Yes, the hole is small - actually, it's a step-drilled hole - about 3mm at the inlet port and about 1mm at the discharge. But the hole is exposed to the oil supply twice per crankshaft rotation, multiplied by 6 rods.

I'm not as concerned about oil pressure as I am lack of cylinder wall lubrication.

And I'm not as concerned about cylinder wall lubrication as I am by the fact that folks who sell this stuff don't consider the consequences of changing operating parameters.... and seem content to accept whatever answer points them toward a sale..... which causes me to discount anything and everything they have to say. The crankcase is a fairly violent environment and there may be enough oil for the cylinder walls without the rod nozzles - so not drilling them might result in an overall advantage, but I would like to know that someone between the manufacturer/designer and user has considered the change and found the elimination of the nozzles acceptable.

I plan to take the rods to a machinist soon and see if he can drill the holes. It seems crazy to drill a new set of rods, but it also seems crazy not to do it without anecdotal evidence that they're unnecessary.

Frank

Here's some evidence that the idea of cylinder wall lubrication via rod squirters isn't so new - the rods on a 1958 Rambler V8 had squirters in the parting line of the rod bearing caps that each lubricated the opposite cylinder on the opposing bank:



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And John Erb of KB Pistons makes a sensible statement here when he suggests that OE piston skirts can catch major thrust face oil as they drop beneath the cylinder bore - leaving the curious to wonder what happens with shortened skirts such as the Wiseco pistons - and leading me toward the rationale for drilling the 3sx rods:

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It's incredible how much we can learn with curiosity and an open mind. I would never have thought to check if a piston skirt dropped below a cylinder bore or realized that it did so to pick up lubricating oil for the thrust face.

Frank

Piston wall squirter is defiantly not a new idea. They were needed with the oil and metals available then. With the oil we have now there is little need for the rods to be drilled.
And I would expect if it has not happened yet we will not be seeing the rod drillings for emission reasons. Part of why todays oil is changing.

That's an interesting take, Charlie.

I added something to the last post wrt piston skirt length and thrust face lubrication that should be considered when using short skirted pistons.

Frank

Any irregularity in a parts shape increases the stress and reduces the fatigue life of the part.

If an irregularity is in a thick section where the stress levels are lower the life cycle decrease caused by this ( increase in stress factor) does not reduce the overall life of the part.

However, it does imply that a section had to be made thicker to reduce the stress level in that area so that an oiling hole can be used.

That increases weight... increasing the overall stress on the rod and therefore reduces the parts life.

Every change in shape can be given what is known as a "K" factor. A sharp corner is the worst with a long smooth radius being the best.

When you drill a hole in the rod you get a stress point. For a race rod where the goal is maximum strength, maximum fatigue life and minimum weight. Since the anticipated loads are high it makes good design sense to eliminate the oil hole and reduce the weight of the part.

Also a typical race engine is not spending a lot of time at idle and will in general have wider bearing clearances that throw more oil.

As with any change the only real way to know is to test the setup and see how well it holds up. You can make an educated guess, but in the long run it comes down to testing.

Since your motor is not a high RPM NA cammed out screamer, rod strength and loading is less of an issue. ItÆs the forces generated with a change in direction that is really hard on rods and that force goes up with the square of the engines speed. With a boosted motor the new loads are mostly in compression and the force to pull the rod down does not increase significantly ( not like changing the RPM from 6000 to 9000 would).

As a reference I have worked on Ducati motor that titanium rods that did not even have tangs or notches to hold the bearing shells. They were held in place only by the compression of the bearing shells by the cap.

The also were not drilled for cylinder wall oiling and the motor held up just fine at 15,000 RPM.

If I were to put a hole in a con rod I would consider finding a mold shop with a wire EDM.

Also when the stress levels are below a certain level the number of stress cycles a part can take becomes infinite. In he case of our motors thats typicly the case.

On my Ducati example not so much.


Kevin

I thought about the stress issues you raise wrt drilling, but also think that it won't be an issue at 6,000 rpms - although the metal thickness at the point where the hole would be drilled is less than what is on the OE rod. I still think it should be ok if the inlet port is chamfered.

I also thought about dynamic balance issues from removing the drillings weight from only one side of the rod, but I doubt if that's much of an issue either. The factory rod has a cast bump at the nozzle that adds back some of the weight removed by the drilling, but I think it serves more as a nozzle extension and/or a less angular surface to drill into for the nozzle bore.

I installed a 10:1 Diamante rod and piston in an open block and turned the crankshaft to BDC to see how far the skirt is exposed - it's about 0.500":


Then, I compared an OE piston to a Wiseco and found the same 0.500" differential in skirt length:


So - that removes one source of potential cylinder wall lubrication.

There's a very good engine machinist in town - I've never used him, but I've heard a lot about him and everyone I've talked with says he's extremely good with race engines. I like the fact that he works alone and no one in his shop does any machine work but him. He also has the only align boring equipment in town, so I need to get to know him anyway. I'll see if he can shed any light on it - my instincts tell me to drill the rods if it can be done without harm to them.

I wouldn't know where to begin to look for EDM drilling equipment around here, but that would be neat to watch.

Frank

http://www.fordmuscle.com/forums/al...issing-opening-cylinder-wall-oiling.html

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Good read on rod side clearance and wall oiling.... Larry says you dont need it on the SB mopar.

You can get some oil up to the walls with a relief on cheek of the rod. BTW... Larry Shepard is a legend.

Kevin

That bump may have more to do with compensating for the loss of fatigue strength fact than for weight matching the rod side to side.

Kevin

Yes - forged - my goof.

Frank

The article on rod side clearance is interesting.

By comparison, the 6G72 designed clearance is much tighter than 0.017" at 0.0039 - 0.0098" with a service limit of 0.016". Maybe that has something to do with why the factory used the rod squirter if the tighter clearance leads to a dry cylinder wall.

Dunno...... but you're probably right - in the end, I have to make a best guesstimate and see what happens. In the meanwhile, the more input information the better. Thanks!

Frank