bence13_33

I read an article about it and basically the machine shop takes your rotating components (balancer, flywheel, crank, rods, pistons) and evens out the rotating mass so that no one section is under any more strain than another....correct?

I'm probably going to have my 454 balanced by the engine shop. My rods are coming in next week along with my TRW forged pistons.

If a machine shop "balances" your engine, is the finished project an assembled short-block? I really kind of wanted to assemble the engine myself, but I'm sure this way will probably be more reliable. So can someone give me more information?

Stingy74

Yeah, I think you pretty much got it there Bence. They usually start with the lighest piston out of the set and go from there. If you want to assemble it yourself just tell them so. It would be a nusance though to disassamble and engine that's allready assembled.

ddn

bence: My machine shop wants $165 for balancing and $140. It's a seperate deal. I'm definitely going to have mine balanced, but assembly is still kind of a question. I'm sort of tempted to just spend the $140 and have someone at least sort of accountable if something happens to the bottom end. On the other hand I could save money and it would be fun.

Forum guys, especially those of you with experience, whats your opinion of assembling an engine if you've never done it before? I'm not too confident, but I'm willing to try if it's not stupid to.

1BadRat

Balancing does not include assembly, so you will be able to do that.

Being a 454(externally balanced), you will need to take the harmonic balancer and flywheel along with the crank to be balanced as an assembly. Good luck!

bence13_33

ddn:
My machine shop is asking $175 for the balancing, I'm not sure if that includes assembly or not. I hope it doesn't because I would really like to assemble it myself. Everyone on here is going to tell you to have the machine shop assemble it for you if you are experienced. There is really only one way to learn and it's not by having someone do it for you. However, there can be consequences to doing it yourself (i.e. engine comes apart). You just need to way the factors. I personally would like to say 100% truthfully that "I built it"....to some that's more important :).

Steve439

Balancing and assembly are totally different things. Probably the easiest
way to think about balancing is to think about getting your wheel/tire
sets balanced. The idea is to have everything weigh the same around
the entire rotating mass. Obviously an engine is more complicated....
Without getting over my head, you can just look at the crankshaft's
counterweights as weight on one side of the crank which counteracts
the weight of the rod journal/rod/piston weight on the other side.
You also want the piston/rod combos to weigh the same so they all
exert the same force as they move towards and away from the crank.

So to balance an engine the shop first weighs all the pistons and then
removes weight from the 7 heaviest ones to match the lightest one.
Then they do the same with the rods - and also try to balance the
weights of the big and small ends of all them. Then they take the
weight of the whole rod/piston assembly and make what's called a
"bob weight". This is a mechanism that fits around the rod journal
and mimics the weight of the rod/piston combo. One of these is put
on each journal and then the crank is spun on a machine just like on
a tire balancer. The bob weights aren't exactly the same weight as
the rod/piston assembly, but that really isn't important to
understanding the process.

The machine tells the operator where the counterweights aren't
correctly balancing the bob weights. The operator then drills holes
or welds metal onto the counterweights as needed.

This is getting to be a diatribe... Anyway, since your 454 is externally
balanced the counterweights don't have all the weight needed to
balance the assembly. So your harmonic balancer and flywheel will
also be included in the balancing.

So, it boils down to:

I'd for sure get the assembly balanced when swapping rods, piston,
or crank.

You'll get back the block - machined to your pistons, and the separate
crank and rod/pistons assemblies. Assuming you have press-fit pistons,
the shop will have fitted the rods to the pistons. You can then enjoy the
whole assembly process. It's my absolute favorite thing to do it terms
of working on cars.

Can a first-timer assemble an engine? Absolutely! Careful work and
double-checking will do the trick. I'd recommend buying the book
"How to Rebuild Your Big-Block Chevy" by Tom Wilson. It's a classic
and while it might seems kinda out-dated some things don't really
change much and it'll really help out sometimes.

I'm sure other guys will kick in if I've gotten anything wrong or
left anything out.

One last thing - I like drinking beer while working on my car, but I
think the actual engine assembly process is best done beerless....

Clink69

Just curious, why must the 454 be externally balanced? Isn't this a problem if you ever turn the flywheel for a new clutch?

. :flag

ram82fire

Bence the explanation by steve 439 is right on the money !!!!

BAD-L88

Externally balanced vs. Internally balanced

the 454 is "Externally balanced" so you have to balance the motor WITH the flywheel and harmonic balancer

As far as I know the 427 is "Internally" balanced. Correct me if I am wrong but this means that the balance of the engine is independent of the flywheel and harmoni balancer, that the motor can be assembled before the flywheel is even back from resurfacing at the machine shop.

Now, assuming that all I said abobe is correct, What makes a motor an Internal and what makes it an external?

BAD-L88

Answering my own question, a little:
http://www.secoperformance.com/Tech_Corner_April.htm

But this still doesn't explin why some are internal and some are external?

Pete79L82

The longer the stroke of the crankshaft, (454 big block - 400 small block) the more mass you need on the counterweights. The physical limitations inside the block restrict how much mass you can have on the crankshaft. So for the long strock motors chevy chose to externally balance them. The only other choice is to use what is called "heavy metal" and weld that into the cheek of the crank but that is very expensive, usually only done on hi-po motors. Because 454's where used on everything from trucks to Vettes Chevy went the more cost effective route.

bence13_33

Thanks to everyone who participated, this thread proved to be very informative! :cheers:

427V8

Another thig to remember is that ALL engines are balanced! Some are just balanced better than others :D

And blueprinting just means being more acurate on the dimensions...Which dimensions and how close to the design specs depends on who is doing the blueprinting
:rolleyes:

Also remember factory specs are not necessarily best for your engine:D