Engine Balancing - Tech - How To - Terminology - Circle Track Magazine

How To Balance An Engine - Engine-Balancing Basics - Car Craft Magazine

You can balance it, but you are really just picking the rpm band you don't want vibration in.

There's also another factor - windage from oil. Smokey Yunick spent some time in the 1960's getting high speed photography of a working crankshaft. In his book, Power Secrets, he publishes one of those photos. It shows a crank at high rpm with 3-4 quarts of oil wrapped on it.

We spend a lot of money to get things within a quarter gram, but then even a quart of oil will throw it completely off. It's exactly why racers use scrapers, windage trays, and have 7 quart pans, to make up for the loss of oil that sticks to the crank. Another more modern technique is to use oil resistant coatings on the lower rods, crankshaft cheeks, etc. to make it let go and reduce it.

I've asked a lot of guys who race, and machinists who make race engines, they all agree, balancing and the expense is largely something street car guys think they need. It's not that critical. What's 3% of a 1600 gram bob weight? 48 grams. Plus some fraction of a quart of oil, which weighs 800 grams. For some portion of weight that takes it out of balance, you have another that puts it back in, the whole thing is a spinning mass of changing volume dependent on rpm.

Again, production tolerances on factory parts do well enough. There's plenty of other sources of vibration, the primary and secondary nodes even caused engine designers to add shafts to four cylinders so the driver wouldn't feel them. Those don't stop the engine from having vibration, they just add counter vibration. It's still doing it at the journal level - the block is pushed back at the same time to offset it, adding even more force on the oil wedge.

If the engine is internally balanced, add a neutral harmonic and flywheel, consider it done. With hard motor mounts, the primary and secondary vibrations could likely be felt anyway.

The racer guys don't worry about alittle vibes.... the motor is going to come apart after the race anyway. Perfect may be impossible, but, I have personally taken apart balanced an put back together more than a few motors that were cracking bellhousings, and just not performing right. This thread was started because his crank broke, it would suck to have that happen again......

EXCUSE ME BIGTIME---------------------

I don't know where some of you come up with this stuff about balance doesn't matter----------maybe if you are rebuilding an oem engine with a matched set of stock replacement type pistons and it never goes above 3000-3500------------But if you are building an engine(and I don't mean assembling parts bought from Summit,Jegs,E-bay,etc) with stroker cranks, billet rods, custom pistons, etc you will need to balance it and all the rotating pieces----------

I have two machines in my shop that make power without buying any parts---the surface grinder and the balancer-----------

And I balance 2 or 3 engines per week -------------

Yes he does say "there is a tremendous amount of oil caught up in the windage from the spinning crank and wrapped around the crank throws" but when he says "wrapped around the crank throws" I doubt that he meant that 3-4 quarts was added to the rotating mass. Sure there is a significant oil mist in the crankcase, and that "oil cloud" movement is "totally random" (quoting Smokey). That oil cloud would be consuming a small amount of power by resisting the movement of the rotating/reciprocating assembly.
The oil cloud doesn't negate the positive effects of balancing.
Incidentally - a great book (Power Secrets).
Cheers,
Glen

I think you guys are getting wrapped around your own axle. Pay attention to Jerry he is telling it like it is.

Ed

Since you have already had one crankshaft failure, I would purchase all of related rotating parts from the same source as your new shortblock (flywheel, clutch kit, balancer, timing set) so that in the event of another engine failure, no blame could be put on you for installing the wrong, mis-balanced, damaged from previous engine failure.....ect. parts on this engine. You might even want to go as far as shipping them your heads & induction system, & have them send you back a complete assembled, balanced, & dyno tuned engine

The shortblock will come internally balanced. Any neutral balanced flywheel and Pressure Plate can be then fitted to the engine with nothing further to worry about.
I took the FW/PP assembly to a good tyre shop, where they did dynamically balance it an a Hofmann electronic wheel balancing machine.
The weight to be added was exactly the same I had added doing a static balancing,only about 10º off angle. So the static balancing was not that bad and is in any case better than nothing.
FW/PP is now balanced to within 3 gramm.
I will have to weld a metal plate with the correct weight to a lateral of the pressure plate. No way I am going to drill any holes in the PP nor the flywheel, which is aluminum and was neutral when I tested it separately.
My crankshat broke at the front, near the harmonic balancer, and despite that the original Ford balancer is sound, I will order the KC482 shortblock with a new harmonic balancer,, jut to make sure

My clutch is a McLeod product.On the clutch it says LuK.
LuK GmbH & Co. KG happens to be a German company of the SCHAEFFLER AUTOMOTIVE AFTERMARKET group. So this is a German clutch sold under the McLeod brand. I have seen many other clutches which look the same, so LuK clutches are selling under many different brands.
Interesting to see that not everything comes from China.

With an internally balanced rotating assembly, you will be OK with a clutch/ flywheel and a balancer with zero /neutral balance.

However, to be on the safe side- take the whole assembly for a check. My 2 cents...

As Rick, I did the flywheel in wheel balancing machine. However- I sent it to the engine shop who checked it. Not very expensive job. 200 euros is what I paid.

Good thing you're getting the engine back together, Eljaro.