rebuilt connecting rod
 

What is done to the crank end of the rod when it is rebuilt ?

kurt

Re: rebuilt connecting rod
 

They shorten the cap slightly and rebore it so it is perfectly round again, a good shop will also check it for twist in the I beam and true it as needed. Tim

Re: rebuilt connecting rod
 

Tim, when rod is rebored is just the cap cut and not the rod or it would have two different length bearing shells ? it seems to me.

kurt

Re: rebuilt connecting rod
 

Cut just the cap. Very little is taken off.

Re: rebuilt connecting rod
 

Depending on the rod, in many OHV situations the rod-bolts are replaced before the bore/hone operation on the big end.

Re: rebuilt connecting rod
 

Hi kurt


Since flathead rods have captive bolts only the cap is cut. After boring/honing to the correct size again, one bearing shell may be above the parting line and the other shell below, but it doesn't hurt a thing. The parting lines on many rod and main caps aren't exactly centered from the factory either.

Re: rebuilt connecting rod
 

Also, consider that our flathead rods (prior to 1949) used full-floater bearings, so one doesn't think about a bearing edge being above/below a parting line as the whole bearing rotates/floats in the rod bore and there is no "tang" to hold it in place.

Re: rebuilt connecting rod
 

When I had the 8ba for my '39 p/u rebuilt I asked the machinist about reconditioning the rods. He said the process wasn't like say a SBC but it could be done. At the time NOS French rods were available from SoCal Speed for not much more than the cost of reconditioning my old rods.

Re: rebuilt connecting rod
 

Back in the day, we didn't recondition rods. We checked 'em out, and if they looked OK, we got a set of .002" under rod bearings.

Re: rebuilt connecting rod
 

And there were probably 2 reasons he said that:

1) Flathead rods have bushings that are swedged in and burnished/honed. Most stock SBC type rods don't have wristpin bushings. However, most aftermarket performance rods do.

2) Flathead rods don't have balance pads, so the correct procedure to balance the big ends requires using a lathe to remove material from the sides of the rod caps (above the polished areas). One has to make a special fixture to do this (which I've done).

Re: rebuilt connecting rod
 

What do you do to balance the pin bushed end of the rod? How did Ford do it?

Re: rebuilt connecting rod
 

There usually isn't as much to worry about (as far as metal removal). What Ford did is they turned both sides of the bushing area of the rod. If you inspect a few, you'll see that they removed a little material from certain rods. I don't try to do that as my little lathe doesn't have enough swing for the rod. If I had a bigger lathe, I'd make a fixture plate so I could do it like Ford did.

I just take the ends to a belt sander - and sometimes a bit to the upper beams. As you might know, you have to balance each end of the rod separately. And also get to the final weight being the same.

Hmmmm . . . I guess I could make a fixture plate for my rotary table and do it on a mill? That gives me a new idea! (Like I need any more damn flathead specific projects!). LOL

Re: rebuilt connecting rod
 

Here is how I do the big end: You'll see the fixture that I use and an example of one that is done. I'll also show what most shops do - which is grind the strength beams on the bottom (I think that is totally wrong!).

My process (same as Ford did it):

Attachment 562329

Attachment 562330

Attachment 562331

How I've seen all the shops do it - notice the grinding on the cap strengthening beams:

Attachment 562332