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Flywheel question

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GremlinP38 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GremlinP38 Quote  Post ReplyReply Direct Link To This Post Topic: Flywheel question
    Posted: Aug/13/2019 at 8:12pm
can I run a 71 360 stick flywheel on a 72 up 360? I’m betting not but I need a flywheel and I’ve got a guy who says he has a 70 to 74 360 flywheel. I know that shouldn’t be correct and I plan on looking at it in person to see for sure what it is. I have a temporary engine I want to run for a couple summers while my 390 is being rebuilt. Actually have it in but figured out I have the wrong flywheel and vibration as a result.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 10:10pm
1970 and 71 360 crankshafts have a flat end on the crankshaft, 72 and up have a stepped end. so flywheels are not interchangeable unless you use an adapter. same is true for a automatic transmission flex plate.
Best to have him provide a cast number to verify the year or measure the diameter of the hole as they are different.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 10:12pm
So that is the number of the flywheel you currently have? I might be interested in it if will work for one of my engines.

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myrambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 10:15pm
Is your 360 a virgin engine, never been rebuilt? If it has been rebuilt you likely will need to have the flywheel balanced to the engine. If stock and the correct 360 flywheel is used you may be ok without vibration issue.  
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GremlinP38 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GremlinP38 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 10:36pm
The guy with the flywheel is interested in trading possibly for my flywheel. I have suspicion it is a 290 or 343 flywheel. Engine has not been rebuilt. I know or at least I remember now that ‘72 up centers on the step , but can you get away with the older flywheel like I have currently on there that stops short of the step and centers on the crank. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 1970390amx Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 10:58pm
If I remember correctly a early crankshaft is 4". A later flywheel is slightly larger like 4 1/8 maybe. A early flywheel on a late crank is very dangerous it cant set flat on the crankshaft. a late flywheel on a early crank has nothing to center it except the bolts.
1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box
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myrambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 11:04pm
the flywheel crankshaft recess measurement on a pre 1972 engine is 4.50", a 72 on up crankshaft recess flange diameter is 4.65, so the matting surfaces are different diameters, in theory you could bolt a late flywheel to an early crank but it won't fit tightly and you are relying on the bolts alone to keep it attached. not good. I don't think its possible to bolt up a pre 72 flywheel to the larger diameter crankshaft flange. so what year is your 360? is it a stepped or flat flange on the end of the crank?
  
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GremlinP38 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GremlinP38 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2019 at 5:54am
Ok, that answers some of it. I have a stepped crank 360 and the flywheel on it right now does not center on the step. Didn’t feel right but a friend of mine assured me that it was fine. The current flywheel has no counterweight and from what I can tell from info I found from Eddie Stakes and one other source it’s probably a 290 or 343 flywheel. Obviously the flywheel this guy has can’t be a 70 to 74 360 if there is a diameter difference in the end of the crankshaft size. Not sure of the year of my 360. It was a freebie from my grandfathers brother. They had it in a Matador that they wrapped around a tree and it ran well enough that they kept the engine, but never ended up with something to use it in. I’ve never cared enough to decode the tag. I’m curious now. It does run well.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GremlinP38 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2019 at 6:03am
Eddie Stakes says 304 did not have a counterweight. A very detailed page I found says 304 and 360 shared a flywheel with counterweight from 72 to 78. I had a 72 Gremlin 304 that was incredibly smooth that I pulled for a 401. When I took the flywheel off the 304 it had a counterweight, but it also had a bolt welded on it. I’m guessing hillbilly balancing? Main point is I’m wondering who is right and does 72 to 78 304 and 360 use the same flywheel (outside of the individual engine balancing)?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote myrambler Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2019 at 8:09am
if you have a stepped crank flange then your engine is a 72 or later engine. Much easier to find a correct flywheel for. 70-71 where flat flange less common. Send me a text msg and I can forward pictures of different flywheels stored on my computer. 
Mike
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