Balancing the pistons of the Model A Ford

[SSsssteamer]

A year ago I balanced my model A engine's pistons and my connecting rods as shown in the following video. I am totally amazed about how much smoother my '31 model A engine now runs after being balanced this way. I bought my scale at a garage sale for $2. See the how to video at: http://automoto101.com/piston-balanc...m_medium=Trust

My final weigh in was done with comparing the piston assemblies with each other.

[kenparker]

I did that with the engine that is now on the engine test run stand. It has countr balsnced crank, and lightened fly wheel and v8 PP. The crank and flywheel and clutch were balanced by pro with high dollar equipment. The rods and pistons were balanced by me just like the video above. Rods and pistons were balanced to within 1/4 gram. On the engine stand it is one smoooooooooooooooth running engine. Today project is to change th distributor from a stock dizzy to a FS electronic. Then we will see again how smooth it is. Final step will be to put a downdraft carb on it before install in 'le coupe.

Have not decided whether to use a Stromberg 97 or get on of those Webers. ken

[Kevin in NJ]

It nice to hear people having great results from careful work!!

Imagine what a factory engine was like.

There the rods would be +-1g at each end. When matched with pistons the whole units would be within 4 grams of each other in an engine. Coupled with tightly balanced crank and a well centered and balanced flywheel.

I mention this because I think it is pretty rare to get all the parts to the level the factory would have had the balance and machining precision. The more I learn the more I find Ford, during production, maintained some pretty high standards for precision work in high volume. It is difficult to get the same level of precision without some very special setups.

That being said, there are clearly people getting pretty darn close. The more we try the bettter we get.

[Colonel Biggs]

Where did you do the balancing on the connecting rods?

Gordon
Houston

[BillLee/Chandler, TX]

A couple of questions regarding what I saw on the video:

1. When is "close" == "good enough"? The video started out with a max variance in pistons of 1.2 gms and .2 gms for the wrist pins. For that example, we're talking about .3% Seems that a gram difference for a 330 gm piston should be "good enough".

2. Why do the pistons and wrist pins separately? Since the video is very specific about not mixing them up, it seems to me that since they are a unit when delivered and will always be a unit forever, that the total weight of the piston and wrist pin needs to be balanced, not necessarily each individual piece.

Not trying to contradict what has been said, just trying to understand.

[kenparker]

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Bill, maybe we need to do some piston weighing tomorrow. juz fer fun. If close enough is good enough, but you have the equipment and are capable to get within 1/4 gram, why not do your best. Less than your very best is not good enough to me. ken

btw I weighed the pins separately just ot getthe measure/weight, then put them together and final weigh was with piston, pin and keepers.

Colonel, I will get pictures and be back tomorrow. ken

[H. L. Chauvin]

Hi Steamer,

Thanks, and in my opinion, if every professional mechanic and/or every shade tree mechanic, and/or every Model A owner in the past 60 years would have considered:

1. Carefully trying to obtain Model A mechanical precision in lieu of employing the very normal "good enough for a Model A" technology that existed back then; and,

2. Adhering strictly to proper Ford recommended Model A maintenance,

many of these tough Model A's that went to the junk yard would still be here among today.

Trying to achieve Model A mechanical precision & excellence, and generally trying to do it all right, always pays off in the long run not to constantly be wasting valuable time and money on constant Model A rebuilding and repairs.

[kenparker]

Said I would be back tomorrow. Well, my Falcons are winning and the game got boring, so out to the shop to take pictures.

Four pictures showing weighing the big end, the little end and closeups of the bearing supports for the two ends. Keep in mind. 1. the shaft of the rod should be parellell to the weighing scale. 2. each end should have some type of support to minimize the friction of the supports and the scale itself - especialy the big end. In this case small bearings. 3. the weighing spot on the scale should be in the same spot each time.

it wont let me add photos. find out problem and load photos later. ken

[kenparker]

this little laptop gives me more grief than all the Model A's I have put together.
Finally here are the pictures I promised. ken

[BillLee/Chandler, TX]

RE: "good enough".....

What were the Ford specs for piston weight and variance within an engine?

[Tom Wesenberg]

Originally Posted by BillLee/Chandler, TX

RE: "good enough".....

What were the Ford specs for piston weight and variance within an engine?

See Kevin in #3.

[daveymc29]

I watched the video and didn't see how the weight of the rods is reduced (or added)
I heard of an engine builder that welded to the rod to add enough weight that he could get a set that were quite close. Several of his engines had rods go through the block.It seems to me that welding on a rod would change the molecular structure and render it prone to cracking and failure. Any thoughts on both taking weight of or adding weight?

[H. L. Chauvin]

Posted this once before, (and maybe some may consider this overkill), but after Mr. Ron Kelley balanced my counter-weighted crank with new crank gear, lightened flywheel with new ring gear, etc., etc., I went for .5 grams between overall weight differences of rods & pistons with rings installed.

There always was, without a doubt, a very definite reason as to why the Hamilton & Ball Railroad Pocket Watches were superior to and far outlasted the cheap $1.00 Waterbury pocket watches; and also there is definite a reason why Model A engine re-builders are busy dealing with the "good enough for a Model A" type of mechanics.

[Mike V. Florida]

Originally Posted by SSsssteamer

I am totally amazed about how much smoother my '31 model A engine now runs after being balanced this way.

Ever wonder how many other systems the owner would be amazed with if they took the care with those as you did with yours?

[SSsssteamer]

Originally Posted by Colonel Biggs

Where did you do the balancing on the connecting rods?

Gordon
Houston

On my connecting rods, I had three rods that were near spot on. I ground a little metal off of two of the rods. I had one rod that was way too light. I machined two flat washers that I installed under the connection rod cap's nuts. After some grinding on those flat washers, it was the same exact weight as the other three rods. I did not know about weighing both ends of the rods separately as done in the Ken Parker's reply. The way that I did it, it worked well for me this time with no rear view mirror vibration in the end. I will try Ken's way next time. In the end, the total weight of the piston/rod assemblies were all equal within 0.1 ounce of each other's piston/rod assembly's total weight. My (postal?) scale measures up to 80 ounces in 0.1 ounce increments. 2.9 grams = 0.1 ounces

[BillLee/Chandler, TX]

Originally Posted by Tom Wesenberg

See Kevin in #3.

O.k., missed that.

So.... fixing a 1.2 gm variance on our Model A pistons COULD be classified as OCD?

[Tom Wesenberg]

Originally Posted by BillLee/Chandler, TX

O.k., missed that.

So.... fixing a 1.2 gm variance on our Model A pistons COULD be classified as OCD?

I have two precision scales and will be balancing my pistons and rods when the time comes. It looked like the one ebay sale wasn't going to happen, so I bid on the second one. Of course, then you wind up with two, so one needs to be sold.

[Dodge]

Having the pistons and rods balanced is the most important part of the balance job.
Get them as close as possible.

[Colonel Biggs]

Sir Kenneth --

That's one fancy balancing rig! When you are "adjusting" the weights of the rods, are you using small drill bits -- as in the piston balancing video? If so, can this require several drill spots, or are the rods pretty closely balanced in general?

What is the reasoning for not just balancing the rod as a single entity, and making the drill spot in the center of the rod?

[H. L. Chauvin]

FWIW:

For those who may remember Mr. Ron Cloat, (Rainmaker Ron),and his Model A parts supply shop, I ordered his advertised new Model A pistons and new Model A ring set.

After placing each individual piston on my new gram scale, all four (4) pistons weighed exactly the same; and after after placing each individual ring set on my new gram scale, all four (4) ring sets weighed exactly the same.

If one weighs old former connecting rod castle nuts, and/or new castle nuts from different Model A parts suppliers, and some from Non-Model A parts suppliers, one quickly finds that castle nut can vary in weight.

Next, if one orders thin washers, (not lock washers), from different suppliers and manufacturers, one finds their weights are different.

Between swapping castle nuts and adding and removing washers, one can come very close to attaining the same weight of the connecting rods on the Babbitt end.