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Old 06-15-2002, 10:29 AM
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Default Balancing Act

I have a street stock with a 318 V8, not enough ponies even for a dry slick track. I am replacing it with a 360. To make the change easier, I had the 360 internally balanced, so I could use the same torque converter as the 318. Has any one done it this way? Will the 318 flex plate bolt on the 360 crank? The attached balancing image shows how everything is added up, even the oil on the moving parts, to come up with the total weight.
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Old 06-15-2002, 10:34 AM
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Default Balancing Act 2

Here is what was added up: Pistons and Pins, Rings, Rod Bearings, Connecting Rods, and "Estimated" Weight of the oil. After the weight is figured, small metal shot is weighed on a scale to match the total weight times two minus the weight of the bobweight itself. See the shot being weighed in this image.
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Old 06-15-2002, 10:37 AM
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Default Balancing Act 3

Step 3 Now the shot is poured into metal cylinders on the bobweight. After that metal caps are screwed down on top of the cylinders to keep the metal shot from coming out. See image 3.
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Old 06-15-2002, 10:45 AM
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Default Balancing Act 4

Step 4 Now the bobweights are placed on the rod journals, and the entire assembly is rotated and balanced like you would balance a tire and wheel assembly. Unless you are running lightweight pistons and rods, you will have to add weight to the crankshaft. The Heavy Metal they add is called Mallory Metal. Sanborn was right, he said that it would take two metal plugs at each end. See image with the crank on the stand and one bobweight attached.
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Old 06-15-2002, 10:48 AM
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Help Balancing Act 5

I need more help. I understand that the mounting ears on the side of the block are different for a 360 than a 318. When making the swap, what is the best way to fix the motor mounts? I am sure some of you guys have done this before. I am putting the engine in a '74 Charger. If you have any other suggestions, I would appreciate them. Thanks for your replies.
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Old 06-15-2002, 02:34 PM
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I externally balanced mine, cheaper and if you break a crank you just balance another on and use the same flexplate(b&m)
As for the motor mounts, I too ran a 318 before and just used the 318 mounts, I think its the driver side, bolt it up with a bolt that will hold it and tighten it up. Now all you need to do with the remaining bolts is slide washers in thereand put your bolts in and tighten her up, I got a different set for the 360 and I welded the washers to the mount , now I have a 318 set and 360 set for about 10 cents. I also leave the mounts on the 318 so it is less to switch if the time comes, along with water pump, alt, and powersteering and pulleys, dist and carb too.
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Old 06-16-2002, 09:08 PM
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rolleyes2 Flexplate

Cageman. Do you use a B&M flexplate like the drag racers use? Does it have any advantages over a stock one? I thought they were thincker and HEAVIER? As far a balancing, I don't plan on breaking any cranks (WHO DOES), but even if I were externally balancing an assembly, I would still have to rebalance a new crank if I had to replace one. I thought it would be worth the effort to go with the Mallory metal and do it internally. You can run a better harmonic dampener and you don't have to fool with weights on the torque converter, plus if I switch to a stick shift I can run any flywheel. Thanks for the info on the motor mounts. Can't wait to fire that 360 up!
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Old 06-17-2002, 10:03 AM
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Default

Years ago(15+), a very good friend and I had a balancing machine and we ran it as a back yard, small business.

We got into it in order for us to experiment with piston, rod and crank lightening techniques. We learned a lot. We could get a SB Mopar Crank down to about 48 pounds(when using lightweight pistons) and could even get a 3.75" BB crank down to 58 pounds ( with lightweight pistons)! Six to eight pounds off a crank means a lot for acceleration off the turn! We also lightened TRW pistons, pins, etc. At that point in our lives, we needed something to keep us "off the streets" and also provided a little $ for our racing activities.

My good friend (George) got good enough that he could mark the spot on a crank that we were going to have to drill(or grind) away weight before we spun the crank. The same thing with adding heavy metal! Mopar cranks were very consistent, GMs were fair and Fords all over the map!

One of the lessons learned was that stock steel cranks, rods, etc. were very HP sensitive. It would only take so much torque before failure. But there was still plenty of stock stuff around and since we couldn't afford pure racing components, that's what everyone used.

We really didn't make much money(not on an hourly basis) because we tended to try to get a balance job perfect. We would get rods(both big and small end), pistons, pins, harmonic balancer and the crank balance within 1/2 gram. We also did a lot of rebalance work- assemblies that had already been balanced by another shop. We found our tolerances were much closer that most- we found a lot of assemblies were within as much as two grams! There is a lot of difference in time between a tolerance of two grams and 1/2 gram.

We sold the equipment and records about 8 years ago( I didn't have time any longer and George was experiencing some health problems). What surprised me was we had records of over 200 assemblies over that 8 year period. That was a lot of balancing for a back yard, cash only, "word of mouth" little business. That didn't include the custom crank, piston, harmonic balancer and pin lightening work.

The whole purpose for this post and explanation is this-if you destroy a crank, you can remove the "heavy metal" easily and you can get another stock crank and by comparing measurements install the "heavy metal" before balancing. Then, a balance shop would only have to "touch up" the balance work and you would save some $.
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Old 06-17-2002, 05:15 PM
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Im sure its the same as the drag race type, Yeah I know you can reuse mallory but that stuff is expensive and I dont do my own engine building. I use a 318 t-convertor too, but I used the stock dampner also. My crank only needed two spot welds to balance out, it was the easiest crank they have done. I have the only balanced engine in my class so I dont talk about it to the locals, they would assume its a high dollar cheating motor
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