Hot Rods Old connecting rod balance from factory

I know that some people sometimes think that the old stuff might not be as good as modern times,,,and sometimes they are correct.
I recently cleaned and checked my rods and was amazed at how close they all were.
They were cleaned in Berrymans Chemdip,,,,it works great to get all the old varnish off and only have bare metal showing.

Anyway,,,,these rods are from a 1955 Desoto 291.
I was dumbfounded as to how accurate they all were from the factory.
I wrote the readings down on paper and you can see the pics.
Small end within about 2 grams total.
Big end all within 3 grams,,,except number 6,,,it was about 16 grams different.
The balance pad on that one was about .025 “shorter than the rest.
Other than that,,,they were almost identical,,,,and all coming from back in the day,,,and being done on a production line.

I have weighed modern rods from engines,,,and many are off by 20 to30 grams,,,,about 5 out of 8 usually.
How did they do all of this so accurately,,,,just taking more pride,,,or just using good equipment even back then ?

Tommy

 

Oh yeah,,,here are some pics of one of the rods laying next to it’s big cousin 426!
They are even machined the same way around the pin boss,,,and the beam is forged the same shape.
I guess if it isn’t broke,,,don’t fix it,,,Lol.

Tommy

 

cool thanks for posting.

 

Nice. I had a '40 Plymouth business coupe with the 291 hemi. Ran smooth.

 

I love shit like that. Thanks for posting. Always impressed how those guys were able to hold that kind of precision and consistency back then with the tools available.

Rotating assemblies of any kind, can usually be improved a fair bit. Driveshafts, wheel/tires etc etc.. There's "balanced" or technically within spec, and then, there's balanced. Even a lawn mower benefits noticeably from careful track and balance of the blade. Smoother running less vibration, higher RPM = more power. Tolerance "stack ups" can be a funny thing.

 

That's really cool. Thanks for sharing.

 

The first engine I ever worked on was an early Cadillac, then later a Desoto Hemi.
I was pretty shocked later with small block Fords and Chevies to see rough cast combustion chambers and the like. how could you have consistent compression ratios with unmachined combustion chambers?

Those early hemis are really well made, with forged crankshafts, exhaust valve hard insert seats, and of course the fantastic dome combustion chambers.

 

I've found some reading on Ford balancing during Model A and earliest V8 production and in For's own engine rebuilding program. An interesting feature was the general use of selection as the lead-in for balancing and fitting... large numbers of rods, pistons, pins etc. were carefully sorted by weight, length, diameters, etc.
Longest pins went into pistons with high pin holes, also all sorted by weight, pins had been sorted into high-low-perfect-scrap diameters first...everything that moved was closely sorted. Thinking about how they coordinated all that without computers just gave me a headache.