Packard Forum Index » Post-War (1946-54)

Eric, here's the other part of the equation. The crankpin length of the 356 is 1-3/8, but only 1-3/16 for the 359 engine. So not only are the main bearings longer in length, the crankpins are wider with wider rods at the big end and presumeably wider rod bearings. Thus to fit the package into about the same length of engine block, the crank cheeks between throws are narrower. Being narrower, they have less mass and since the diameter of them can't be increased, then the width (and thus the overlap) of the counterweight must be increased.

I think that should close out this very interesting diversion from the original topic, it's been fun, I never actually did the math on the bearing lengths, but I was confident that was the answer. More bearing area in the 356, both mains and rods.

The stroke on a 359 is 4.5".

And that's what I was thinking, Packard was trying to fit as much in the given space as possible, therefore all the "monkey business" with the crank and the counterweights. That, or when the 356 was developed, the engine of the day was the 320/385, and they just used what they knew, bolt on counterweights. OR, maybe it was just too hard to forge the crank and make it work without bolt on counterweights, and that's why they went that way. And as for needing more counterweight, it just makes sense since the rods being longer would obviously weigh more.

As for the hijacking, maybe Kev can divert this part to a new thread, and call it "Packard crank specs" or similar.

Maybe this is back on topic. Yes the weights for the 356 are cast and must be removed for grinding correctly.
As to cost. The last three I have completed cost between 6K and 8K depending on what components were missing or had to be replaced. That cost is from towing the car into the shop and driving it out. A complete turnkey. I'm in Missouri so prices are a little less here than at either coast.

The last time I had my machinist complete an extra 356 crank just to speed up the next rebuild.

EDIT: Oops forged is correct.

Dave, are you sure they're cast? I would think that they'd be forged like the rest of the crank.

For those who don't enjoy researching on their own, take a look at the #1 rod arrangement in the enclosed drawing from a 1947 Motor's Manual and you can very clearly see the encroachment of the counterweight (at bottom)over the rod journal which necessitates removal of the weight in order to grind the full width of the journal.

I hope this makes things clearer.

Attach file:

---

  (144.03 KB)

Some of use enjoy researching on our own, but lack all the necessary material to do said researching.

Thanks Dave. I went looking for an actual photo of the crankshaft on my 356 and forgot that I also had your diagram as well. If I can find the photo I will post it. It is very obvious why the counterweights have to be made to be removeable. I sure hope that I never have to have the journals ground.

Dave, I hope you never have to have your 356 crank ground as well, but let's have too much apprehension about it, I've seen it done by 2 different crank grinders and if they know their business, within the bigger picture of an engine rebuild, it's not really all that much of a deal. I'll try to get an "extra cost" estimate from the local crankshaft guys. I put in a call to them today.

Eric, if you can afford it, an older Motors's Manual is a great resource and at flea markets they are often $15 or so, try to pick one up. The one I use the most is the Twelfth Edition which covers 1935 to 1949 so it has the Twelves, Eights, Super Eights, 110s, 120s, 160s, 180s, right up thru the Clippers and the 22nd series.

Eric, For comparison attached is a diagram from an old MoToR's manual circa 1956 showing the 1951-52 "300" (327)engine. Note that the counterweights do not have an overlap.
Dave, I would appreciate finding out the approximate cost of a crankshaft regrind on a 356 engine.

Attach file:

---

  (250.95 KB)

I have several Motor's Flat Rate manuals, but that's about it. The do have a lot of good info inside, but not as thorough as it could be I would think.