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Topic: V8 Pistons

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Eric Boyle

Re: V8 Pistons

#41

Home away from home

You guy's should really read this:

Quote:

First, the individual parts are weight matched. These include the pistons, rods and rings. There is not much you can do to the rings or rod bearings so, other than just setting up the "File-Fit" rings before balancing, all you do is supply a single set for one piston (3-piece oil ring, second ring, top ing) to the shop doing your balancing. First all of the pistons are weighed, then all the rods, locating the lightest of each. At that point, if you are reducing the weight of these items, machining the lightest of each component first. You now match weight of the pistons and rods.

NOTE: "All" other component machining must be done BEFORE balancing is attempted...!

The RODS are matched as "small ends" and "big ends". This means you match all the "big ends" by hanging on a special hanging fixture, then you do the same with the small ends. Be sure to double-check!

The PISTONS are also weight-matched, but the "material removal" machining is done either under the piston pin boss with a special offset cutter, or it is done by drilling holes (very carefully) on the surface of the pin boss. You do this to both piston bosses, sharing the material loss. You DO NOT want to remove the material off only one side.

The Damper, Flywheel/Flexplate, Pressure Plate, etc. are individually spin balanced. Just like the wheels and tires on your car.

After you have completed this weight matching, you are now ready to mount the Crankshaft in a special Balancing Machine that spins the Crank with the Damper and Flywheel installed, as well as "Bobweights" that duplicate the compiled weight of the Pistons, Pins, Rods, Rings, Bearings, and a calculated "weight of oil". The crank is usually mounted in Teflon or Nylon "V-Blocks" on the Balancing Machine. The Balancing Machine measures "out-of-balance" through Computer-Controlled sensors. Just like the way your wheels are balanced when you have tires installed (or hopefully during normal maintenance as well), yet the engine balancing machine is much more accurate.

Any errors in the balance of the crank is corrected by either:
Drilling to remove weight
Welding to add weight
Machining and Adding "Heavy Metal" (Mallory Metal)
The Balancing Machine in many cases has a Milling Machine built on to it, making quick removal of material. The Milling occurs on the crank's counterbalances. If metal (weight) needs to be added, it in most cases is done within the existing balance holes in the crank. In other cases directly to surface of counterweights. In only extreme cases, typically with very lightweight design crankshafts, is Mallory Metal used.

Source: Engine Balancing

Posted on: 2008/8/25 20:09

PackardV8

Re: V8 Pistons

#42

Home away from home

Certainly spinning the crank for balance check is an optimal idea. Spin it at various rpm. But how far out is the factory balance anyway to require a spin test???

Anyone that has ANY 4 or more cylinder cranks laying around handy give it a try. Just set it on 2wo level knife edges. Use a smoothed top 2x4 will even work and test the BARE crank at various positions. It will stay where ever u put it.

If u really feel the need to ad bob weights that are all each the same weight then put them on too. It doesn't matter. The bob weights mean nothing since they are added at equal offsetting points across the crank throws. Kinda like adding a 1 oz. wheel weight to your car wheel and another 1 oz weight directly across from it. What's the point???

My guess is that the article that T'Pacman sited was for balancing TWO cylinder engines of certain varieties. The writer of the article probably balanced HD engines which has become nearly epidemic over the last 10 years. They are balanced at approximately 60% piston/rod weight with such bob weights as sited. BUT 2wo cylinder engines, especialy Twins are completely different engine. Note that the article makes no statement about rod caps or bearings. He's probably talking Twins which in most (but not all) cases have not such caps or bearing shells.

Posted on: 2008/8/25 21:33

PackardV8

Re: V8 Pistons

#43

Home away from home

I guess everyone go ahead and have them balanced. I've never had to. But maybe the Packard V8 is problematic in the balance. I've only dealt with one running PV8 and a parts engine. All other types i've never had any vibration problems. And i have been spread rather thin over the years over a variety of engines.

Back to Jack's questions. I'm interested in the rod variations and Ford piston analysis too.

Remeber these???
packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=1307&forum=3

Rod pics:

packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=1364&forum=3

Posted on: 2008/8/25 22:07

gone1951

Re: V8 Pistons

#44

Home away from home

I've only rebuilt 4 engines ( not very many by any standards ) A 4 cylinder model A engine two 6 cylinder Chevy's and a 1955 olds V8. I didn't have any of them balanced in fact I didn't match weights of anything. Just installed the new pistons in the holes and ran with it. All the engines seemed to run fine. Just like they did before the overhaul. I even changed one rod in the olds because the old one bent when the valve broke and wrecked that cylinder. I was always under the impression that balancing was for the racing engines. Ones that had to turn 8 to 10K but for normal freeway cars it didn't make much difference. I have been told by people that their engines were balanced and to quote them "they really ran smooth and don't vibrate". Question would be how do they know at 60 MPH it wouldn't have been just as smooth unbalanced. I don't know but Id bet that when GM or Ford build their engines the rods, pistons and pins come out of a big pile with no more care than the weight tolerance when the parts were manufactured. The cranks are balanced but I think the crank alone has most to do with balance then the harmonic balancer and the flywheel. The small variation in piston and rod weights has little effect. Someone compared the rotating weight to the reciprocating weight and said that the rotating weight is what is important. I agree with that.

Posted on: 2008/8/25 23:09

Eric Boyle

Re: V8 Pistons

#45

Home away from home

It doesn't matter if it's a 1 cyl or a 16 cyl, it needs to be both static and dynamically balanced. It helps with the wear and tear on the engine, and allows you to rev higher. But, it's your engine, do what you want with it, put Egge pistons and don't balance it, then wonder why it doesn't last long.

Posted on: 2008/8/26 0:36

Jack Vines

Re: V8 Pistons

#46

Home away from home

Hi, Eric,

That article you posted is standard balance procedure which I/my balance shop do every time. You'll have to spell out for me (us) what you wanted us to learn from it.

Here are the reasons I balance every engine nowadays:
1. Packard's balance wasn't that great to begin with.
2. I bore many 352"s to 374" and the pistons are 38 grams heavier.
3. Egge pistons aren't even close to the Packard piston weight.
4. On custom engines, such as the 364" truck engine I'm building now, everything is modified.

Putting a bare crankshaft between centers or on blocks on the bench and watching what it does/doesn't do won't tell you anything about its dynamic balance. It has to have bob weights attached to the throws; they equal 100% of the rod big end/bearing plus 50% of the piston, rings, clips, pin and rod small end weight. Then, it has to be spun to operating RPM. If it were statically balanced, it would be all wrong dynamically.

thnx, jack vines

Posted on: 2008/8/26 14:43

PackardV8

Re: V8 Pistons

#47

Home away from home

I'm done with the balancing topic.

Jack, tell us about your truck engine. I assume the "364" was a misprint and should have read "374" ???

Are the F pistons u use a 4.125" diameter to fit 374 engine???

Posted on: 2008/8/26 15:05

Owen_Dyneto

Re: V8 Pistons

#48

Forum Ambassador

The discussion on engine balancing has been interesting, but let me bring this thread back to where it began for a moment. At that time I wondered what the level of interest would be in an OEM-style autothermic-strut piston for the Packard V8 as an option to the cast slug from Egge. I had broached the subject to Dan Kanter and he said he was willing to consider the project; thus I started the thread to see what level of interest there was, and for what sizes. Some of you responded with interest.

I saw Dan Kanter again at the Eastern Packard Club winter lunch a few weeks ago and again yesterday at the Packard East winter gathering; Dan said the engineering was pretty much done he was prepared to go ahead with the 352 and 374 pistons, presumeably in std and the various oversizes, given enough demand. He now asks that if you have a genuine interest, to please contact him at Kanter Auto Products. So now is our chance....call Kanter at 1-800-526-1096 and get the Packard department who can either transfer you to Dan or relay your message. I'd say it's now or never for this venture.

PS Dan gave an interesting talk at the event yesterday, recounting his adventures attending 16 national Packard Club meets, most of which he drove to.

Posted on: 2009/2/15 12:52

Owen_Dyneto

Re: V8 Pistons

#49

Forum Ambassador

Just trying to keep this fresh so everyone who might have an interest has the opportunity to see it and take whatever action they choose.

Posted on: 2009/2/15 23:36

Cli55er

Re: V8 Pistons

#50

Forum Ambassador

i will probably be interested in a set...but i am not to that part of the restoration. and as i am on a save as you go plan...i don't have the money for them now, that is reserved to get the frame done, then on to the drivetrain.

i will call him still to express my interest as these seem like they will be better than the Egge alternative (no offense Egge, as i thank you for at least giving us an alternative) 7 of my pistons are actually pretty good, just need to be cleaned up, but number 8 has a chunk missing from the top outside diameter. don't know why either....so i will probably go ahead and just get all new ones.

later,

Hank

Posted on: 2009/2/16 9:17

1937 Packard 138-CD Deluxe Touring Limousine
Maroon/Black 1090-1021
[url=https://packardinfo.com/xoops/html/modules/registry/View.php?ID=232]1955 Packard

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