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Old 09-28-2008, 02:49 PM
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tgreese tgreese is offline
Join Date: May 29, 2003
Location: Medford MA USA
Posts: 11,514
Curious - why is a 304 flexplate different from a 360?

Just wondering - I know that all the AMC V8s are externally balanced with unique flexplates, flywheels, balancers, etc. etc.

I can see why the 401 would be different from the 360 (different crank), but I understood that the 304 and 360 cranks are the same. I've also seen claims that the 304 and 360 cast factory flywheels are the same except (maybe) for the drilled balance holes.

Which is it, and if the 304 and 360 cranks are the same, what part of the rotating assembly is different enough to make the balance different between the two engines? Did the factory use the same flywheel casting for the 304 and 360 and machine them differently? If so, how to tell the flywheels apart after they have been separated from the engines?
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
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Old 09-28-2008, 03:11 PM
eyotajeeper eyotajeeper is offline
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Join Date: Feb 13, 2006
Location: Iron Range, MN
Posts: 156
Here is a photo of a 360 flexplate on the left and a 304 on the right.
The difference being in the bottom section cutout.
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Old 09-28-2008, 03:54 PM
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Lindel Lindel is offline
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Join Date: Jun 15, 2000
Location: Carpentersville, IL 60110
Posts: 9,204
The difference would be the piston size. The bore on the 360 is bigger than the 304. That's also the reason the heads are different as well.
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Old 09-28-2008, 04:51 PM
rowdy235 rowdy235 is offline
Join Date: Sep 26, 2008
Location: Sweet Home, Oregon
Posts: 247
I am facing this issue right now as the newly rebuilt 304 included with my jeep (with blown 360) doesn't have the flexplate. Oddly enough the f.p. for the 360 is cheaper than the one for the 304. Not fair IMO.
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