Hey guys, Trying to learn more about flywheels and flexplates, how they work, their relation to dampers, cranks, bellhousings, ect.. Been researching for my swap but wanna know what these things actually do and how/why they work. Anybody have some good links or threads to check out? couple of threads I've seen.. http://mmb.maverick.to/showthread.php?t=22936&highlight=302+flywheel http://mmb.maverick.to/showthread.php?t=51896&highlight=flywheel http://mmb.maverick.to/showthread.php?t=49329&highlight=flywheel http://mmb.maverick.to/showthread.php?t=13788&highlight=flywheel&page=2 http://mmb.maverick.to/showthread.php?t=12916&highlight=flywheel http://mmb.maverick.to/showthread.php?t=7693&highlight=flywheel&page=3 http://mmb.maverick.to/showthread.php?t=22936&highlight=302+flywheel Just starting my learning and this is what I've read so far. I'll keep searching but feel free to bomb me with some info if you've got it! Oh - This one just seemed silly haha http://mmb.maverick.to/showthread.php?t=71639&highlight=flywheel I like you guys better than wiki
a flywheel is for a clutch. its heavy to provide a rotateing mass to provide inertia to keep the motor turning between piston pulses at low rpms. a flexplate is for automatic trans. the conveter provides the mass for the inertia. they have to match the balance to the balance of the motor. that is determinded by the crank, rods, pistons and balancer. there are different diameters also. that has to match the bellhousing so the starter will be in the right location to properly engage. those are the basics of flywheels and flex plates.
This is all of the top of my head someone please clarify if there is a mistake. For SBF your basiccally using either a 157 tooth or 164 tooth flywheel or flexplate, with either a 50oz balance or a 28 oz balance. Like Bryant stated balance has to match rotating balance, harmonic balancer, and flywheel/flexplate. Diameter (tooth count) has to match the bellhousing being used, and then you also need the correct starter and block plate for that bell/flywheel combo. 351's have a 28oz balance 302's/5.0's have both balance.early being 28oz late being 50oz I believe the switch was 1982 meaning later will have 50oz. 289's 28oz also a note on 289 early bellhousing have a 5 bolt bolt pattern.
I like this link here. http://www.mustangcentral.net/tech/c4.html Tells a lot about the c-4 and which flexplate to use.
In addition to the above info, Flywheels and harmonic balancers also absorb the vibrations produced by the engines power pulses so that: a. the engine tends to continue to rotate and doesn't destroy itself with "harmonics" created on every power pulse. Think about what happens when a u-joint fails or a driveshaft slings a weight. The difference in the engine is that it's twisting forces along the crankshaft's axis that are being absorbed instead of the off axis forces from imbalance. The external weights in SBF's are because of the designed in imbalance. b. so your extremeties don't go to sleep from the vibrations like you're cutting grass on that old POS lawnmower.
In addition to all of the above, the Mustang II 302 used a 147 tooth flexplate and matching smaller bellhousing.
This is some awesome info guys! Thanks! That C4 link is pretty sweet. Alil overwhelming lol. All that about the vibration and twisting definitely makes sense - don't know what happens when a u-joint fails or driveshaft slings a weight, but I get the premise. novice followup questions: How is the flywheel related to the crank? I think I'm starting to understand its relation to the harmonic balancer.. And is there any history or reason that they have different numbers of teeth and different balances? Why change it in the early 80's? Have to do with the switch to roller cam's? Also for future novice's "SBF" stands for "Small Block Ford" - googled that one haha
In the early 80's Ford obviously made a cost cutting decision in reducing 10 or 20 pounds of weight from the 302 crank. The imbalance was made up thru larger counterweights on the flywheel/flexplate and the harmonic balancers. To see this, you need to set a 50 oz crank side by side with a 28oz crank. The counterweights of the 50's are smaller by about half. The amount of weight added to the flywheel/flexplate and balancers is far less than what was removed from the counterweights. And when you consider they cast millions of cranks for these motors in the following twenty years, and multiply even ten pounds of iron, that's a huge savings in production cost. Just 10 pounds X 1 million cranks adds up to ten million pounds of iron, that's a huge chunk of change. As for your question about it relating to the switch to roller cams, that didn't happen for another 4 years afterwards.
That was a really good explanation! Thanks! I had no clue that the cranks were even changed. Makes total sense.
You definitely want to make sure you match the flywheel/flexplate to the carnk. When I was young and dumb I used the wrong plate on a 300 six and it wanted to shake all your fillings out of your mouth! Never forgot that lesson.
...year doesn't dictate the balance weight...my '93 roller was...28 oz... the crank balance is the key... ......
think of it this way: the flywheel is a heavy wheel that once it is put into motion, it tends to keep turning, hence inertia wheel, like Bryant mentioned. The weight is matched with the engine based on what it will be used for (car, truck, forklift, etc) and the balance needs of the crank. The harmonic balancer is actually a damper (but in the case of the SBF, has a "balance" weight attached) that cancels out the harmonics produced by the engine during the power stroke.
Like Frank is showing here, once you go aftermarket crank you can switch to any balance you want. But the one thing that is the same your rotating assembly, flywheel or flexplate and harmonic balancer all have to match on balance. You can even install older 28oz stuff in a new roller block if you want it just has to all match. The block does not car what balance it is it just all has to match. Take a look at say a fidanza aluminum flywheel, you can interchange the weights for either a 50oz balance, a 28oz balance, or a zero balance, by either switching or removing the weights completely. It just gives them the versitility to make one setup for sale, instead of 3 different part numbers for 3 different parts.
just a quick question guys, what the difference between internal and external balance, say i have a 157tooth 28oz internal balance and a 157tooth 28oz external balance whats the difference?
