Balancing Model A Rods
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Balancing Model A Rods
After having rods poured and machined customer decided to have me balance the rotating assembly on a stock model A engine. Three of the rods were within range to balance normally, but one the big end was 25 grams light. No way could I take that much metal from the heavy three. So I made two new rod nuts from mallory metal. They were 12 grams heavier each ! This made it so I could balance them the normal way. The second picture is balancing the rods in a lathe the right way. The mandrel is made of nylon to protect the babbit
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You are only limited by your machinery and your imagination!
Re: Balancing Model A Rods
While tightening them up, will you be lining up the slot in the nut with the hole in the bolt to slide the cotter pin in ?
I have tried searching for a weight comparison list of 12point nuts vs hexagonal to no avail to add to this reply. The 12point nut is drastically lighter, but 12 grams is a lot.
Cool project.
I have tried searching for a weight comparison list of 12point nuts vs hexagonal to no avail to add to this reply. The 12point nut is drastically lighter, but 12 grams is a lot.
Cool project.
Magnús Aðalvíkingur Finnbjörnsson
Re: Balancing Model A Rods
I had to add 12 grams each = 24 total. Yes you torque to 40 foot lbs, then tighten up to align the cotter pin up.
You are only limited by your machinery and your imagination!
- Dave Koehler
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Re: Balancing Model A Rods
I cringe any time the old fords, including the flathead v8 show up after 47 different rebuilds over the last 100+ years.
The rods often have unnecessarily long threads extending out beyond the nut. I have trimmed some of them down when it was possible.
The HM rod nut is a great idea. I will have to try that when the time comes.
The rods often have unnecessarily long threads extending out beyond the nut. I have trimmed some of them down when it was possible.
The HM rod nut is a great idea. I will have to try that when the time comes.
Dave Koehler - Koehler Injection
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
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"Never let a race car know that you are in a hurry."
Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software
http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
Re: Balancing Model A Rods
Hmmm - long threads and additional weight needed. How about a case-hardened coupling nut?Dave Koehler wrote: ↑Mon Nov 29, 2021 9:11 am The rods often have unnecessarily long threads extending out beyond the nut.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
Re: Balancing Model A Rods
The long nut would work for weight. but I need the castle for use with a cotter pin
You are only limited by your machinery and your imagination!
Re: Balancing Model A Rods
Only if the guy is a stickler for authenticity in a part no one will ever see.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
Re: Balancing Model A Rods
I have always used the cotter pins on the Model A rods. With only 40lbs of torque on a 7/16 bolt I was afraid the stretch on the bolt was not enough to keep it from loosing. No way to measure the stretch on these rods.
You are only limited by your machinery and your imagination!
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Re: Balancing Model A Rods
If only one rod was out, why not just find another rod?
Helping to Deliver the Promise of Flying Cars
Re: Balancing Model A Rods
OEM Ford A rods have poured babbit bearings. Today, just finding the guy to pour and machine a new one is not easy. My guy is backed up months.SchmidtMotorWorks wrote: ↑Sat Dec 04, 2021 12:32 pm If only one rod was out, why not just find another rod?
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
Re: Balancing Model A Rods
This customer had the crank ground the minimum on the worst journal and the other three ground to the same size. Then the babbit in the rods bored to size w shims for the right clearance. This makes replacement of the rod a custom piece.
You are only limited by your machinery and your imagination!
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Re: Balancing Model A Rods
Interesting, I wonder how much of the 25gs came off the rod pin.
Maybe it it were spun up with bws, it would have been close.
Helping to Deliver the Promise of Flying Cars
Re: Balancing Model A Rods
Remember a 4 cylinder crank is a flat plane crank. The crank is balanced neutral without any bob weights. Then the rods and pistons are balance to be a matched set. This means that changing the weight of the rods and pistons has no bearing on the balance of the crankshaft. PS: the rod journals are all the same size, just not a normal .010 - .020 - .030 undersized
You are only limited by your machinery and your imagination!
Re: Balancing Model A Rods
SchmidtMotorWorks
I just realized what the bws stood for bobweights ! And if the journals were different sizes you are right. But note they finished all the same size.
I just realized what the bws stood for bobweights ! And if the journals were different sizes you are right. But note they finished all the same size.
You are only limited by your machinery and your imagination!