Ok, heres the deal. I had my 383 rotating assembly balanced about 3 months ago. Im just now dropping the motor in the car, and then I came across some posts saying that a 168 tooth flywheel (which is what I bought ) wont fit in a stock T-5 bellhousing. I still have my stock LO3 flywheel I can go with, but the guy at the machine shop said he couldnt balance it unless he had the crank and balancer (anyone else wanna call BS on that??). So anyways, I got to looking at the 2 flywheels and noticed that they both have kind of a counterweight on them. The guy at the machine shop said hed have to look at it, but thats a good drive and Im runnin our of free time. He said throw it on and if it vibrates, Ill have to take the motor apart and get everything rebalanced.

Im guesin they balanced the whole thing, balaner, flywheel and all, together as one unit. That way if I have to replace anything, Ill have to get it rebalanced again!!!

Im going to call a few other machine shops in the area to see what they think, but look at the flywheels. The counterweight looks remarkably similar. Im still kinda lost on exactly what internal/external balancing is. Ive heard of external being the rotating assembly and flywheel with a neutral balancer, but Ive also heard heard that its a rotating assembly with a neutral flywheel and counterweighted balancer. someone help me out here!!

Pic 1: both flywheels side by side. 168 tooth on left, stock 153 tooth LO3 on the right.
http://memimage.cardomain.net/member...33_11_full.jpg

Pic 2: a better look at the counterweight on the LO3 flywheel
http://memimage.cardomain.net/member...33_12_full.jpg

 

First off, does the 383 you built have a 1pc rear main seal or a 2 pc?

From the looks of it, it's a 1pc., correct? If so, and if your machinist did NOT remove or add any weight to the flywheel to balance the rotating assembly, then the one off your LO3 will work.

All flywheels for Gen I and Gen II SBC engines are counter-balanced exactly the same. They're "universal" for lack of a better term.

If your 383 uses a 2 pc rear main seal crank, then you don't have to worry about it because the bolt pattern is totally different than your LO3 flywheel anyway.

 

ya, your right. its a 1pc RMS.

And no, he didnt add any weight to the crank. He took some out, took some out of the flywheel, and barely any at all on the balancer. But both those flywheels int he pic are for a 1pc RMS

The LO3 flywheel hasnt been machined past resurfacing. its never been balanced, so there are no balance holes drilled into it

 

Then he screwed you.

There is never any reason to balance a rotating assembly by adding or removing weight from items that are all balanced the same from the factory, be it a damper (not "balancer") or the flywheel/flexplate.

Now you have to have him balance the entire assembly using the new flywheel.

To make sure he doesn't screw you, tell him he shouldn't charge you for re-doing it since he screwed it up in the first place. And this time he needs to balance it WITHOUT adding or removing weight from the flywheel. That way, if by some act of THE ALMIGHTY, you crack your flywheel, strip out a hole, chip or break some teeth, etc., then you can easily get another flywheel to replace the existing one and not have to worry about balancing anything.

 

I agree, but I wouldn't take anything back to him. Find someone else that knows what they are doing. I would find someone that knows how to balance a rotating assembly, cut my losses, and have it done right. Just my opinion.