Balance Rotating Assembly ?

[jdbTSi]

Hello everyone,

Well I'm in the process of rebuilding my 6-bolt block and since
I purchased it without the balance shafts, I've decided just to
do the eliminator kit and be done with it. My understanding is
it is a good idea to get the whole rotating assembly balanced when
building a motor without the balance shafts. Now what is the
process that the machine shop goes through when they do this?
And this is done with everything assembled? or? I'm not too
knowledgeble when it comes to the machining/balancing of
a block so any tip/tricks to making sure the shop does it correctly
would be very helpful.

Thanks

 

[cmc]

Well...... They take each rod and piston and shave a little here a little there to make them all weight the same,(mitsu stuff is pretty close, especially 6bolt engines) then they assemble the piston and rod and weight them again. They then will put the crank under inspection and shave bits off of it so all lobs are equal! I did rhis to mine, and I can't tell that I have no balance shafts

 

[NDgsx]

Originally posted by cmc
(mitsu stuff is pretty close, especially 6bolt engines)

Not always though, some engines mitsu did a very good job. Some were just terrible. I have heard of one rebuild where the #1 rod was 10 GRAMS heavier than the rest! That's just ridiculous.

There are a couple of things that are done, cmc has the right idea, even though his terminology isn't quite right.

There are two things you have to worry about when balancing an engine, rotational weigh and reciprocating weight. Balancing the rods isn't making the overall weight even. On the end of the rods there are raised pieces in the forging, these are balancing pads. The machinist will basically hand the rod off the large bore and measure the weigh on the wrist pin side. Then he will grind down the balancing pads until all the weights come out equal. Then they hang it off the wrist pin side and balance the bearing journal side to match the rotating weights.
You can machine off metal from the pistons to match weights, but most of the time they are pretty well matched. This is overkill for most any 4G63.
Next the crank is balanced by itself (it is from the factory, but remember there is a little thing called production tolerances, they are not perfect). This assures that the main journals will be evenly loaded.
Finally the machinist will weigh each rod, piston, wrist pin, rings, and rod bolts. They fill little containers called "bob weights" with lead shot equal to the rod/piston assembly weights. These bob weights are bolted onto the crank, which is then spun. The machinist once again takes pieces out of the counterweights until everything is zeroed out.

Balancing a 4G63 to reduce vibration is fruitile, a inline 4 is simply not a well balanced engine lay out. Balancing for longer bearing life is never a bad thing though

 

[cmc]

Sorry NDgsx, down here in alabama, we don't use technical words, like technical, and all wheel drive. Instead we use "the $hit", and "yehah".
Also, all of the rods that come out of 6bolts seem to be pretty reliable as far as weight. I haven't seen one far off yet, but I haven't seen all of the ones manufactured, so I'm not an expert! Sometimes "lamans" is for any man.
I was really expecting my car to feel like a eighteen wheeler, but it rides very smooth!
And as far as the word "rotational" , It took me a few minutes to find it in the dictionary. I guess what it translates into in the "Back woods southern marry your ma and date your daughter dialect" is "spin that $hit"

Sorry I couldn't resist.