Connecting rod reconditioning procedure

[cgarb]

I do know that bearings are not round, but i did not realize that having a bore that is not round would be acceptable. I wasnt sure how that would effect the crush the bearing has built into it.

[PackardV8]

I do know that bearings are not round, but i did not realize that having a bore that is not round would be acceptable. I wasnt sure how that would effect the crush the bearing has built into it.

Most older two-piece reconned OEM rods aren't round. The Clevite book shows this clearly in a diagram and says, in effect, just measure 6-12 o'clock and don't worry about the parting line.

We have a power stroke machine with a diamond head which will clean up rods four at a time and zip-pop. However, the diamonds leave a very distinct indication of the out-of-round at the parting lines. The Sunnen hone with vitreous stones leaves a much less visible indication, but measures the same.

Interestingly, the current tech cracked cap rods are round.

[KnightEngines]

Something a lot of shops miss - heat changes size more than you think.
I keep a bucket of soapy water at room temp next to my rod hone, after honing I dump the rods in it to normalise their temps & check when they're all at the same temp then tweak from there.

[modok]

The wisdom I was taught is "if you can cover it with your thumb, it isn't there."
1/2" inch on either side of the parting can be ignored, perhaps more depending.

I still want the overall average size to below the high limit, so I know there is enough crush.

[BCjohnny]

Interestingly, the current tech cracked cap rods are round

Round holes are cheap ...... the rod is made in one and then fractured with no subsequent machining

Sintered ones are relatively easy to crack the cap off, but even forged ones go (without chill) with enough of an initiation notch, hence the 'deep' forged in relief at the parting line of many diesel rods

Whatever the claimed engineering benefits of a 'cracked cap' rod, it mostly about cost, as always ......

[Baprace]

I dont need to take .005 to get the mating faces clean, im taking the extra material to attempt to get a bore that is round. I took .002 first and when you measured the bore was after the bolts were torqued they were still not cleaned up in the bore near the splits.

I find that ford oem rods are the worst to grind the mating surfaces and keep the parting measurements tight / on size for a round measurement , I will cut one side at a time trying to follow the original angle cut to keep the part line size tighter , some part line shadows / that will not clean compleatly is acceptable to me , 320* degree of correct size is ok with me , part line size issue , I can't help without way over cutting the part line surface.

[Mummert]

I've resized more 302 rods with ARP bolts than most in my younger days. Checking the way the rods come apart with the Oem bolts is the first place to start, if even one of the caps don't slide over the threads of the bolts perfectly, throw the whole set in the trash, 302 rods are cheap. The rods that have D1OE on the caps are good for the street use and thats about it. Unfortunatley they comprise 85% of the 302 rods made, 68-70 and 92 and later have the bridged caps, much better.

Most of the problem with aftermarket bolts(already been mentioned) is not having the correct chamfer under the bolt head or the bolt head hitting in the radius of the broach making it seat poorly. It can be a little tough because the bolt hole sits very close to the broach line. Its very common to see them fall out at the parting line. With good prep you can hold to a minimum. The caps need to to slide over the bolt threads with no dragging, just like an OEM rod that has never got hot. They should get snug right when they hit the registers, it should take a slight tap from a hammer to get them seat.
After rod cutting you should check the mating surfaces on a precision sanding block. Unless you sharpen the stone frequently it gets glazed and will cut a rainbow, the bigger cuts you take the worse it gets . Having some fall out at the parting line isn't uncommon on 302 stuff. If you can hold dimension within a 1/4" of the parting line your doing good. The fall out at the parting line helps keep the D10E rods alive when the caps distort and the start sucking the sides in and try to grab the rod bearing.

For your future builds if you are using rods that have D10E on the caps don't put bolts in them its a waste of time, the area between the nut and the balance pad will distort when abused. Those rods and the stock bolts work good for 325hp and 6000rpm on the street.

[cgarb]

Thank you all for the advise. I will more closely inspect the rods before I just knock all the bolts out next time. I was cutting C3 casting rods. The cap looks considerably stronger than the 302 rods the engine had.

[novafornow]

I have a question regarding this topic. How out of round would one set as the point that you must do something? If freshening an engine that does not see a ton of abuse, what is acceptable? 0.0002"? 0.0005"? On my personal SBC, It looked to be about 0.0002" and I went ahead and ran it with new bearings. No trouble, but have been wondering what one that does this day in and day out would consider acceptable.

[BCjohnny]

Used rods that are two tenths out are to all intents and purposes 'round' .....

Five tenths would be just acceptable, as long as the parting line isn't pinching in too much, and you've the correct clearance on the journal ..... but I'd personally consider resizing at that

On anything worthwhile I pre-stress the rods across the parting line, for obvious reasons ...... added benefit is they mostly 'clean up' with that

[novafornow]

Thanks for the reply.

[MotionMachine]

As everyone knows, it's a constant fight to keep rods from going either barrel or hourglass using CR mandrels on a manual machine. If the rods are round but still have a couple of tenths taper when it's close to finish size, I'll finish the them with a PL mandrel using a finish stone. It'll take the taper right out and leave a much better finish. But if the rods aren't round, it won't correct that and will actually make it worse, being a one stone mandrel.