or to give the cam more oil. Cast crank SL6 engines have a spurt hole that is pointed near vertical and that oil hole position looks like it would give a good shot of oil to the bottom of the pistons. So what should a SL6 engine builder do? In my mind, this is more about piston cooling and piston pin oiling then "oil burning" or cam lubrication so it becomes an engine use or "application specific" decision. When I build street SL6 engines... I point the spurt hole towards the cam. (but I also make sure the piston pins have "positive" oiling) For a high RPM endurance engine, I spurt the oil at the underside of the piston, to help cool it. DD Thanks for the comments Doug. I saw your photos from another thread on the positive pin oiling. Did not do that here on this stock rebuild; never even thought about it! (I've obviously been out of the garage for too many years.....) Do I understand you right that the later /6 rods for the cast cranks have the oiling hole nearly vertical? If so, then that says that pin oiling could have become a recognized issue. My early /6 rods have the hole inclined about 40 degrees from the axis of the rod, which would point to the cylinder walls, not the pistons. Have never done the oil hole from the oil ring groove even on race engines for rallying (70's vintage Opel 1.9L and 80's vintage Mitsubishi 2.6L turbo) and have never had any issues there. Buuut, those 2 engines both have oiling squirt holes in the rods that are nearly vertical. And these 2 engines also have holes on the under sides of the pin bosses. The later Mitsu intercooled 2.6's have oil squirter tubes direct off the main gallery to constantly shoot oil up straight up into the bores; I would guess those are indeed to cool the pistons for that 15-18 psi boost system.

Author:	Doctor Dodge [ Fri Dec 19, 2014 9:53 am ]
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I did some comparison between the forged crank & cast crank SL6 connecting rods. Looks like the cast crank con rod, with a "12:00" oil spurt hole position... still sends the oil somewhat "sideways". See the photos below showing some coat hanger wire, inserted thru the spurt holes to better show the angles. DD

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Author:	SlantSixDan [ Fri Dec 19, 2014 12:44 pm ]
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Quote: When I build street SL6 engines... I point the spurt hole towards the cam. Aluminum and iron blocks alike? (Thanks for speaking up!)

Author:	SlantSixDan [ Fri Dec 19, 2014 1:25 pm ]
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Quote: Dan: Even though his facts are probably right. His delivery still leaves a bit to be desired. Probably always will, though I continually strive to improve.

Author:	nm9stheham [ Fri Dec 19, 2014 3:25 pm ]
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Quote: I did some comparison between the forged crank & cast crank SL6 connecting rods. Looks like the cast crank con rod, with a "12:00" oil spurt hole position... still sends the oil somewhat "sideways". See the photos below showing some coat hanger wire, inserted thru the spurt holes to better show the angles. DD That is very interesting. Looking at the cast rod, the squirt hole will line up with the oil passage from the main when the journal is somewhere around 10 to 11 o'clock (going up towards TDC), and squirt hole at that point looks to be pretty much inline to hit the cam. For the forged rod, the squirt hole will line up with the oil passage to the journal at about 9 o'clock, and the squirt hole looks to be pointing below the cam. So did the cams tend to wear in the forged cam versions? Looks to me that in the forged crank rods with the squirt holes towards the cam, the cylinder wall oiling is at a low pressure, and so with the cast crank rods.

Author:	Doctor Dodge [ Fri Dec 19, 2014 3:28 pm ]
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Quote: Quote: When I build street SL6 engines... I point the spurt hole towards the cam. Aluminum and iron blocks alike? (Thanks for speaking up!) \ I have done Aluminium Block SL6 engine builds with spurt hole positions 3 different ways... Spurt hole to the driver's side. (per the FSM) Spurt holes to the cam side. Spurt holes plugged. (the Buster engine build) I never saw much difference or have enough data to make any claims. Base on all this inconclusive data... I think I will peen the spurt hole partially shut, in a way that helps defuse the oil shot into spray, on the next Aluminium SL6 I build for myself... and point the modified holes to the driver's side. DD

Author:	Dart270 [ Sat Dec 20, 2014 1:27 am ]
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Thanks, Doc. No excessive cam wear on any forged crank engine I have ever seen. I ran a 0.510", 250 @ 0.050" cam for 50k miles and tons of racing in my 64 Dart - worked fine when pulled. Lou

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