360 vibes Part Deux

[dodger1]

I finally got around to pulling the crank on my 360 which had an untraceable vibration problem despite being a built and (allegedly) balanced stock crank and rods short block from a reputable shop. (Ref, 360 vibrator, Nov/05 here) Attached are pics of what I found. We have NO idea of the purpose of the plug welded into #5 counterweight, but it's pretty obvious what the result was on #5 main brg., especially considering the appearance of the other 4 mains. The machine shop that has it now is puzzled as well, I'll let you know the results he gets when he re-balances. All I can say at this point is - tough crank!!

[dwc43]

I have never seen a crank with mallory metal in the outer edge of the crank throw like that. It's usually put in the side of the throw. Looks like you found your problem. Do you know what machine shop that it came from? I'm sure if you post it no one will want to use them anymore ... lol.

[dodger1]

dwc; me, a mech, and the machinist who is gonna do the re-balance think that the plug we see is nothing more than a common pipe plug or threaded core plug; not Mallory metal, none of us have any idea why. I didn't know Mallory plugs were inserted from the side of the c/w but that makes sense. Thanks for the info. Anyone else got ideas as to what the welder thought he was doing?

[dwc43]

I looked at the pic again. Not sure what it is, but I think your right. It's not mallory metal. Not the right color from what I can tell from the pic. There's a pic with some mallory metal in the side of the counter weight.

[LA360Dart]

Hi All;

I had a 340 that this was done to, it brings into balance the crank, without using very expensive mallory metal(common metal plug). Damage you have is severe to say the least. It did shake from the very start. The only thing I can think of is alignment of engine to bellhousing...

Denny

[George G. Leverette]

A torque convertor will also produce a lot of vibration if not balanced correctly. What type of material is the bearings composed of? The piece of metal welded to the crank appears to be a cheap way of bringing the crank into balance. Please keep p[osting results.

[dodger1]

The vibration was not affected regardless of whether I used the stock (LA360 weighted) converter or the B&M weighted flex plate (10239) and a 318 neutral-balance unit. I'll post the shop's findings when I have them.

[dodger1]

Here's what needed to be done. Apparently the rear of the crank was 140 grams out of balance, probably connected to the 2 iron pipe plugs welded into the rearmost throw. Dave (Precision Performance Machine, Penticton BC) wound up filling and drilling the rear counterweights as you can see, and here's the kicker. The B&M flexplate had to be modified severely as the unbalance part was about 90 deg. off. Not sure if the plate was wrong or it was just a result of getting the whole shebang to balance, but it's done. Bonus points to Dave for catching a stress riser on one conrod, and returning everything in immaculate condition. It'll be a while before it's back in the car but I'll post when it is. Your comments on the extensive surgery are invited.

[George G. Leverette]

It's nice to see there are still some shops around that can produce excellent machine work. Is the cost of all that work close to the cost of a new crank? waiting to hear how the car runs with the crank mods.

[dwc43]

Originally Posted by dodger1

Here's what needed to be done. Apparently the rear of the crank was 140 grams out of balance, probably connected to the 2 iron pipe plugs welded into the rearmost throw. Dave (Precision Performance Machine, Penticton BC) wound up filling and drilling the rear counterweights as you can see, and here's the kicker. The B&M flexplate had to be modified severely as the unbalance part was about 90 deg. off. Not sure if the plate was wrong or it was just a result of getting the whole shebang to balance, but it's done. Bonus points to Dave for catching a stress riser on one conrod, and returning everything in immaculate condition. It'll be a while before it's back in the car but I'll post when it is. Your comments on the extensive surgery are invited.

I'd keep an eye out on that flex plate. Hope it holds up cause your going to be in a mess if it breaks due to stress. You'll be looking at another engine balance and build. That's the only complaint I got. The crank looks good, but that plate is scary. I would have got anotehr crank and plate before I did all that drilling on the plate. Good luck with it and let us know how it turns out in the long run.

[dodger1]

We discussed another crank but Dave felt this one was good to go. I sort of concur on the flex plate - but he felt it would hold up fine as this is not a high-rpm motor.