Connecting rod balancing

[1crosscut]

I saw this video on Youtube about balancing connecting rods. It seems fairly straight forward how he does it. What say you??

https://www.youtube.com/watch?v=QLpiF0E0EJU

[Dodge]

Yeah that's how you do it.

[Kevin in NJ]

While I can not speak to how this guy is doing the balance, Yes you need to match the weights.

Ford factory during A production (as opposed to later replacement) would have the rod +-1 gram of a specified weight at each end. I have the print and that is what is called for in the print. Ford then matched sets of piston rods so they would be withing 4 grams total weight.

Getting the big end to be in good balance is very important for smooth running engine.

The balancing I researched weighed each end of the rod like this guy was doing the small end. He is making some assumptions about the center of the weight. Personally I would think the rotating end that connects to the crank would be the end that I would match, then do the whole rod matching on the small end. My guess is he does it this way cause the small end has less to take away.

That being said I am no expert on rod balancing. I just know other shops do each end on the scale.

[kenparker]

I went thru that process about two monts ago for a Model A engine. I balanced the small end to within 1/4 gram then balanced the large end to within 1/4 gram (full shim pack included).
Then weighed the complete rod. The combined weight of small end and large end are supposed to match the whole rod weight. If it did not I would have to do it again 'cause I had messed sumpin up.

Finally I weighed the complete assembly - piston and rod. Everything was matched to within 1 1/2 gram.

That is now one of the smoothest engine I have ever run. Counter balanced crank. Balanced rotating system. Overside - 1.73- Intake valves. slightly ported. Stipe 330 cam. Bored .060 over. Brumfield 5.9 head. Stock Zenith carb and FS distributor.

Still trying to get my Stromberg 48 to work, but I think I will have to give up on that one and go back to the Zenith.

Then the psitons, pins and rings and keepeers were weight matched to within 1/4 gram.

[d.j. moordigian]

Originally Posted by 1crosscut

I saw this video on Youtube about balancing connecting rods. It seems fairly straight forward how he does it. What say you??

https://www.youtube.com/watch?v=QLpiF0E0EJU

NO...
I do both ends,...because the beam could be heavy, somewhere in the center.
I also take weight off the big, when needed, off the weight pads,...I try to
stay away from the ribs on the cap if possible..

[George Miller]

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Originally Posted by kenparker

I went thru that process about two monts ago for a Model A engine. I balanced the small end to within 1/4 gram then balanced the large end to within 1/4 gram (full shim pack included).
Then weighed the complete rod. The combined weight of small end and large end are supposed to match the whole rod weight. If it did not I would have to do it again 'cause I had messed sumpin up.

Finally I weighed the complete assembly - piston and rod. Everything was matched to within 1 1/2 gram.

That is now one of the smoothest engine I have ever run. Counter balanced crank. Balanced rotating system. Overside - 1.73- Intake valves. slightly ported. Stipe 330 cam. Bored .060 over. Brumfield 5.9 head. Stock Zenith carb and FS distributor.

Still trying to get my Stromberg 48 to work, but I think I will have to give up on that one and go back to the Zenith.

Then the psitons, pins and rings and keepeers were weight matched to within 1/4 gram.

Try a B carb with a bored out intake to the same size as the B carb. You will feel the difference.

[rer_239]

i haven't checked the weight balance on my connecting rods yet, but the total rod weight is plus or minus 1.4 g. the utube videos i saw had areas on both ends that could be sanded down. but my A rods don't have such an obvious place to sand down. where do you guys do it?

[jhowes]

I have two questions on this. One is; what is a weight pad and the other is; :How did they do the crank, flywheel, and pressure plate before the digital machines were available. Factory technique? Jack

[Kurt in NJ]

The weight "pad" is different, the outside circumference of both big and little ends on both sides, Ford had a machine that weighed the shavings as it machined
The machines that balances the crankshaft, flywheel had a needle and a strobe light, the strobe showed position, the needle gave an idea of how much

[rer_239]

Okay thanks

[1crosscut]

Originally Posted by rer_239

i haven't checked the weight balance on my connecting rods yet, but the total rod weight is plus or minus 1.4 g. the utube videos i saw had areas on both ends that could be sanded down. but my A rods don't have such an obvious place to sand down. where do you guys do it?

Stay away from sanding. Too much of a possibility of getting fine grit into the babbit.
Use a sharp drill bit and take shallow evenly spaced cuts on the ends of the rods.
Picture is from Herm Kohnke.