Thread: old connecting rods

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I would imagine that after they were converted the rods to floating they would recondition the rods. They should be miked after they have been reconditiond
for bearing clearance. Yes full float is better, I think I would order the rods from scat.
Kurt

I was typing while Pat was posting. I'll let this ride anyway.....

Pressed pins are used in probably 99.9% of automotive engines because it's cheaper and quicker than floating pins. In a motor that will be put together and run for several seasons without coming apart, pressed pins are the way to go. If the motor is a race motor that will be coming apart for inspection on a regular basis, then floating pins might be more attractive.

Let's start with a primer. The bore on the small end of the rod on a pressed pin rod is bare steel. When the motor is being assembled, the rod is laid in a heating apparatus that heats the pin end, swelling the inside diameter of the bore to that a wrist pin can be pushed through the rod. As the rod cools, the bore gets smaller and locks the wrist pin to the rod, holding it in place laterally and circumferentially. The piston used with this arrangement can be machined for wrist pin locks, or it cannot be machined for wrist pin locks. It doesn't matter either way, because the wrist pin is locked to the rod and cannot move. If the piston is machined for locks, you simply don't use them.

The bore on the small end of the rod on a floating pin rod has been bored out to accept a thin-wall bronze bushing which is pressed into the pin end of the rod. The wrist pin rides on this bearing material and is free to rotate within the rod or move laterally within the rod. Therefore, you must use some means of keeping the wrist pin from moving laterally and riding on the cylinder wall where it could score the wall. This is where piston lock rings come into play. They keep the wrist pin from contacting the cylinder wall. Another way to keep the pin off the wall is to use Teflon wrist pin buttons that fit into the inside diameter of the wrist pin and stick out just far enough to ride on the cylinder wall, keeping the harder material of the wrist pin off the wall. The soft material won't score the wall, particularly while being bathed in engine oil that is splashed up off the crankshaft.
http://www.cbperformance.com/catalog.asp?ProductID=172

Resizing a rod is explained here....(taken from www.cdxetextbook.com)
Part 2: Step-by-step instruction

Remove piston pins
On these connecting rods the piston pins are semi-floating, which means they are free to move in the piston, but they are pinched into a permanent position in the small end of the rod.
To remove a pressed-in pin, the piston is set in a hydraulic press which forces the pin out of the grip of the small end of the rod.
Remove rod caps and bolts
With the rods separated, the caps now need to be removed. It is important that if you need to hit these to separate them, you only do this with a brass hammer.
Next, the old bolts are pushed out of the rod with the hydraulic press, and discarded.
Grind rod ends and caps
Each cap is kept with its rod and, one by one, their ends are very slightly reground in the same manner the main caps of the block were.
After the caps are done, the ends of the rods themselves are ground down a little as well. The grinding leaves a sharp edge that will have a tendency to scrape the backs of the rod bearings when they are installed, so the edges are smoothed with a file.
Install new rod bolts
Depending on the type of new rod bolts to be installed, the edge of the bolt hole may need to be chamfered to accept its shape.
Any metal shavings are cleaned out of the rods and caps and the bolt holes are cleared to prepare them for the new bolts.
Connecting rod bolts live deep in the motor and take a lot of abuse, so it is strongly recommended that - here in particular - you fit the highest quality bolts that you can get.
The threads are lubricated and the nuts installed and torqued on each rod. With brand new bolts the nuts are tightened and torqued and then loosened again and tightened and torqued again a total of three times. This will break in the bolt and make sure that the proper stretch is achieved for all of the bolts before the rod big ends are resized.
Realign connecting rod big ends
One by one each rod is honed to return the big end back to a perfect circle. The size is checked frequently during the process and when they are close to specification, they are left to cool for a while. Just as when the block was honed to realign it, the metal expands from the heat of the friction of the honing stones. Once cooled, the job is finished and the rods will all be within tolerance of the correct specification.
Larger machine shops might have a rod production machine. It can be set up to run off large numbers of rods in a short period of time. So, instead of waiting for your rods to be machined, sometimes it makes more sense to buy a whole set, with high quality new bolts already installed.