Packard Forum Index » Pre-War (1899-1942)

I think this thread is going overboard. Imbalance in an under square long stroke motor like a Packard is going to have a magnified effect if the replacement parts do not weigh the same as the original parts.

If NOS Packard parts were being used to overhaul an engine then rebalancing would be a waste of time. Once I compared the weights of an original '33 Super 8 piston to a popular cast replacement brand and they were nearly identical.

However, on that motor job the original rods were welded, rebored, machined with an iron thrust surface,and fitted with rod bearings from a Chrysler 360 V-8 or something.

So who wants to guarantee that job without a rebalancing?

There is more to balancing than the crank. The counterweights have to be adjusted to match the reciprocating weights. So if you bore a cylinder the reciprocating weight will change and require a rebalancing.

There is motor overhaul and there is motor rebuilding. The two are not the same. Dealers overhaul motors. They do not rebuild them. An overhaul is a repair not a rebuild.

Next issue is align boring main bearing caps. This process involves milling the caps and then resizing them to correct out of round conditions. If you are overhauling a motor you don't bother with this.

Finally, I don't think any of this modern super computerized machinery is doing a better job of balancing than the Packard company did. For one thing these machine shops are still under the shade tree, whereas the Packard company was a manufacturing plant. Just because a torque wrench has buttons on it doesn't mean it is going to be more uniform than a good old fashioned Sturtevant heavy beam torque wrench. To say otherwise is like saying that computers improve arithmetic.

I'm sorry to say that post #22 didn't have any engineering background, just conjecture, plus thinking the Packard Factory was good in their design and manufacture of engines is a MYTH. They were terrible. I've been redesigning and remedying their design problems for many years. I received a PM today which I'm not bright enough to understand. Someone in Elkhart,IN that restores aircraft. I've been advising those people for yrs. Often tell the FAA they couldn't fix a bicycle. It baffles me that guys don't want to learn. A&P guys scare the H out of me w/ their lack of knowledge but they dive right in because they have their ticket and it doesn't matter to them if the craft goes in. Deal w/ it all the time. I've not said anything of my background and can't understand why the possibility of helpful advice is threatening to some. Is this Site a closed society? Went professional in '52 and have kept diligently studying ever since. Ought to take what I have to offer before I'm gone, kids. Cancer is not fun. David

Crankshafts:
Take ANY counterweighted crank from ANY mfg'er of engine (assuming auto or lite truk application) and place it on two SIMPLE TO MAKE knife edges that are leveled.

The crank can be rotated to any radial position and it WILL STAY IN THAT POSITION!!! It is a FACTORY balance of the crank, exactly the crank and ONLy the crank with absolutely NO consideration for piston weight.

The counter weights exist to counter the thorw of the rod journal.

OK. Now, bore the engine for real heavy or real lite pistons and butcher up the counterweights crank all in the name of "balancing" annd then the crank will no longer stay on the knife edges and will rotate to the position where the rod journal of the crank is at the BOTTOM unless weight added t o crank counterweights then crank will rotate with rod journal to top.

Upsetting the crank balance.

Piston weight has absolutley no bearing whatsoever on crank balance. Neither does rod weight. OTHERWISE the crankshaft of a production engine would not stay at ANY poisiton on the knife edges.

Disclaimer: my above decription does NOT apply to 1 cylinder nor 2 cylinder engines. ONLy applies to 4 or more cylinder engines.

I don't know about 3 cylinder engines.

Here is a thread from about 3 years ago:
Start at POST #1 of the thread.

https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=11532&forum=1&post_id=119739#forumpost119739

Poor eyesight, too. I meant post #21. Long day. I start at 2:00 AM. David

ok. So just exactly how is the crank "rebalanced" for heavier pistons or rods????

Suppose i build an engine with heavier pistons. Now, is weight added to the crank or is the crank lightened???? Add weight to counterweights or grind weight from counterweights.

Just exactly what changes about the crank are needed to compensate for the heavier pistons?????

Does the crank get lighter or heavier???

replying to post #23. Mr V8. I'm sorry to say that everything you say has been absolutely wrong in all your posts on this subject. It's obvious you don't have the slightest clue.It's a real disservice to the members here to feed all your wild off the wall statements. I'd be happy to explain with facts if you're interested. I don't enjoy turmoil or upsetting anyone but there are some here that would like the truth. David

Hate to say the knife edge balance of the crank by itself is incorrect or just per chance poss due to some engine designs like inline sixes and eights. A v6 or v8 of a 60 degree design or 90 degree is balanced with bob weights simulating the big end weight of the rods. The 2 rods on a throw ARE rotating weight and the crank counterweights must account for that. V8 cranks are most certainly not balanced bare. At 400 - 2600 rpm imbalance may not be an issue but if your turning a small block to 6500 or 7 grand or higher I think you had better equalize and spin balance.

And yes. Weight is sometimes added to a crank. You never heard of Mallory metal? It is added as slugs to holes bored in the outer face of the counter weights and welded in . It is heavier than the material removed thus adding weight.

Custom Clipper . Yes, Sometimes Heavy metal(almost pure tungsten) is added. It's installed axially w/ press fit , no weld needed or wanted. I hate to say the tens of thou tied up in stock.