To Oil or Not To Oil: T245 Connecting Rod Bushings

[Elwood]

So I'm trying to find a set of six connecting rods for the T245 230cid that are reasonably close in weight as part of my engine balancing project. Since these rods don't have balance pads, starting with a set of rods that are all close in weight is essential.

There are two basic groups of 230 rods: the forging no. 954408, which were used from 1942 through 1954, and are made in odd cylinder and even cylinder versions (the difference being on which side of the big end web the cylinder wall oiling squirt hole is drilled), and the later forging no. 1554530, which were used from 1955 through the end of production and which are drilled with squirt holes on both sides, and can therefore be used in either odd or even cylinders. The two designs can be mixed in the same engine, provided the squirt holes are in the correct locations.

However, in sorting through the rods that I've been collecting, I've discovered that there's a fair amount of weight variance within any group of the same forging number (and there's enough differences in the markings to suggest that Chrysler sourced the rods from more than one supplier or forging dies). There's also a difference in average weights between the two forging number groups, but more than could be attributed to the extra squirt hole in the later style.

Here's a typical 954408 rod:



And here's a typical 1554530 rod:



And from this angle, you can see the extra oil squirt hole in the later style 1554530 rod on the left:



After looking closer at the rods, I discovered what is likely the cause for at least some of the weight difference: the early rods have a cut in the small end to allow oil into the piston pin bushing, while the later rods do not have the cut:



After tearing down a couple of T245 engines, I've found a mix of the old and new rods, so it wasn't uncommon for them to be substituted during a rebuild.

I'm surprised that Chrysler engineering decided to eliminate the oil feed hole for the piston pin bushing. The only way to get oil into that bushing on the 1554530 rods is from the side, which doesn't seem very effective. Even new, high performance, H-beam rods for high horsepower V8 engines with floating pin bushings still have the oil hole on top of the small end.

If I end up using the 1554530 rods, I'm going to drill and chamfer an oil hole in the top of the small end. The replacement piston pin bushings that I have on hand have the hole, and it will remove a little bit of weight as well as increase the lubrication and durability of the bushing. Combined with a good polishing job on the sides of the beams, maybe I can add some strength and remove some weight to even them up. These rods are heavy enough as is.

[52 M-42]

Thanks, Elwood! Nice little piece of information on these engines for the rebuild file.

Thanks for sharing your knowledge and experience!

[Kaegi]

I agree the weight difference is mostly the cut in the small end. I would also ad the cut or dill a hole. I have only had rods with the cut that I can remember. mostly WCs in my flathead world.

[CREEPING DEATH]

IIRC, they are balanced by grinding the pistons and crankshaft counterweights. I have old hot rodding books that discuss the 230 and 'big block' sixes, and the part they thought most important was milling the head for extra compression and port-matching the manifolds to the block for better airflow.

CD

[T. Highway]

I agree with CD on shaving the head, matching the ports along with the gram balancing pistons and rods.

Bert

[w30bob]

Hi Guys,

I believe the con rods in the 230 are offset, so not only is it important to use the rods with the correct oil hole orientation, but the offset must be on the correct side as well. I remember reading somewhere that the offset is something like 30 thou.........does that ring any bells?

later,
bob

[Elwood]

Bob, I don't have a rod handy at the moment to measure, but I think the offset is more than 0.030. In the photo below, you can see how pronounced the offset is. I think it would be physically very, very difficult to assemble the rods/pistons/crankshaft with the offset on the wrong side, but easy to put an odd cylinder rod in an even cylinder or vice versa, thereby setting the oil squirt hole on the wrong side.

I posted this photo, and added the arrows, to show another problem that I've found with some of these Dodge / Plymouth 1554530 230ci rods: one of the cap bolt holes is drilled too close to the big end bearing bore, to the point that the cap bolt has actually intruded into the bearing radius, distorting the bearing shell. You can see at the arrows where the bolt hole actually intersects the bearing radius, and the metal of the rod is gone. Needless to say, these rods are scrap. The bearing life will be shortened, if it doesn't outright fail, and potentially the crankshaft journal will be damaged, too. Out of the one T245 I disassembled, I found three rods like this. Must have been machined on a Friday.



Here's the next step in the rod preparation process: polishing the beam sides. When the rods are forged, there's always some flash on the sides of the beams where excess metal is extruded from between the forging dies. This raised area forms an irregular surface, which can concentrate stress. Grinding down the forging flash, and smoothing the rod surface, eliminates the stress riser, and hopefully reduces the likelihood of rod failure.

Here's the rod beam before polishing:



And here's the beam after polishing (this one actually needs a bit more work, but it gives the idea of the before and after):



Once they're all polished, they'll be shot peened, then I'll press new bushings in the small end, then the caps will be ground slightly to reduce the size of the big end bore, then the big and small ends will be honed to the proper size, and finally I'll weight match them to all be within one gram (I hope; that tolerance might be difficult with these rods).