17 replies to this topic

[greens nice]

hey guys just want to ask a few q's.
what do you use to keep a steel yellaterra flywheel on a hard revving 6
at six banger nats, got 6 1/8 mile runs in and then all the bolts have loosend out. all of them were finger tight and only 3 threads in except 1 which hit the clutch plate and snapped the head off .
bolts have come loose 4 times before.
have tried all different torque settings and made no difference.
when i pulled it all out (he made me lol) all the bolts except one was perfect
Moly lube on the thread and under the head like arp say is used, with a copper shim between the crank and flywheel.

dad used a std cast iron flywheel, copper shim and loctite before this and never had to touch it for 10 years.

clutch is sidestepped at 6500rpm and revs to 8000 in first second and third, over the line on the 1/4 at 7000
Whats the go? any suggestions?

Cheers, kevin

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Edited by greens nice, 11 October 2009 - 08:55 PM.

[dattoman]

I think this has been covered before

But I'll give you tyhe info on what I did when I spun the alloy flywheel off the datsun

Drill the crank between the bolt holes and put dowels in that help to locate the flywheel
Forget the lube on the bolts.... loctite instead
I used grade 12.9 cap head bolts and drilled thru the heads and lockwired each pair rogether so they couldn't come loose

Never lost another one

Don't like your clutch either....
Usually flywheels fall off due to harminics making the crank flex
Maybe you need a better balancer on the front too to help dampen the vibrations

[rodomo]

I don't understand the reasoning of having a soft metal shim (copper) between the flywheel and crank? I wouldn't use one.

I also wouldn't use loctite as loctite cures with pressure and may give a false reading while tightening up.

As this has come loose a few times now, there's every chance the flywheel no longer spigots snuggly on the back of the crank.
If this is the case, you will struggle to keep it on there.

[greens nice]

yer the clutch is f&$^ed now.

Mello: have used it with iron flywheel but arp say not to spose its time to use that again with no shim

Already has a 3kg romac balancer on it

kevin

[debkar]

Hi

After losing flywheel (and nearly a few toes) some years ago, I always use 2 dowels.

Black 3.3 crank has 1 already,

[lakeside]

clutch is sidestepped at 6500rpm and revs to 8000 in first second and third, over the line on the 1/4 at 7000
Whats the go? any suggestions?

my suggestion is you crack test the block and crank before you even fix your problem.

Had a 202 lc with the same problem. So i got 2 dowel in the crank by a mate. The sheared 7/16 bolts had smashed my clutch, new clutch and sent it off to be all balanced again. They told me to have it crank crack tested first and i did. The block and crank stuffed, a few more 8500+ revs and i would have lost my feet. Also when the engine came back from being balanced it had the flywheel/press plate doweled together.

[warrenm]

I had the same trouble on a speedway engine some years ago,then changed the company that was doing the balance work & never had another problem,i think they were using a set of bathroom scales to balance with. I use Loctite 641 super bearing mount on the flywheel & 243 stud locker on the 7/16" arp Chev bolts,& using similar revs to you with a smaller powerbond balancer. Have a talk to Mark Stewart(Panic),he has a method where he cuts a .005" groove in the crankshaft bolt up face that I think works pretty well.
Warren

[greens nice]

[/quote]
Have a talk to Mark Stewart(Panic),he has
a method where he cuts a .005" groove in the crankshaft bolt up face that I think works pretty well.
Warren
[/quote]


Flywheel is up getting that done atm
loctite, the groove, no shim and 2 dowels will all be tried next.
wouldnt surprise me if the block and crank are f*&$ed, theyve been in there for the past 12 years.

[warrenm]

I think the crankshaft face has the groove cut in it.

[greens nice]

I think the crankshaft face has the groove cut in it.

i was told it was the flywheel, turning it into a big spring washer.

[debkar]

Hey Torana_49

Unfortunately flywheel coming lose at high revs (7500 rpm) doesn't have a lot to hold it in place.

So since then as a matter of course, 2 dowels

Edited by debkar, 13 October 2009 - 09:37 PM.

[greens nice]

Anyone got a pic of this groove in the crank face?
What is the theory behind that?

ill post up a pic once the flywheel comes back from the shop.

basically, the groove allows the flywheel to distort slightly. so it tries to return to its orignal shape once tightened and pulls on the head of the bolts so there is tension on them, making the flywheel act like a spring washer in itself.

well thats our philosophy anyways......

kevin