MTFCA Forum

What do you all think about crankshaft counterweights?
Are they easier on your eingine by elemenating some vibration, or to they put too much weight on the shaft? I will be curious to see what you all think!

Counterweights are a very good idea. They do add rotating mass, but the improved balance and reduced vibration offset any power loss. Personally, I would not attempt to add counterweights to an original crankshaft. There are a number of pitfalls to doing that, and besides, the orignal shaft may have issues related to age and long use. Good original shafts get scarcer by the day, too. I would put my money into a new Scat counterbalanced crank and rod set. Getting rid of a substantial portion of the engine vibration saves wear and tear on the entire vehicle. If you want a fast T, better plan on getting the engine, transmission, and entire driveline in good shape. If you want a reliable T, the same applies.

I had two engines that had been rebuilt from known engine builder and the customer did not like the vibration they had at higher RPM's I tore the first one down and it had the Dunn counter weights on it. I do not know if these where originals or the repops. I first sent the crank and flywheel out for dynamic balancing, reassembled and vibration was still there. I removed the weights, had it rebalanced and vibration was gone? Did the same to the second engine and customer was happy! I do not know if the weights are better to use with the iron pistons or the aluminum ones some people swear by them and some swear at them. So this is my experiance with them, I have some on the shelf if any one wants them! Hope this helps.

A problem I saw in an engine I rebuilt which was equipped with Dunn counter weights was a deflection of the crankshaft. The weights appeared to be balanced but the crankshaft had a pretty serious bow whe checked on V blocks. Don't remember if the mains were affected but I had new babbitt poured in the block for other reasons.

Alitle confused, why would it be bad on an original crankshaft?

They wouldn't be bad at all, IF they were PROPERLY INSTALLED on a GOOD crankshaft and the entire crank, rods, and pistons assembly adjusted and balanced as needed. That's saying a lot. For detailed information, enter; "Dunn Counterweights" in the search box at the top right of this page. This lengthy 2005 discussion by several expert and experienced people also includes some very good photos of Dunn weights installed on a T crankshaft.

Forum contributor and noted engine builder, Henry "Hank" Lee has used them on at least one engine that he had for sale in the classifies, so they can't be all that bad. As others have stated, a total balance of the rotating components is necessary and the crank should be an EE crank and checked for cracks and straightness before adding anything to it.

ModelTWoods wrote: ↑

Fri Sep 03, 2021 1:08 pm

Forum contributor and noted engine builder, Henry "Hank" Lee has used them on at least one engine that he had for sale in the classifies, so they can't be all that bad. As others have stated, a total balance of the rotating components is necessary and the crank should be an EE crank and checked for cracks and straightness before adding anything to it.

Dunn counter weights were designed/cast for earlier diamond type cranks. The castings capture the diamond.
They wont secure to the later cranks without serious machining & an anchoring method. Either way, its not a bolt & go.
As I mentioned in the earlier post. Done it, ran it, liked it.

What is the different crank years?

I think 24 went away from the diamond to the heavier straight throws.
The EE's are 27 (scarce, late version with better metallurgy)

I have a 26 eingine, does that mean that they would not fit?

Not without modification, assuming thats the original crank.

The 1924/25 AA crank is still a desirable crank, from memory the metallurgy is not that different from the 26/7 EE, have the break down on test some place in my notes, will try and find later. The %'s are similar but the AA had about 1% Chromium in it. I have come across a broken EE once in a stationary T engine.

Jonah

If lucky, if your T is a late '27 then it will have this crankshaft with straight side throws, and be marked "EE". These are the most desired original Model T crankshafts. The Dunn weights won't bolt on easy, as the cast weights have narrowed section to mate to the pointy diamond shape throw of the earlier crankshafts.

The Dunn bolt on two piece counter weights made today are $150/set reproductions of the early Dunn pieces, those were made and fit only to the earlier crankshafts with the 'diamond' pointy shape on the sides of the throws. The catalogs of these new parts state that fact.

My eingine is a November 26 as marked on blocks and car was around then too being a wooden wheeled.

Still confused on the diamond thing though

Of the 2 pix, the 2nd is the diamond crank. The center of the throw is wider than @ the rod or crank throw ends. Narrower also.
The first crank is the late style. The throw sides are parallel & heavier.

Jonah,

They're not the best photographs to demonstrate the cranks differences. No doubt someone will come along with a broken piece that'll better show what they look like, but for the moment I've drawn a section of what the web (or 'throw') would look like for each crank if you were to cut through it.

This is clearly not to scale, and I've exaggerated the shape of the 'diamond' crank a little, but hopefully it'll make sense?

From Bruce's encyclopedia

"from 1909 until about 1924 the crankshafts were made of Vanadium steel. These seemed to have the diamond-shaped throws between the connecting rod bearings.
About 1924 the material was changed to a heat- treated type and the throws became more rectangular in shape. These were imprinted with “AA” on one of the throws.
In 1927 the material was again changed and was identified by an “EE” on the throws. This final type is believed to the best of the cranks."

Generally the date of change to the 'EE" material happened after July 1926, with the start of 14,000,000 engine serial #s.

Great information Dan, clarified a lot for me.
What is the general opinion of the AA crank ?
Is it desirable too and are the weights as difficult as the EE to get right ?

If you want a counterweighted crank, pony up and buy a Scat. I have put in a couple dozen of them. The bolt on weights can work if carefully installed on the diamond web cranks and run very smooth until they come loose which they will in time. The vintage Sure Mike cranks also run well until they break. I have repaired many engines that were destroyed by this stuff. If your budget doesn’t justify a Scat crank, at least get your T crank magnafluxed so you know it will last. I will mag any crank for free if you just get it here. Transmission drums, blocks, and heads too. I have magged and reground stock T cranks available here. I just got a run of 20 of them back from my crank grinder guy. They may be the last because he is going to retire and it is getting near impossible to find good cores to regrind. I only send him the late crank forgings. No diamond web stuff. EE cranks are the best but they are hard to come up with. While being tougher and more resistant to breaking, the steel formula is softer than the AA cranks and many of them are worn beyond regrinding.

Erik, last I heard, he didn't have enough money to even take care of an aging overheating radiator, much less buy an expensive Scat Crank, altho I agree, it's a good option. Seems from previous posts re Rockies for the car, radiator issues, now wanting to balance a crank, I'm thinking he's got too many irons in the fire. I think getting the radiator to cool the engine properly should be his first, if not only, priority at the moment. JMHO.

Erik, what does Magnaflux mean?

I'd suggest the OP get the basic systems working first, then go over the entire car looking for loose screws and bolts, cracks, loose rivets, and so forth. Loose fasteners anywhere on the car, but especially things like motor mounts, can cause excess noise and vibration. I'd also want tp lubricate every moving part on the car, including every chassis lube point and every other moving part of the car, not forgetting the springs and things like door latches and hinges. The wiring probably needs a good going over, too. A lot can be done to a car to improve its operation by investigating it and spending time and just a little money. I'd get a Ford repair manual and read it, and refer to it as needed. Model Ts have a lot of wear points that can be adjusted and many items that need regular oiling or greasing. Spending time rather than money can often be very rewarding, especially on a 100 year old car that has been sitting. This forum is a very good source of T-specific information that is available any time. Most vehicles do not have a source of support like this.

Magnaflux is a process by which hidden cracks in metal parts can be detected.

Jonah, magnaflux is basically a method of "Xraying" the metal for hidden cracks, using a chemical and special light.