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Discussion Starter #1
I have a buddy that's in the middle of swapping a 360 into his 258-powered CJ7... problem is that it need a new flywheel.

Does anyone know if the flywheel off of an 304 is compatible with a 360? I've talked to a couple of Jeep guys, and I've heard a lot of conflicting information... Anyone got any experience on this matter?
 

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Discussion Starter #5 (Edited)
Re: flywheel

porc said:
I have always told people they are balanced different(supposedly) but I sure have run alot of 304's on 360's and vice versa with no problems what so ever!
So do you feel comfortable running a 304 flywheel on a 360 if it's a trail only rig with a welded diff, cut boggers at both ends, and most of it's sheetmetal missing: I.E. it *ONLY* sees trail use.

But he likes the skinny pedal, so it'll get a workout at high RPMs... will this produce problems eventually, or what?
 

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i did the swap several years ago--had a 304 flywheel from a mill iwas gonna rebuild the foun a complete running 360 with a flexplate--was gonna use the 304 flywheel but because of the different balancing methods was told by a local amc guru not to do it. found a 360 flywheel for around $75. check it out carefully before you use the wrong thing!!!
frank
 

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They are balanced differently. You might try those guys in the upper right hand corner for a hook up on a new one. ;)
 

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I don't understand: How are the flywheels being balanced differently?

It's just a round, flat disk isn't it? Doesn't it have to be balance on it's own?

As you can see, i know very little about this. Just last weekend, I replaced my AMC 904 with T-176, but I have yet to fire it up. There were two positions where all the bolt holes lined up on the flywheel and the crank, i just used the first position that matched.

Was that in error?



:confused:

Edit: Blame Canada posting under Whizzy's ID.
 

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If I remember correctly the AMC V8 is not internally balanced or something.

You can use a 304 FW in a 360 but longevity of the engine will suffer.

Buy a new one if you wnat it to last.
 

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I went through this already when I did my 360 swap.

The 304 to 360 flywheel will work but, A new one from parts mike is cheap, I would just order one from him. Thats what I did.

I ran the numbers for both a 360 and a 304 flywheel and they do have different part numbers.
 

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mixmatching flywheels is a bad idea even at idle they are different for a reason
 

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I've been running for a 258 FW for the last 3 years in my 360, no problems at all... If you want to balance it to the 360, pick it up with the 360 crank and the harmonic damper and bring them to a balancing service.
 

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You need to get a 360 flywheel.

The 304 and 360 share the same crank and rods, but the bore size is different, meaning the pistons are different sizes as well. AMC V8s are all externally balanced and the 6's are internally balanced.

the higher rotating mass in the 360 needs a greater counter balance than the 304. I have heard of people putting 304 flywheels on 360's but the engines typically don't last long.

4wd hardware sells new flywheels for around $140 for the 360- I think they are new Mopar flywheels.
 

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amc v8's are externally balanced.. while the 258 is internally balanced.. meaning.. the flywheel from the v8's are balanced for that particular engine.. while the 258 is nuetrally balanced... so if you balanced your 360 with out the flywheel you could use a 258 one..

you can do it.. but you will hurt the longevity of the engine.. im no guru.. so i can not say on how long it would last..

the flywheels are balanced by drilling holes into the back of them.. to remove material at certain spots.. therefore balancing them to the engine..
 

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All AMC flywheels were balanced to the specific engine they came with.
Meaning, after the shortblock was completely assembled, it was spun on a big electric engine, and holes were drilled in the face of the flywheel, to dynamically balance each engine.

In addition to that, certain engines started off with a different flywheel blank, than others.
If you flip a 390,401, or 70/71 360 flywheel over, there is an extra weight cast into the other side. That's because these engines needed more help from the flywheel to set their balance.
72, and later 360's used the regular 258/304 flywheel blank to start with.
(This was also the year that the back of the engine cranks changed to fit the Torqueflite trannys, and the same year the L6's got the V8 bellhousing patturn).

So, the flywheels will all physically interchange, but the balance will be off.
Even swapping a flywheels between AMC's of the same displacement will change the balance somewhat.
'Some' level of unbalance was still considered acceptable by the factory, since the replacement flywheels they sold for these engines specifically instructed you NOT to try to copy the balance holes drilled on the original, when replacing it.

If the 360 your buddy has originally came with a flexplate (from an auto), I'd say his best bet would be to take the flexplate to a machine shop that can balance flywheels, and have him match whatever AMC flywheel he can find (off any AMC V8/L6 engine, new, whatever) to that flexplate.
 

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I ran a 258 flywheel for a few months and did not seem to have any problems. But i blew up my clutch so when I had it out I had a 360 flywheel sitting there So i put it in to see if there was any difference. I did notice less engine vibration. But other than that it was hardly noticable
 

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I just have to say, what a timely post.
I was gonna stuff my 360 into my CJ today and it turns out my old 304 flywheel won't work :D
Ordered up a new one at the local Action Auto for $50 plus core just thought somebody might need that bit of info.
:beer: to the PBB
 
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