I've read about using the GM bolts, ARP Cam Bolts, and even the L9 bolts from David Kerr that I've had. I've trashed a flywheel in the past when my L9 bolts broke. I don't think this was install error, as they were on there for a long time, years. I drive my car hard, and beat the hell out of it at every opportunity I get. I'm putting together another F23 set up, using a SPEC Aluminum flywheel, and my old SPEC clutch parts. I really don't want this breakage to happen again and ruin the expensive flywheel. While I've seen the bolts listed as 5/16-18, no one seems to specify the length they're using.

Thoughts, suggestions?






RESULTS:

SPEC Flywheel, use 1" flanged bolt.
STOCK Flywheel, use 1" hex bolt with washer.

[This message has been edited by Jncomutt (edited 04-03-2013).]

8x GM p/n: 24505092, torque to 11 ft/lbs in 1st pass, then turn an additional 50 deg in the final pass. You can use a drop of red loctite on the threads of each bolt for some added security if you want.

I've never seen new GM flywheel bolts for these engines ever break when they were torqued properly. I have seen them break when people have tried to REUSE them.

I've heard of the ARP bolts coming loose and I've heard of GRADE 8 and L9 bolts breaking (probably all due to the incorrect torque specification being used for the particular bolt). You CANNOT use GM torque specs on bolts that are not identical to the bolts GM sells.

-ryan

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OVERKILL IS UNDERRATED

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

Thanks Ryan. I think I'm going to get the GM ones and give them a try. I wonder if the bolts are coming loose or just breaking? I did use loctite on mine, and followed the spec supplied with the bolts. Like I mentioned, I had these on my car for a while before they quit, and I wonder if there might be more to the story...

quote Originally posted by Jncomutt: Thanks Ryan. I think I'm going to get the GM ones and give them a try. I wonder if the bolts are coming loose or just breaking? I did use loctite on mine, and followed the spec supplied with the bolts. Like I mentioned, I had these on my car for a while before they quit, and I wonder if there might be more to the story...

Looking at your picture showing the broken bolts, it appears to me that they were overtorqued and simply snapped off.

quote Originally posted by Darth Fiero: Looking at your picture showing the broken bolts, it appears to me that they were overtorqued and simply snapped off.

I was thinking the same thing...

Interesting that they lasted so long 'overtorqued'. I'm not ruling it out, my torque wrench could be wrong, but they were set to 19ft-lbs back in like 2009 or so, oh well.

quote Originally posted by Jncomutt: Interesting that they lasted so long 'overtorqued'. I'm not ruling it out, my torque wrench could be wrong, but they were set to 19ft-lbs back in like 2009 or so, oh well.

Well if they were overtorqued, they may not have been so far so to break immediately but they might have been weakened to the point that they would eventually fail from something as simple as thermal expansion and contraction.

Where did you get the 19 ft/lbs torque spec from?

I got the spec from David Kerr, who I bought the bolts from. He got that spec from the supplier, iirc.

do NOT use the GM FW bolts on this setup. The Spec aluminum FW is thicker where it mounts to the crank. You will only get about 1/4" of bite... You'll see. Also the bolts that mount the PP to FW that SPEC included are not long enough... Luckily I noticed right away when my PP to FW bolts came loose, these should have been torqued to 28 ft/lbs. I was told 14 ftlbs (same at the FW to crank).

(I am running f23 - SPEC 4+ - SPEC alum FW)

http://www.futek.com/boltcalc.aspx

[This message has been edited by slideways (edited 12-11-2012).]

Slideways, what bolts did you end up using?

If the SPEC aluminum flywheel is thicker than the stock cast iron flywheel, then I agree, DO NOT use GM flywheel bolts. But whatever bolts you get - you need to make sure you speak directly with the manufacturer and get the proper torque specs from them for the bolts you are using.

Good luck!

[This message has been edited by Darth Fiero (edited 12-11-2012).]

If you torqued the L9 bolts to 19 ft. lbs., then that was correct according to the manufacturer.

What kind of HP are you running with your 3800?

--david

Last time on the dyno it made 519hp, and about 500tq. I did a few things since then and was probably about 525whp.

quote Originally posted by Jncomutt: Slideways, what bolts did you end up using?

Keep forgetting to measure the extras I have in the shop, I'll get back to you.

But I can tell you the FW - Crank bolts were 5/16" - 18 Grade 8.2

FW - PP bolts were metric I used 12.9's and they were 1/4" longer than the ones from SPEC

Got them all from HD supply, the 5/16's were some kind of aviation grade at $6 a piece...

I bought 1996 Firebird 3800 w/ 5 speed bolts from the dealer and they were too short. IIRC I went to fastenal and purchased some bolts 1/4" longer than the GM ones. Sorry I cant be more help.

[This message has been edited by BV MotorSports (edited 12-12-2012).]

I guess I should mention... Some argue using 8.2 bolts can cause premature wear on the other components because they are stronger and harder than the female thread and the component being fastened. But in this case I dont think that applies. Cause really the bolts aren't under any varying tensile load, like say a head bolt. The only load the FW bolt SHOULD ever see is the initial tightening from you, the bolts are simply pressing the FW to the crank and friction is doing all the work. I chose to use 8.2 for that reason... But I am no expert, with that kinda power you might want to look into it a little further before using 8.2

Maybe I need to measure the surface area of the crank face that the flywheel mates with. From there I suppose I could figure out the amount of torque required to overcome that bolted joint. Then again, the way an ICE creates torque pulses, Idk how relevant it would be

I'm not sure about the Fbody, but the SPEC is pressed on. When I initially tried to install it I thought it was a design problem but after talking to Jeromy at SPEC he assured me it was designed like this. The center hole on the flywheel is a calculated diameter smaller than the collar sticking out of the crank. I actually had to torque the bolts down in 5 - 8 steps to make sure it gets pressed on nice and evenly. It took about 8ft/lbs on each bolt before it was flush against the crank (final step I used 14-16ftlbs) Although its only pressed on a 1/4 - 3/8", its stuck on there good! You'd really have to pry it off to remove it. Not sure if the camaro FW is like this, but thats an extra bonus for friction

[This message has been edited by slideways (edited 12-12-2012).]

SAE grade 8 bolts are typically 930MPa ultimate tensile strength depending on surface area/size, but that is their rating none the less. around 136,000psi shear. 8740/arp is 1040MPa UTS again depending on surface area/size, and rated at 180,000psi shear. most bolts shear are a 60-70% of the actual UTS, making the grade 8 more like 150,000psi and the arp around 200,000psi. i dont know who the l9 bolts are made by but personally i would just use the arp bolts, use arp lube and torque accordingly. my .02 cents

Slideways, thanks for that info on the hub.

Well I did some checking with the SPEC flywheel. Both flywheels are .840" from the crank mating face to the friction surface. The SPEC flywheel does fit snug on the crank as Slideways mentioned. However, I noticed it is much shallower than the camaro flywheel. Below are some pics with my existing L9 bolts.

SPEC Flywheel, for reference:


Camaro bolt depth:


SPEC bolt depth:




I have to check the SPEC clutch disc to see if the spring pockets are the same radius from the crank centerline as these bolt heads. I'm worried that with similar bolts, the clutch disc might end up rubbing the bolts.

For future reference, I measured about .470" for the thickness of the flywheel where the bolts pass through. Assuming a .060" or so washer, .570" bolt head to the crank face. At 2 x dia. this gives roughly .570" + .625" = 1.195" bolts. In real world application, that's a 1.125" bolt providing roughly .555" engagement, or roughly 1.75 x dia.

Any opinions?

[This message has been edited by Jncomutt (edited 11-12-2013).]

Okay, well my last post was incorrect. In real life, that equals a 1.25" bolt, since grade 9 isn't offered in 1.125". That will leave me with just over 2X diameter engagement (.680"). I'll order these 1.25" 5/16"-18 bolts from Fastenal tomorrow, with washers..

Bolts came in, I had to order a pack of 25, so I have extras if someone else needs a set. Now, to figure out this clutch disc clearance issue which gets more interesting since the new washers measure .070" - .080" compared to the 060-065" of the old ones (unless they were deformed).

[This message has been edited by Jncomutt (edited 01-11-2013).]

ARP part number 3AG1.000-5CL

http://autoplicity.com/prod...6_18_1_000_bolt.aspx

ARP jumps from 1.000 to 1.250 (3AG1-250-5CL) for the bolt length but you wont need a washer. Would the 1.000 bolt length work?

I believe It will be the same bolt but longer as the ones I used for the flexplate. I'm not sure how big the actual bolt head is. I have a couple extra. I'll see if I can get a measurement today.




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Turbo 3800 E85 F23 5spd spec5
11.17@132.6

[This message has been edited by Justinbart (edited 01-11-2013).]

Let me know what that head height is. a 1 inch bolt going thru the .470" flywheel leaves me .530". Divide that by 5/16 = 1.7X Dia. That should work out just fine with loctite. Do you know off hand what 'grade' the ARP bolt is so that tightening torque can be calculated?

According to:
http://www.fastenal.com/con...0Gr5%20Gr8%20Gr9.pdf

The 5/16"-18 bolt with thread locker has a K-value of .17, and therefore a tightening torque of 294 in-lbs, or 24.5 ft-lbs.

[This message has been edited by Jncomutt (edited 01-11-2013).]

I may be wrong, but I think bolts have a different torque requirement with and without the use of washers?

That would make sense if it affected it acting as a bearing surface. That would, in my opinion, decrease the k-factor, and therefore decrease the torque, which put them closer to what I tightened my last L9 bolts to (19 ft-lbs). The chart above, however, shows even a well lubricated bolt should be tightened to 21.5 ft-lbs.

[This message has been edited by Jncomutt (edited 01-11-2013).]

Those are the 180,000 psi bolts. I torqued to 24 ft-lb with loctite, and put arp molly lube on the bolt head flange. I read for hours of discussions on whether to use molly lube or loctite on the threads and ended on loctite for the threads with lube on the head.

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Turbo 3800 E85 F23 5spd spec5
11.17@132.6

Sorry it took me so long. I kept forgetting about it. The bolt head is "0.300

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Turbo 3800 E85 F23 5spd spec5
11.17@132.6

Thank you for taking the time to get that measurement. The 1" bolt (-.470") would leave .530" of thread, or just over 1.5x Dia. thread engagement, it should work just fine if properly torqued. Jumping up to a 1.25" bolt with no washer puts me at 2.5x dia., which isn't a problem if the crank is tapped over 3/4" deep. I haven't measured that yet.

EDIT:
Just realized the bolts I'm using are .234" head + .060" washer = .294", or roughly .300" depending on washer thickness tolerance.

[This message has been edited by Jncomutt (edited 01-15-2013).]

Bringing this back from months ago, I did more measuring and it turns out my SPEC flywheel + washer is only about .540". I also measured the depth of the bolt holes on the crank. It appears they are 'roughly' drilled 3/4" deep, and tapped 5/8" deep.

.540" + .625" = 1.165" Max length of the bolt. That means that the best we can do is a 1" bolt. A 1" bolt, with .540" of flywheel/washer leaves .460" available thread and 1.47x dia. thread engagement, assuming no lead in chamfer on the crank. A 1" flanged bolt would be opposite and leave .540" available. This would result in 1.7x dia. engagement.

A stock steel flywheel is approx. .360" thick. A 1" bolt will leave .640" of thread remaining, too deep for the .625" tap. It seems a flanged 1" bolt, similar the ARP will need to be massaged slightly. A 1" hex bolt with washer should work perfect.

[This message has been edited by Jncomutt (edited 04-03-2013).]

Any updates on the new bolts and how they are working with 525HP?