Tore my 327 down to calculate the compression ratio, & it was low (8.5) with the cast dish pistons. I want to install flat-tops and power pak heads to bring up the squeeze, but the new hypereutectics are qute a bit lighter. How will this affect the crank? Do I have to have the whole rotating assy. balanced? it may be more cost effective to buy a pre-balanced rotating assembly.

If the new pistons are lighter, you will have to rebalance.
If it's all tore down all ready, it won't cost that much to have it balanced.

Best $300 you can spend on balancing imo.Hypers are inexpensive and you have rods and a crankshaft hopefully reuseable.if not..then a pre balanced rotating assy may be a viable option.Typically these kits fall into acceptable ranges for street/strip usage.
Fwiw..do you know any one that buys 4 new tires without balancing?

The machinist took a look at the crank & told me its too grooved to be polished. Needs to be cut. So with the cost of that, the new pistons, and the balancing, I'm at about $700. I found an Eagle rotating assembly (383) for less, so I think I'll convert this block. It's what I really wanted anyway. Thanks for the advice. I'm still curious what would be the outcome if we had changed the pistons & not balanced it?

Best $300 you can spend on balancing imo.Hypers are inexpensive and you have rods and a crankshaft hopefully reuseable.if not..then a pre balanced rotating assy may be a viable option.Typically these kits fall into acceptable ranges for street/strip usage.
Fwiw..do you know any one that buys 4 new tires without balancing?

Actually, I do know of one guy that doesn't get his new tires balanced. This is a true but also hard to believe story. His WIFE won't let him spend the extra few bucks for balancing. She told him they were brand new and shouldn't need anything extra. All of us tried to explain it to him but apparently she wears the pants in the family and controls his wallet. This same guy gets $20/week for spending money, period! PW at the max!

The machinist took a look at the crank & told me its too grooved to be polished. Needs to be cut. So with the cost of that, the new pistons, and the balancing, I'm at about $700. I found an Eagle rotating assembly (383) for less, so I think I'll convert this block. It's what I really wanted anyway. Thanks for the advice. I'm still curious what would be the outcome if we had changed the pistons & not balanced it?

You are headed in the right direction with a balanced kit, even better if it all forged. This is the time to check deck clearances. Deck it to get the most out of your combo. Order the pistons to match you head, tighten up quench, bring up compression.

Balancing is best on any motor. However, weight is being subtracted evenly across the cylinders and the difference between the two pistons' weight is not going to be enough to matter unless you were going to race the motor a lot.

Balancing is best on any motor. However, weight is being subtracted evenly across the cylinders and the difference between the two pistons' weight is not going to be enough to matter unless you were going to race the motor a lot.
That's exactly what I was thinking. If I don't rev this thing to the moon, I can probably get a few years out of it, and avoid the expense that would double the cost of what started out to be an inexpensive rebuild. How about polishing the journals by hand? I read about someone doing this with 2000 grit sandpaper and a shoelace wrapped around the journal.

That's exactly what I was thinking. If I don't rev this thing to the moon, I can probably get a few years out of it, and avoid the expense that would double the cost of what started out to be an inexpensive rebuild. How about polishing the journals by hand? I read about someone doing this with 2000 grit sandpaper and a shoelace wrapped around the journal.

For a backyard grocery getter build..you will be ok not balancing..maybe.
Its not all rpm and hp..an imbalance can occur at cruise rpm and will drive you crazy.Typically..a rebuilder set of new pistons can vary alll over the place.No gaurantee that they all weigh the same.
As for the shoe lace polish on a scored and tapered crank journal..forget it.Run around all the journals with a micrometer and then get back with your machinist and beg his forgiveness for doubting him.

Just remember that the crank kit you are looking at probably isnt balanced either,most of them arent.Even if the crank itself is advertised as"internally balanced" doent mean that it is actually balanced,it just means that the crank has enough weight on it that the balance shop will be able to internally balance it without adding any weight to it.Most crank kit companies get an additional $200 to blance a kit.If the kit is externally balanced{like most lower dollar kits are},you will need a 400 dampner and flexplate/flywheel for your setup too.

If the kit doesnt come in the box with a "balance sheet" that includes the weight of each component in the engine along with the bobweight and percentage,I wouldnt consider it balanced.

Good luck.

BTW,I buy Eagle rotating kits{really good stuff} but they arent blanaced unless you pay extra.I just payed $200 each to have 2 496 kits balanced from them last month.

im thinking if an assy is already balanced and you replace the pistons with a set of new pistons that all weigh the same as each other, then you will be ok. Not ideal, but ok. I think any decent set of pistons from JE or Venolia, etc should all weigh the same as each other.

Having everything weigh the same isnt the same as having it balanced.The crank counterweights must carry enough mass to offset the weight of the big end of the rod and a percentage of the top half of the rod and piston,whenever any of these things changes a rebalance is in order.Some builders will say that it is not a big issue to have a crank that is weighted a few grams too heavy rather then too light.In reality if it is close and all the parts do weigh the same,they are right.A new rotating kit must be balanced though.

Balancing a new rotating assembly is cheap insurance. Do it!

Polishing the journals is something else that can't hurt as long as its not over done so much that bearing clearance or fillet radius is messed up. For street it's not necessary.It's usually one of the seemingly million small steps a guy will do to get every little bit out of a motor.