'76 850 (85 hp) - Flywheel balance

[Smig]

Can the flex plate bolts affect flywheel balance? I took the flex plate off to realign the flywheel and did at least one, if not more, dumb thing(s). I know something is wrong because the flywheel makes noise as it goes around - it sounds like metal just barely scraping on plastic and it happens once per revolution. So here is what happened:

1) I broke a bolt putting it back on - will this one bolt head affect the balance? I am not that strong so I don't know how I did it, but it is definitly broken!!

2) I did not put each bolt back into it's original hole - I mixed them up. I read somewhere here that each bolt has a slightly different weight so when the flywheel is built, this is taken into account. Is that true? If so, how do I go about rebalancing it?

Why did I take it off in the first place? Well I am asking myself the same question - I just bought this motor and found that the flywheel was not put back in the right place. The previous owner replaced the trigger and when he put the flywheel back on he aligned the .464 mark on the sticker with the actual TDC of piston #1 making it impossible to time the engine. I took out the 8 bolts of the flex plate, rotated the flywheel and then bolted it back up. Now everything aligns and I can time it properly, but there is that noise and the broken bolt.

Thanks
Shaun

 

[emckelvy]

Re: '76 850 (85 hp) - Flywheel balance

Shaun, did you get the backing washers on correctly? One is supposed to go between the flex plate and the center hub, and one on top of the flex plate for the bolts to bear against.

I wouldn't think that part of one bolt being broke off would affect the flywheel balance to an extreme degree.

I've never heard anything about bolts being weighted differently and have never had this kind of issue with flywheel reassembly no matter where the bolts went.

Maybe you should disassemble the flywheel again and see if you can pinpoint what's rubbing. Check the stator carefully to ensure it's bolted down firmly. Also check all the seating surfaces of the flywheel flex plate, backing washers, and center hub.

If there's rust or debris on any of these parts such that the flywheel can't sit evenly, it may cause issues.

And it definitely would be a Good Thing if you can extract that busted bolt. They're Grade 8 or so and quite hard, but a very hard drill bit might be able to penetrate. Then you can perhaps use an EZ-Out along with a little heat to free up the busted part. Just don't break off the EZ-Out as it's even harder than the bolt!!

HTH & G'luck.........ed

 

[Smig]

Re: '76 850 (85 hp) - Flywheel balance

Thanks ed - you have given my mind a bit of peace, I was worried about the bolt weights.

You may have found the problem - I did not see that there were washers under the flex plate. Let me make sure I have the terms correct here: The flexplate sits on top and bolts through the flywheel into the hub. There were definetly washers with the bolts, but I didn't see any washers under the flexplate. I never lifted the flywheel from the hub - I was so concerned about alignment that I just rotated it one bolt hole and bolted it back together.

By the way - do you know what the flexplate bolt torques should be? My manual only gives the flywheel bolt.

Thanks for you help - I will disassemble the flywheel and see what I find. I'll post a follow up

Shaun

 

[Chris1956]

Re: '76 850 (85 hp) - Flywheel balance

Smig, There is a single washer under the flexplate and a single washer over the flexplate. I do not remember if the 5/16" USS bolts has washers, but I do not think so. I also cannot believe the balance of the flywheel would be thrown off by the breakage of one bolt.d