motor balancing

im posting this in 2 forums, but each is for a different car, for a different reason. this is for my 73 cougar. im thinking about tearing the motor down have it cleaned, mic everything. < i told my friend this, and he told me about his pickup (pos 50's ford truck.... only a pos, cuz it needs body resto bad) it was his great grandparents truck, passed down in the family. well, back in the 60's you could send the motor off to be balanced by ford. they did, and the motor runs like new. i mean there are problems here and there, with gaskets, and seals like all motors, but no real wear. so this made me think about it. and ill leave it to you guys. should i have my 351 cleveland balanced? is it worth the cost?

Yes!

Okay. Balancing is the process by which all the internal MOVING parts are weight-matched to each other, and the crankshaft has weight added/subtracted at key areas, to "match" the weights being used. Virtually ALL "factory" engines since the 1910's have been "balanced".

The term "balanced" gets a lot of free press. There are two forms of balancing. "Static" and "dynamic". Static balance is to assure the "static" (or "still") weight of the parts match each other. "Dynamic" is the act of turning the crankshaft at a given speed, with "bob weights" attached (simulating the rods/pistons, etc.).

SAE (Society of Automotive Engineers) standards are that the balance must be within 1/10th of 1% of the rotating mass. In a V8, that's about 25-35 gr. When an engine is "balanced" at a performance shop, it is taken MUCH further, to within about 1 gr.

I suspect the old Ford truck you speak of, had the engine done at a dealership, where they "said" they sent it back to Ford. Chances are, it was done at a local performance shop. Not unlike the reman engines of today, people "expect" when they go to a dealership, the work being performed is "factory". Nope. Neither are those remans you get there for less than $2,000. They're "factory authorized" rebuilds. BIG difference...

In any case, it's always in the best interest of the engine's longevity to balance it.

Jim

SAE (Society of Automotive Engineers) standards are that the balance must be within 1/10th of 1% of the rotating mass. In a V8, that's about 25-35 gr. When an engine is "balanced" at a performance shop, it is taken MUCH further, to within about 1 gr.

In any case, it's always in the best interest of the engine's longevity to balance it.

Jim

ssssooo, gr = gram? will i notice a smoother idle? or smoother reving. or will it pretty much run the same... only now it'll last longer, with out wearing the internals.

All of the above...

Jim

cool, now does the same trick work on smaller motors, like 4 bangers. and sixes (slant or straight)?

ALL engines are "balanced" in one sense or another. If they weren't, they'd shake your fillings right out!

A "slant 6" and a "straight 6" are one in the same. Chrysler merely called their straight 6 "slant", as it angles over for better hood clearance. It's still a straight 6...

There are three basic "flavors" of multi-cylinder engine designs. "Inline", which we call "straight". Could be 2, 3, 4, 5, 6, 8 or more cylinders. There's the familiar "V" congiuration, which also comes in 2, 4, 6, 8, 10 and 12, as well as some antiques that actually had 16! Lastly, there's the "pancake" or "Flat opposed". This is like a VW (air cooled), Porsche or (ick) Subaru... These have all been popular at one point or another, in automotive applications.

FWIW

Jim

well the reason i pointed out the six and four bangers were more because of the varying degrees of seperation with the distributer. 8's are ussually smooth, 6's get a little rougher, and 4's are noticeablly shaky (because the distributer has to move 90 degrees to get to its next hit. < what i was trying to ask was will this shakyness lacken (dramatically, in the smaller motors) if i balance one, compared to non balanced (< well factory balanced if you prefer that term)

The "shaky" you refer to probably has nothing to do with "balance". It is the number of power "pulses" per revolution.

Mitsubishi and others have used "balance shafts" in their 4-cylinder engines, to try to eliminate some of the shake. The effect is marginal, at best. When we build a Mitsi that HAD them, we use an eliminator "kit". MANY a Mitsi 2.0 and 2.6 has hit the scrap heap due to a "knock" that was assumed to be a rod or main. In reality, it's usually one of the balance shaft bushings (similar to a cam bearing). For some odd reason, the FWD (transverse mounted) engines seem to shake less than the RWD (conventional) versions of the same engines.

Current versions of GM and Ford larger V6s employ a balance shaft, too. The whole idea is to offset the harmonics. V10s and V12s were originally designed for high-end luxury cars (in the '20s and '30s) for the smoothest possible operation. To this day, nothing has shown it's worth like V8, though. It has the best overall "balance" (not in the same context) of performance, reliability and smooth operation.

Jim

yeah i had a balancing shaft on my laser (1.8) i never understood it though mostly because it was shot... locked up and burned the belt off, but the car ran fine w/o it. <another part i didnt understand.

so that vibration doesnt go away though... hmmm. i guess something i could try are different styles of motor mounts to lessen that shake.