Balancing at Machine shop

[jayro]

I am building a 3.2 for my 94 mtx and am taking the rotating assembly in to get balanced. I have searched and found alot of useful info, but my question is this. What is the difference between a zero balance and a 51% overbalance (a definition of each is kinda what I'm looking for). I know there is dynamic and static balancing, and from what I've read dynamic would be the way to go because it takes into account all the forces. I am also going to have my flywheel and harmonic dampner balanced seperatly. My engine is cammed so it does see 8k from time to time. Thanks

 

[jayro]

Anyone?

 

[gmail]

as i remember it over balance isnt gonna be needed for you its normally used in extreme builds where you have lightened or modified the rotating assembly in a extreme way.

the overbalance is used to take in account oil or other factors on the pistons or rods etc.

for example overbalance or 52% takes into account for 2 percent of oil weight on the pistons.

like i said i could be wrong this is what i recall.



a zero balance should be all you need.. you dont plan on running 8000+ rpms all the time i think you would be fine

 

[jayro]

a zero balance should be all you need.. you dont plan on running 8000+ rpms all the time i think you would be fine

Thanks for the info. No, I dont hit 8K very often...only every once in a while if Im not want to upshift and then down shift a second later for a turn. My normal aggressive shift point would be between 7k and 7.5k.

 

[Phoenix]

Having it balanced is nice but far from a necessity , none of my builds got balanced and im hitting 8K often in my 2002.

Do it only if your budget permits it. Its not something you will regret if you dont do it. Just saying.

 

[gmail]

Having it balanced is nice but far from a necessity , none of my builds got balanced and im hitting 8K often in my 2002.

Do it only if your budget permits it. Its not something you will regret if you dont do it. Just saying.

yeah agreed if you dont have aftermarket pistons or whatever dont worry about it.

just make sure everything goes back to its home and its all good..

i rebuilt my 3.2 and i took it all apart cleaned everything, scrubbed the pistons, valves etc like a mad man then put the rings back on and everything was perfect.

i did cold compression a few months ago and cold compression was like 170 or 190 or something i dont even recall...

its even seen 8k plus many times

so back to the point if your keeping oem stuff dont bother a balance..

 

[jayro]

Having it balanced is nice but far from a necessity , none of my builds got balanced and im hitting 8K often in my 2002.

Do it only if your budget permits it. Its not something you will regret if you dont do it. Just saying.

Thanks for the info. It is something I budgeted for. Plus It needs to be balanced cause the crank is from another car. The original owner of the engine had the old crank turned down. Not a big deal since I had a source for a good crank and already was planning on a balancing job.

 

[rbruso]

Okay, so here's a related question.

I'm assuming the 3.2 and 3.0 pistons & rods are a different weight. So, if you were doing a 3.2 upgrade by using a set of 3.2 pistons & rods with a 3.0 crank it should need a rebalance, right?

 

[gmail]

Thanks for the info. It is something I budgeted for. Plus It needs to be balanced cause the crank is from another car. The original owner of the engine had the old crank turned down. Not a big deal since I had a source for a good crank and already was planning on a balancing job.

but yes id advise to get the crank balanced because it has different pistons and rods.

id recommend to save some money, getting a scale weight everything then give it to the machine shop to balance the crank.

from as i hear it will save the guy at the shop time and in return you money.

 

[Phoenix]

Okay, so here's a related question.

I'm assuming the 3.2 and 3.0 pistons & rods are a different weight. So, if you were doing a 3.2 upgrade by using a set of 3.2 pistons & rods with a 3.0 crank it should need a rebalance, right?

Both 3.0 and 3.2 cranks are the same

The cranks are balanced standalone style BEFORE they were installed in the motors at the factory , regardless if it was 3.0 or 3.2.

I really doupt the balance spec changed from the 3.0 to the 3.2

 

[gmail]

Okay, so here's a related question.

I'm assuming the 3.2 and 3.0 pistons & rods are a different weight. So, if you were doing a 3.2 upgrade by using a set of 3.2 pistons & rods with a 3.0 crank it should need a rebalance, right?

anytime you mix and match anything in the rotating assembly. even if its the same kind of engine for example a 3.0 crank to another 3.0 engine.... balance it... my opinion

nothing is copied perfect so the weight will be off in different areas from things like bad castings and air pockets.
if i recall the story a few years ago bizzy sent out a bunch of 3rd gets both new and used, had them checked and only a few of them were good like no micro fractures, it wasent because of used or new just because nothing is created equal.

even a few grams at several thousand rpms would become like the weight of bowling ball... im stealing that from area91 (sorry i probley messed that up but you get the idea)


also tho people will argue that the a balance dont amount to much that the dampener does the work and its true you cant balance for every rpm, just impossible

 

[yamahaSHO]

With everything out, there really is no reason not to balance, unless you're that broke.

Even with my boxer motor build, I'm looking to possibly get a balance.

I did a zero balance on my build. It handled 8k RPM in stock form fine and my balance is probably more accurate. The engine runs fine. At that point, you need to look at oiling. I limit at 7.5k now.

 

[gmorrell]

If this is a mix/match of crank, rods and pistons, just have the machine shop balance it, most especially if you have plans to twist it to 8K RPM, even just occasionally.

When I built my 3.2L blower motor, the shop zero-balanced the rotating assembly, then they added the crank damper and rebalanced it by adjusting the damper balance, then they added the flywheel and rebalanced, then the clutch cover and pressure plate was bolted to the flywheel (no disc obviously) for the final balance. Once the crank and bob weights are on the machine and into trim, it's relatively easy to add the rest of the rotating components and trim them into balance as well. My 3.2L was just stupid-smooth, and I believe the extra care in balancing was the reason.

 

[Eric VerValin]

You taking it to C&P?

 

[jayro]

You taking it to C&P?

Either there or a machine shop here in auburn. Havent decided quite yet. The shop up here builds alot of engine for local racers.

 

[Eric VerValin]

Well for that type of work, I can tell you the guys in there all have 20 years of experience doing it... I dont think they have one guy in that shop under 45.. lol Cant say enough good about the head work they did for me. I still get 30+ mpg on the highway.. and for some heads with about 250K and the original shims that says a lot..

See what they want pricewise too.. they seem to be pretty cheap on the big stuff.

 

[jayro]

Well for that type of work, I can tell you the guys in there all have 20 years of experience doing it... I dont think they have one guy in that shop under 45.. lol Cant say enough good about the head work they did for me. I still get 30+ mpg on the highway.. and for some heads with about 250K and the original shims that says a lot..

See what they want pricewise too.. they seem to be pretty cheap on the big stuff.

I have heard good things about C+P. I talked to other machine shops in the area who actually send there stuff to C+P to be done. I am planning on having the heads done too. New guides and seals. Not sure about getting a 3 angle valve job.

 

[Eric VerValin]

I thought about it this way... when doing that valve grind... it makes the valves essentially longer, so you never have an issue with shims, if your ok with them trimming the tops of your stems.. They said most of mine were right at spec with the shim that was there after the grind.

I got stem seals from SHO source, and they had no problem putting my parts in... there is one older guy who does the "newer aluminum" stuff, and he did 3 other SHO's before mine. He's been there before.. They are also very good with finding parts too..

Stop in and talk to em, they'll b/s with ya or whatever to see what ya want..