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I'm rebuilding a 282", 15th.series. New forged pistons were made, they weigh 674.1-672.1 grams, the Packard manual states, " pistons in any one engine should not vary in weight more than 4 grams or 1/7 oz." The rods have been rebushed & the big end resized ( shop said cleanup &
true round) , NOS original style standard size bearings, the maxium weight spread on rods is 6.2 g
( not weighed by % of rod ). The damper stays where it stops on V-blocks & ball bearings. The flywheel & Pressure plate were surfaced and indexed , I was told the flywheel is "Neutral Balance". The crankshaft was cleaned / polished and measured .0014 under Packard minimum spec. of 2.0934" for rod journals. The main journals measured .0003 below Packard minimum of 2.7455-2.7465" using NOS standard size main bearings.
I don't like to shave /cut any more metal than necessary from crank, flywheel, plate.
I want this Packard to run Strong, Smooth & Silent just as it did in 1937.
I would appreciate any information / ideas about rebuild, especially balance.
Thanks,
Packard 385

My opinion - a good total balance job is relatively inexpensive relative to the total cost of a quality engine rebuild and I'd always go for it even in your case. Even if you did nothing to change balance, the factory balancing of the day wasn't done to as fine a degree as it can be done today.

When I had my 6 cyl rebuilt I asked for the engine to be balanced. When it was finished the shop owner told me that they balanced everything, but all of the parts were so close to being balanced from the factory that he thought that little was gained from rebalancing it. He said if all Packard engines were as close to being in balance he would not recomend the customer to pay to have it done. Maybe my engine was a exception to the normal. The engine was a 1947 taxi 6 cyl. Packardtaximan

From post #1.

"The damper stays where it stops on V-blocks & ball bearings."

Try the crankshaft under the same test. Probably have to use "knife edges" (a couple of lengths large level angle iron). A stock crank should stay at any position while rolled along the knife edges. I have at least 4 cranks here from Jag V12's, Pack V8, and 2.0 ford that will stay put on the knife edges regardless of how they are rolled along the top.
Also from post 1:

" The flywheel & Pressure plate were surfaced and indexed , I was told the flywheel is "Neutral Balance"."

Excellent idea on indexing the clutch cover wit hthe flywheel. Again place crank and flywheelassembly on knife edges and test. They should not roll under their own weight.

As for pistons the pistons are reciprocating weight and not related whatsoever in any way shape form or fashion to the balance of the crankshaft.

Piston weight variation from cylinder to cylinder is best kept small as possible but not critical (with in reason).

POINT 1: During the 30's or maybe 40's Buick factory engines had CI pistons. ONLY FACTORY AUTHORIZED replacements DURING the 30's was AL.

POINT 2. Dealer networks of any mfg'er have never 'sent engines out for ballance" during nor after field service overhauls.

Points 1 and point 2 above contradicts the sensationalism of "rebalancing" as part of overhaul process.

Over the years i've heard alot of sensationalism about various engine overhaul proceedures. Balancing and line boring (insert type) main bearings, decking heads just to be sure they are 'not warped" (when they are not warped to begin with) is all just for padding bills and gives the unsavvy owner some bragging rights. AND THAT IS ALL IT IS!!!

REad post #3 by Packardtaximan above. He pretty much syas it all in his post.

Over the years i've built up a variety of engines across a variety of mfg'ers,years and even applications. Some were just 'get me thru the nite" engines, some were very painstakingly and time consuming rebuilt to perfection.

Some were built from various misc parts of mixing pistons, main bearing caps etc etc from various engines. Never had any vibration problems or any of them fly apart prematurely.

Here it is in a nutshell and plain english:
The RE-balancing is a crock of shit.

The most important procedures of any engine overhaul is very close visual inspection of parts ( i use a magnifying glass) and hand fitting of the parts to as close to spec as is possible. This includes looking for variations in replacement parts relative to parts originaly taken from the engine. Some variations are very subtle but nonetheless critical. e.g. wrist pin offset of pistons if applicable.

Bearing fit and endplays are the most critical. Pistons and cylinder bores (condition) can get pretty damned sloppy and still produce an excellent long life engine. Even some room to fudge a little on endplays. BUT THE BEARING FIT IS CRITICAL!!!! ANY BEARINGS!!! of ANY component of the car.

Okay,

There are two types of motor balance. Internal and External.

An internally balanced motor is done the obvious way in that the crank and rods are balanced.

An externally balanced motor uses the flywheel to offset imbalance of the internal motor parts. Most V-8's are externally balanced meaning that the flywheel is matched to the crankshaft as a set. In those motors as long as the pistons and rods match the old stuff then everything will be fine.

Packard did not authorize rebabbiting rods and sold replacement rods according to casting numbers. They also authorized rod replacement with insert bearings which indicates that senior motors were externally balanced.

Proof would come from swapping a flywheel. If the motor then vibrates then it was externally balanced.

So..... if the rods are original and the pistons weigh the same as the old ones then you are probably okay. However, if your vibration damper is junk you won't know that unless you have the motor balanced which is a lot easier than putting it together and not knowing where the vibration is coming from. So balancing does pay, especiallly if you are doing a Packard 12 with a rotten damper.

Now what does an imbalanced motor feel like? Raise the RPM to around 2500 and you will feel vibration through the steering wheel. It will feel like you have a weak cylinder.

I just had the engine overhauled in my 37 120 and it has a balance problem as rpms increase. This shows mostly through the steering wheel. The starter gear ring was replaced at the same time. I have cheched the harmonic balancer amdclutch/pressure plate and all seems well. Ahy ideas on what to do to elemidate this will be appreciated.
Bart Morgan

Did the "balance problem" exist BEFORE the overhaul or u nevet drove it before the overhsul and don't know???

Thanks for the reply. No it did not exist before the overhaul.
Bart