Balancing an engine

[Rich P. Bingham]

Refurbishing the engine for my '13. By matching heavier pistons with lighter connecting rods, weights vary 9/10 of an ounce, 1/2 oz., and 3/10 oz. over the lightest pairing. I suppose it's possible to have them weigh up equal, how necessary is that ? What do experienced T engine rebuilders consider to be an acceptable difference ? Running cast iron pistons if that makes a difference.

[Dan Hatch]

Balance pistons with pins. Then balance rods. Use grams, not oz.
Also look on YouTube about balancing rods. You just don’t throw them on a scale. Dan

[Henry K. Lee]

To add to Dan's comments..., proper balancing of an engine is a lot of work but pays off by longevity and reliability. Static balancing vs dynamic balancing with bob weighting and surface honing. How far do you want this thread to go?

Just Sayin'

Hank

[ChrisB]

Here are a few links on balancing from old forum posts.

Lots of information in here (ignore the insults). Make sure you read the parts on bent rods.

https://www.mtfca.com/discus/messages/3 ... 1376421364

https://www.mtfca.com/discus/messages/1 ... 1319779403

https://www.mtfca.com/discus/messages/3 ... 1364075689

https://www.mtfca.com/discus/messages/7 ... 1495042336

https://www.mtfca.com/discus/messages/2 ... 1331940062

[Rich P. Bingham]

Thank you Chris, the links are very helpful

[Gen3AntiqueAuto]

Hire someone and watch them do it. Grams - tenths of grams - you have to hold your breath or the weight changes tenths of grams. My balance guy (now gone) used to spin the parts on a computer thing (see video link below).

I'm currently looking for a new machine shop that can also computer balance the internals near me in MA.

Here's one being balanced:
https://youtu.be/8W0G1vEHqrc

[J and M Machine]

Refurbishing the engine for my '13. By matching heavier pistons with lighter connecting rods, weights vary 9/10 of an ounce, 1/2 oz., and 3/10 oz. over the lightest pairing. I suppose it's possible to have them weigh up equal, how necessary is that ? What do experienced T engine rebuilders consider to be an acceptable difference ? Running cast iron pistons if that makes a difference.

It's important if you want the engine to run smoothly and biggest improvement you can make is balancing the flywheel.
The rods have to be weighed end to end to find lightest then all others should be made to weigh same amount.
Same goes for total weight of rod and piston weights. It will be big improvement on how engine runs.
Doesn't make a difference regarding balance if they are cast iron or aluminum, in aspect to balance them.

You can see in pictures what it takes to do the pistons and crank and flywheel.
From previous posts others have posted from past you cans see how we did rods.
As I 've mentioned it makes a big difference in how the engines run.
These engines were built with a designed tolerance of balance ;however 100 years later and how many mismatched parts/rebuilds later have caused them to run poorly.

Unless you think; "It's only a Model T"

[speedytinc]

Dont forget the transmission drums individually, output plate & clutch hub. Also the triple gears.
All these pieces are off, some way off. Drums are cast & machined. Most have a thick/heavy side & a thin/light side.
Taking the time to do a full balance will allow the motor to run more smoothly @ hi speed & more effortlessly @ low speeds.

[TXGOAT2]

It takes power to shake, and the power has to come from the engine. Shaking adds needless bearing loads and friction. Shaking also works to loosen up the entire car and promotes sheet metal cracking, loose bolts, loose wood joints, door hinge wear, etc. Balancing an engine reduces all these negative effects. Adding a counterbalanced crankshaft and balancing all rotating parts might free up 4 or 5 horsepower in an otherwise stock engine/transmission. Balancing improves power, speed, and economy and makes driving pleasanter.