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PostPosted: Thu Jul 07, 2011 8:13 am 
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Joined: Fri May 23, 2008 9:34 pm
Posts: 362
Location: Hamden, CT
I'm replacing my 225mm flywheel bolts with new ones. Oddly, although the holes in the flywheel appear clean and undamaged, there is some freeplay around each bolt. The stock bolts don't have a raised shoulder to fill this gap and the the bolt is the same diameter for it's whole length so this spacing may be normal.

Does anyone have a flywheel out of the car they can test with a bolt to see if they also experience the same freeplay?


See my video below.

http://www.vimeo.com/26091105

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed


Last edited by Datsun Z Garage on Thu Jul 07, 2011 2:52 pm, edited 1 time in total.

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PostPosted: Thu Jul 07, 2011 11:19 am 
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Joined: Thu May 28, 2009 3:44 pm
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Location: Massive Sangwich
I haven't experienced anything different from what I can remember. I'll see if I can test that when I go out to the garage later, as I have both a 225mm flywheel and the 240mm aluminium flywheel which I use. I can't imagine the bolt freeplay being an issue, as the real area of concern is the step machined into the flywheel that mates with the flange on the crankshaft. This needs to be a tight fit for it to be centered perfectly, something which my aftermarket flywheel was not. The machine shop put a slight knurl in it to tighten the clearance.

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PostPosted: Thu Jul 07, 2011 11:21 am 
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Joined: Wed Apr 09, 2008 5:53 pm
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Location: CT
weird.

Certainly call Vinny Bedini about that. He's changed more flywheels in his lifetime than he can count.

860-355-18-twenty nine.

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PostPosted: Thu Jul 07, 2011 2:39 pm 
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Joined: Fri May 23, 2008 9:34 pm
Posts: 362
Location: Hamden, CT
According to Vinny the play is normal.

I notice the Datsun shoulder is flush with the bolt threads instead of being raised. Seems counterintuitive but I looked online and many bolts actually are fully threaded instead of having a shoulder like the Datsuns. For some reason it looks like a raised shoulder on flywheel bolts isn't that common, hmm.

He also said to never to use an impact wrench on flywheel bolts since it ruins the small threads on the bolt.

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed


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PostPosted: Thu Jul 07, 2011 3:16 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 14779
Location: CT
Weirder and weirder.

I've never heard of 'loose' bolts on a flywheel (or any other major part of a car, for that matter). Any GM engine I've ever put together had flush-mounted bolts and specific torque requirements. I learn something new every time I open this website.

No wonder some of our guyz have taken to safety-wiring their flywheel bolts on!

There has to be a sound mechanical reason for this. I wonder what would happen if we (you) eliminated the play? It doesn't appear to be that much travel/movement, but it must be there for some good reaZon. I'll spend some time thinking this out. What possible benefit could there be to having free movement in the flywheel bolts?

Come to think of it, I had a 1951 James motorcycle with a Villiers engine in it years ago. The clutch was multi-plate with cork inserts, and those flywheel bolts moved a bit, too. I thought I wasn't cranking them down properly.

Hmmmmmm........:? Think think think.

Frank

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PostPosted: Thu Jul 07, 2011 3:57 pm 
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Joined: Fri May 23, 2008 9:34 pm
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Location: Hamden, CT
They're not loose when torqued down...just that there's slight clearance around each bolt.

I'd still like to hear from others...PhrogZ46...what did you find?

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed


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PostPosted: Sat Jul 09, 2011 10:45 pm 
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Joined: Fri Nov 14, 2008 1:50 pm
Posts: 605
Location: Putnam Valley, NY
I find that there is a bit of slop when you test fit only one bolt. It has to be there for clearance and tolerance stacking, otherwise it would be a press fit. By the time you have all the bolts threaded through the flywheel and into the crank, all of the spare room has been absorbed by tolerance stack. In other words, bolt 1 might be all the way to the left in the hole, while bolt 3 might be all the way to the right in its hole. By the time you subtract all the tolerances of the bolts, and torque them into place (I like to use locktite red for good measure), you have a pretty solid connection that will not be a problem. Play is normal and if you feel nervous, try to get some new bolts for the installation.

To illustrate this:
Put the flywheel on the crank and thread in one bolt hand tight. Now grab the flywheel and twist it to take up the play in that hole to one side. Now snug the bolt with a wrench. You will have a tough time trying to get all the other bolts to thread in by hand. That's because they aren't all EXACTLY in the right place. Tolerance.

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76Z Turbo'd
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PostPosted: Wed Jul 13, 2011 8:57 am 
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Joined: Wed Jul 23, 2008 2:38 pm
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Location: rhode island
Yea, sounds OK. The indent on the back is important, but with all the bolts started in the holes there will be slight play until tightened down. Always use the RED lock tight. I do a 3 time tightening pattern as well. snug, tight, torqued.


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PostPosted: Wed Jul 13, 2011 1:57 pm 
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Joined: Fri May 23, 2008 9:34 pm
Posts: 362
Location: Hamden, CT
Thanks...after getting new bolts and doing a test I agree...once things are snugged down there isn't much play...I think I made it a bit over-dramatic in the video.

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed


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