M11 bolts in 40mm???

Posting for a friend who's doing an LS4 Fiero conversion. To make his clutch work, he needs roughly 40mm long flywheel bolts. The longest we can find is 29ish mm used in the CTS-V. No bolt supplier seems to carry these (incl the usual suspects like McMaster). Some have suggested that this isn't actually a metric size but an imperial one but we tried their suggestions and while the diameter is close, the pitch is out to lunch.

Any ideas/sources guys?

Must be a real thick flywheel.

What about getting some m11 all thread and welding a nut on then cut to fit. Not a perfect solution but might work.

For a flywheel you'll need strong bolts, don't scrimp. Have you checked with ARP?

40mm = an inch and a half. Today I bought an M-12 that was 4.5 inches long, granted it was an 8.8 and you want a 12.9 grade, but I can't believe it's that hard.

Maybe I misunderstood the question.

Dan

mcmaster carr

Is it really m11? Or m10. Mc master carries just about everything and I can't even find anything m11 thread.

$1.

http://www.boltdepot.com/Product-Details.aspx?product=6769

mcmaster p/n 98093A761

Yup, definitely M11. Even tried calling GM and they said they don't make them anymore and neither does any fastener supplier they know of.

And yeah, these are flywheel bolts so McGyvering anything isn't an option.

We tried ARP but their shortest M11 stud is really long (specifically, the unthreaded part is too long)

Latest news is his clutch maker may be able to offer him clutch plates with a different center (concave) so he can remove/reduce his flywheel spacer.

Try a head bolt from something?

Head bolts are usually M11 or M9, I am assuming because that helps prevent cheap bastards from using generic fasteners in this critical application. (Hint)

It also means that engines can yield a surprising number of "bucket bolts" that are completely useless.

Can you have a machinist drill and tap them for m12x1.75?

Taiden wrote: Can you have a machinist drill and tap them for m12x1.75?

I agree. Tapping to a larger size is the way to go. And why stay metric. Going to a 1/2 -13 size is much more common and easier to find in a high grade bolt. I bet ARP selll something that you can use.

I suggested going 1/2 inch as well since the diameter of the thread root of the 11mm hole may leave a 12 mm thread not fully formed.

^^ There you go

If you go with 1/2", it's 1/2"-20 you want, not 1/2"-13

change to studs? try metric screw and tool in Wakefeild mass. They have it all.

http://www.metricscrew-toolco.com/

I don't find an M11 size listed.

either M10 0r M12

M11 would be very close to 7/16"

did the LS4 use metric flywheel bolts ?

It really bugs me that it's m11. Makes me wonder if the fastener is being measured incorrectly. I noticed that you didn't spec the thread pitch too. Have you taken it to a fastener specialist to get it specced? We have this place in Portland called KL Jack and those guys are crackheads with their fasteners. If Portland Maine has it, someone in Toronto has it.

It is M11 for a reason. That way no one can replace them with the wrong spec bolt. In the same way that M12X1.50 thread pitch is very hard to find in regular grade bolts and is the standard for european car wheel fasteners. That way Joe Hamfist the backyard mechanic can't go and use 5.5 class chinese bolts to hold the wheels on the car.

I can understand that reasoning, but it's still awkward.

But it is also very smart. You have to respect the engineer that thought it up.

Call Maryland Metric. Their website, marylandmetric.com is completely useless, but they've found me some really oddball bolts before. If they don't have it, it probably doesn't exist. Though I like the tapping-a-new-thread idea.